Agricultural and Food Scince in Finland, Vol 10 (2001) Supplement 1 1 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Non-wood plants as raw material for pulp and paper Katri Saijonkari-Pahkala MTT Agrifood Research Finland, Plant Production Research FIN-31600 Jokioinen, Finland, e-mail: katri.pahkala@mtt.fi ACADEMIC DISSERTATION To be presented, with the permission of the Faculty of Agriculture and Forestry, University of Helsinki, for public criticism at Infokeskus Korona, Auditorium 1, on November 30, 2001, at 12 o’clock. mailto:katri.pahkala@mtt.fi Supervisors: Professor Pirjo Peltonen-Sainio Plant Production Research MTT Agrifood Research Finland Jokioinen, Finland Professor Timo Mela Plant Production Research MTT Agrifood Research Finland Jokioinen, Finland Reviewers: Dr. Staffan Landström Swedish University of Agricultural Sciences Umeå, Sweden Professor Bruno Lönnberg Laboratory of Pulping Technology Åbo Akademi University Turku, Finland Opponent: Dr. Iris Lewandowski Department of Science, Technology and Society Utrecht University Utrecht, the Netherlands Custos: Professor Pirjo Mäkelä Department of Applied Biology University of Helsinki Helsinki, Finland 3 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. “A new fiber crop must fit the technical requirements for processing into pulp of acceptable quality in high yield and must also be adaptable to practical agricul- tural methods and economically produce high yield of usable dry matter per acre”. Nieschlag et al. (1960) KSP 2001 5 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Preface The present study was carried out at the MTT Agrifood Research Finland between 1990 and 2000. I wish to extend my gratitude to the Directors of the Crop Science Department, Professor Emeritus Timo Mela and his successor Professor Pirjo Peltonen-Sainio for offering me the financial and insti- tutional framework in which to do this research. The encouragement and friendly support of Profes- sor Pirjo Peltonen-Sainio made it possible to complete this thesis. I also wish to thank Professor Pirjo Mäkelä, for her contribution during the last stages of the work. I am also grateful to Professor Eija Pehu, the former teacher of my subject at the University of Helsinki for her suggestion to work for this thesis. I wish to thank Professor Bruno Lönnberg of Åbo Akademi University and Dr. Staffan Landström of the Swedish Agricultural University, for their valuable advice and constructive criticism. I am grateful to the staff of the Crop Science Department of MTT for the excellent technical assistance in the numerous field experiments and botanical analyses. I also wish to thank the staff of MTT research stations in Laukaa, Ylistaro, Tohmajärvi, Ruukki, Sotkamo and Rovaniemi and the Kotkaniemi Research Station of Kemira Agro for the skilful field work and data collection during the study. Staff of the Chemistry Laboratory of MTT and the Finnish Pulp and Paper Research Insti- tute (KCL) analysed the material obtained from the experiments and whose work I greatly appreci- ate. Special thanks are due to biometrician Lauri Jauhiainen, M.Sc., for statistical consultation and to Mr. Eero Miettinen, M.Sc., for helping in processing the yield data from the variety trials. The English manuscript was revised by Dr. Jonathan Robinson to whom I express my apprecia- tion for his work. I would also like to thank the Editorial Board of the Agricultural and Food Science in Finland for accepting this study for publication in their journal. The members of MTT biomass and reed canary grass group, Anneli Partala, M.Sc., Mia Sah- ramaa, M.Sc., Antti Suokannas, M.Sc. and Mr. Mika Isolahti have provided support during the course of this work. My colleagues Dr. Kaija Hakala and Dr. Hannele Sankari have given good advice on avoiding stress in completing this work. I extend my warm thanks to all of them. Financial support was provided by the Foundation of Technology and is gratefully acknowledged. Finally, my warmest thanks are due to my dear and patient family and my parents Mirjam and Arvo Saijonkari. Jokioinen, October 2001 Katri Saijonkari-Pahkala 6 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Contents List of abbreviations ................................................................................................. 8 Glossary of technical terms ...................................................................................... 8 1 Introduction ......................................................................................................... 11 2 Review of relevant literature on papermaking from field crops ..................... 12 2.1 Global production of non-wood pulp and paper ...................................... 12 2.2 Candidate non-wood plant species for papermaking ............................... 14 2.3 Properties of non-wood plants as raw material for paper ....................... 15 2.3.1 Fibre morphology in non-wood plants used in papermaking ........ 15 2.3.2 Chemical composition ....................................................................... 18 2.4 Possibilities for improving biomass yield and quality by crop management ................................................................................................. 24 2.4.1 Timing of harvest ............................................................................... 24 2.4.2 Plant nutrition .................................................................................... 25 2.4.3 Choice of cultivar .............................................................................. 26 2.5 Pulping of field crops ................................................................................. 26 2.5.1 Pretreatment of the raw material ...................................................... 27 2.5.2 Commercial and potential methods for pulping non-woody plants ................................................................................................... 27 3 Objectives and strategy of the study ................................................................. 29 4 Materials and methods ........................................................................................ 33 4.1 Establishment and management of field experiments ............................. 33 4.2 Sampling ...................................................................................................... 33 4.3 Measuring chemical composition of the plant material .......................... 33 4.4 Pulp and paper technical measurements ................................................... 34 4.5 Methods used in individual experiments .................................................. 34 4.5.1 Selection of plant species .................................................................. 34 4.5.2 Crop management research ............................................................... 35 4.5.3 Reed canary grass variety trials ........................................................ 37 4.6 Statistical methods ...................................................................................... 39 4.7 Climate data ................................................................................................. 40 5 Results .................................................................................................................. 40 5.1 Selecting plant species ............................................................................... 40 5.2 Effect of crop management on raw material for non-wood pulp ............ 41 5.2.1 Harvest timing, row spacing and fertilizer use ............................... 41 5.2.1.1 Reed canary grass ................................................................ 41 5.2.1.2 Tall fescue ............................................................................. 50 5.2.2 Age of reed canary grass ley ............................................................ 58 7 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 5.2.3 Sowing time of reed canary grass .................................................... 62 5.2.4 Timing and stubble height of delayed harvested reed canary grass ........................................................................................ 65 5.3 Research on reed canary grass varieties ................................................... 69 5.3.1 Commercial cultivars of reed canary grass at delayed harvesting 69 5.3.2 Mineral and fibre content of plant parts in reed canary grass cultivars .................................................................................... 73 6 Discussion ............................................................................................................ 77 6.1 Strategy used for selecting species for non-wood pulping ..................... 78 6.2 The preconditions for production of acceptable raw material for non-wood pulping ................................................................................. 78 6.2.1 Possibilities to enhance yielding ability .......................................... 78 6.2.2 Development of crop management practices targeting high quality 81 6.2.3 Possibilities for reducing production costs ..................................... 84 6.2.4 Requirements and possibilities for domestic seed production ...... 84 6.2.5 Enhanced adaptability of reed canary grass to Finnish growing conditions ........................................................................................... 84 6.3 Feasibility of non-wood pulping ............................................................... 85 7 Conclusions ......................................................................................................... 87 8 References ............................................................................................................ 89 Selostus ...................................................................................................................... 95 Appendix I ................................................................................................................. 97 8 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper List of abbreviations AAS flame atomic absorption spectrometer CSF Canadian standard of freeness, measure of drainage CWT cell wall thickness DM dry matter ICP inductively coupled plasma spectrometry KCL The Finnish Pulp and Paper Research Institute LW length weightened fibre length NPK nitrogen-phosphorus-potassium RCG reed canary grass TAPPI Technical Association of the Pulp and Paper Industry Glossary of technical terms Black liquor The waste liquor from the kraft pulping process after pulping containing inorganic elements and dissolved organic material from raw material. Bleaching A treatment of pulps with chemical agents to increase pulp brightness. Brightness A term for describing the whiteness of pulp or paper on scale from 0% (black) to 100%. MgO standard has an absolute brightness of about 96%. Coarseness Oven-dry mass of fibre per unit length of fibre mg m-1. CWT index Cell wall thickness index is indexed value of cell wall thickness measured by the Kajaani FiberLab Analyzer. Delignification A process of breaking down the chemical structure of lignin and rendering it soluble in an alkaline liquid. Dicotyledon Plants with two cotyledons. Drainage Drainage is ease of removing water from pulp fibre slurry. Fibre Plant fibres are composed of sclerenchyma cells with narrow, elongated form with lignified walls. Fibre length The average fibre length is a statistical average length of fibres in pulp meas- ured microscopically or by optical scanner (number average) or classifica- tion with screens (weight average). The weight average fibre length (LW) is equal or larger than the number average fibre length (NW). Fines Small particles other than fibres found in pulps. They originate from differ- ent vessel elements, tracheids, parenchyma cells, sclereids and epidermis. Hardwood Wood produced by deciduous trees. Kappa number A measure of lignin content in pulp. Higher kappa numbers indicate higher lignin content. 9 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Monocotyledons Plants with one cotyledon, for example grass plants. Opacity The ability of paper to hide or mask a color or object in back of the sheet. High opacity results in less transparency and it is important in printing pa- pers. Paper Paper consists of a web of pulp fibres originated from wood or other plants from which lignin and other non-cellulosic components are separated by cook- ing them with chemicals in high temperature. Fine paper is intended for writ- ing, typing, and printing purposes. Pulp An aggregation of the cellulosic fibres liberated from wood or other plant materials physically and/or chemically such that discrete fibres can be dis- persed in water and reformed into a web. Pulping A process whereby the fibres in raw material are separated with chemicals or by mechanical treatment Pulp viscosity A measure of the average chain length of cellulose (the degree of polymeri- zation). Higher viscosity indicates stronger pulp and paper. Pulp yield The amount of material (% of dry matter) recovered after pulping compared to the amount of material before the process. Recovery of pulping A process in which the inorganic chemicals used in pulping are chemicals recovered and regenerated for reuse. Residual alkali The level of residual alkali after completion of cooking determines the final pH of the liquor. If pH is much lower than 12, it indicates lignin deposition in pulp. Screenings Unsufficiently delignified material retained on a Serla Screen laboratory screen with for example 0.25 mm slots. Softwood Wood produced by conifers. Stiffness Stiffness tests measure how paper resist the bending when handled. Tear The energy required to propagate an initial tear through several sheets of paper for a fixed distance. The value is reported in g-cm/sheet. Tensile strength of A measure of the hypothetical length of paper that just supports its own weight paper when supported at one end. It is measured on paper strips 20 cm long by 15– 25 mm wide. 10 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Non-wood plants as raw material for pulp and paper Katri Saijonkari-Pahkala MTT Agrifood Research Finland, Plant Production Research, FIN-31600 Jokioinen, Finland, e-mail: katri.pahkala@mtt.fi This study was begun in 1990 when there was a marked shortage of short fibre raw material for the pulp industry. During the last ten years the situation has changed little, and the shortage is still appar- ent. It was estimated that 0.5 to 1 million hectares of arable land would be set aside from cultivation in Finland during this period. An alternative to using hardwoods in printing papers is non-wood fibres from herbaceous field crops. The study aimed at determining the feasibility of using non-wood plants as raw material for the pulp and paper industry, and developing crop management methods for the selected species. The properties considered important for a fibre crop were high yielding ability, high pulping quality and good adaptation to the prevailing climatic conditions and possibilities for low cost production. A strategy and a process to identify, select and introduce a crop for domestic short fibre production is described in this thesis. The experimental part of the study consisted of screening plant species by analysing fibre and mineral content, evaluating crop management methods and varieties, resulting in description of an appropriate cropping system for large-scale fibre plant production. Of the 17 herbaceous plant spe- cies studied, monocotyledons were most suitable for pulping. They were productive and well adapted to Finnish climatic conditions. Of the monocots, reed canary grass (Phalaris arundinacea L.) and tall fescue (Festuca arundinacea Schreb.) were the most promising. These were chosen for further stud- ies and were included in field experiments to determine the most suitable harvesting system and fertilizer application procedures for biomass production. Reed canary grass was favoured by delayed harvesting in spring when the moisture content of the crop stand was 10–15% of DM before production of new tillers. When sown in early spring, reed canary grass typically yielded 7–8 t ha-1 within three years on clay soil. The yield exceeded 10 t ha-1 on organic soil after the second harvest year. Spring harvesting was not suitable for tall fescue and resulted in only 37–54% of dry matter yields and in far fewer stems and panicles than harvested during the growing season. The economic optimum for fertilizer application rate for reed canary grass ranged from 50 to 100 kg N ha-1 when grown on clay soil and harvested in spring. On organic soil the fertilizer rates needed were lower. If tall fescue is used for raw material for paper, fertilizer application rates higher than 100 kg N ha-1 were not of any additional benefit. It was possible to decrease the mineral content of raw material by harvesting in spring, using moderate fertilizer application rates, removing leaf blades from the raw material and growing the crop on organic soil. The fibre content of the raw material increased the later the crop was harvested, being highest in spring. Removing leaf blades and using minimum fertilizer application rates in- creased the fibre content of biomass. Key words: field crop, dry matter yield, harvest, fertilizer, mineral content, fibre, pulping, papermak- ing, reed canary grass, Phalaris arundinacea, tall fescue, Festuca arundinacea 11 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Paper consists of a web of pulp fibres derived from wood or other plants from which lignin and other non-cellulose components are separated by cooking them with chemicals at high tempera- ture. In the final stages of papermaking an aque- ous slurry of fibre components and additives is deposited on a wire screen and water is removed by gravity, pressing, suction and evaporation (Biermann 1993). The fibre properties of the raw material affect the quality and use of the paper. For fine papers, both long and short fibres are needed. The long fibres from softwoods (conif- erous trees, fibre length 2–5 mm) or from non- woody species such as flax (Linum usitatissi- mum L.), hemp (Cannabis sativa L.) and kenaf (Hibiscus cannabinus L.), of fibre length 28 mm, 20 mm and 2.7 mm, respectively, form a strong matrix in the paper sheet. The shorter hardwood fibres (deciduous trees, fibre length 0.6–1.9 mm) or grass fibres (fibre length 0.7 mm) (Hurter 1988) contribute to the properties of pulp blends, especially opacity, printability and stiffness. In fine papers, short-fibre pulp contributes to good printability. The principal raw material for pa- permaking nowadays is wood derived from var- ious tree species. The main domestic raw materials for fine paper are the hardwood birch (Betula spp.) and softwood conifers, usually spruce (Picea abies L.) and Scots pine (Pinus silvestris L.). Birch pulp in fine paper accounts for more than 60% of all fibre material. However, birch contributes less than 10% to the total forested area in Fin- land (Aarne 1993, Tomppo et al. 1998). The prin- cipal tree species are spruce and Scots pine. The importation of birch for the Finnish paper indus- try increased during the 1990s from 3.5 to 6.5 million/m3 and currently exceeds consumption of domestic hardwood (Sevola 2000). One al- ternative to using birch for printing papers is to use non-wood fibres from herbaceous field crops, as are used in many countries where wood is not available in sufficient quantities. Promising non- woody species for fibre production have been found in the plant families Gramineae, Legumi- nosae and Malvaceae (Nieschlag et al. 1960). Of these, most attention in recent years has been focused on grasses and other monocotyledons (Kordsachia et al. 1992, Olsson et al. 1994) as well as on flax and hemp (van Onna 1994). Dur- ing the beginning of the 1990s, the MTT Agri- food Research Finland and the University of Helsinki, together with the Finnish Pulp and Paper Research Institute, set out to identify the most promising crop species as raw materials for papermaking. The properties considered impor- tant were fibre yield and quality and the mineral composition of the plant material. In those stud- ies, reed canary grass (Phalaris arundinacea L.), tall fescue (Festuca arundinacea Schreb.), mead- ow fescue (F. pratensis L.), goat’s rue (Galega orientalis L.) and lucerne (Medicago sativa L.) were chosen for further study. Field experiments were conducted to determine the optimal harvest- ing system and fertilizer requirements for bio- mass production (Pahkala et al. 1994). During the preliminary stages an intensive research and development programme was be- gun, covering the entire processing chain, from raw material production to the end product. The aim of this agrofibre project, named “Agrokui- dun tuotanto ja käyttö Suomessa – Agrofibre production for pulp and paper” was to develop economically feasible methods for producing specific short-fibre raw material from field crops available in Finland and process it for use in high quality paper production. The project included five components and was carried out between 1993 and 1996. The Ministry of Agriculture and Forestry of Finland financed the project. The five components were: 1. Crop production (crop species, management methods and variety research): MTT (Agrifood Research Finland) and Uni- versity of Helsinki 2. Technology (harvesting, pretreatment, stor- age methods and production costs): MTT, University of Helsinki and Work Effi- ciency Association 1 Introduction 12 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper 3. Pulp cooking and quality (cooking and bleaching methods): KCL (The Finnish Pulp and Paper Research Institute) and Åbo Akademi University 4. Pretreatment of raw material (biotechnolog- ical pretreatment and by-products): University of Helsinki and VTT (Technical Research Centre of Finland) 5. Paper processing (recycling of chemicals, en- vironmental influences, technological poten- tial of non-wood fibres, logistics and eco- nomic analysis): Jaakko Pöyry Oy Methods developed in the project were ap- plied in September 1995, when bleached reed canary grass pulp was produced on a pilot scale (Paavilainen et al. 1996a). The pulp was mixed with pine pulp and made into paper on the pilot paper machine of KCL. The printability of coat- ed and uncoated agro-based fine paper was test- ed in offset printing. The present study describes the crop produc- tion experimentation of the agrofibre project outlined above. The aim was to determine the suitability of field crops as raw material for the pulp and paper industry, and to develop crop management methods for the selected species. The experimental part of the study consisted of screening the plant species by analysing fibre and mineral content, and evaluation of crop manage- ment methods and varieties. The outcome was description of an appropriate cropping system for large-scale fibre plant production. 2 Review of relevant literature on papermaking from field crops 2.1 Global production of non-wood pulp and paper The earliest information on the use of non-woody plant species as surfaces for writing dates back to 3000 BC in Egypt, where the pressed pith tis- sue of papyrus sedge (Cyperus papyrus L.) was the most widely used writing material. Actual papermaking was discovered by a Chinese, Ts’ai Lun, in AD 105, when he found a way of mak- ing sheets using fibres from hemp rags and mul- berry (Morus alba L.). Straw was used for the first time as a raw material for paper in 1800, and in 1827 the first commercial pulp mill be- gan operations in the USA using straw (Atchison and McGovern 1987). In the 1830s, Anselme Payen found a resistant fibrous material that ex- isted in most plant tissues. This was termed cel- lulose by the French Academy in 1839 (Hon 1994). After the invention of new chemical pulp- ing methods paper could also be made from wood. This became the main raw material for paper production in the 20th century. In many countries wood is not available in sufficient quantities to meet the rising demand for pulp and paper (Atchison 1987a, Judt 1993). In recent years, active research has been under- taken in Europe and North America to find a new, non-wood raw material for paper production. The driving force for searching for new pulp sources was twofold: the shortage of short-fibre raw material (hardwood) in Nordic countries, which export pulp and paper and, parallel overproduc- tion of agricultural crops. At the same time, the consumption of paper, especially fine paper, con- tinued to grow, increasing the demand for short fibre pulp (Paavilainen 1996). Commercial non-wood pulp production has been estimated to be 6.5% of the global pulp production and is expected to increase (Paavi- lainen 1998). China produces 77% of the world’s non-wood pulp (Paavilainen et al. 1996b, Paavi- lainen 1998) (Fig. 1). In China and India over 70 % of raw material used by the pulp industry 13 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. comes from non-woody plants (Fig. 1). The main sources of non-wood raw materials are agricul- tural residues from monocotyledons, including cereal straw and bagasse, a fibrous residue from processed sugar cane (Saccharum officinarum L.) (Fig. 2). Bamboo, reeds and some grass plants are also grown or collected for the pulp industry (Paavilainen et al. 1996b). The main drawbacks that are considered to limit the use of non-wood fibres are certain dif- ficulties in collection, transportation and stor- age (McDougall et al. 1993, Ilvessalo-Pfäffli 1995). However, data from Finland show that the transport costs of grass fibre are not critical for the raw material production chain, where they constitute only 14% of the total costs (Hemming et al. 1996). In the case of grass fibres, the high content of silicon (Ilvessalo-Pfäffli 1995) im- pliess extra costs, as it wears out factory instal- lations (Watson and Gartside 1976), lowers pa- Fig. 1. Global production of non- wood pulps. The figure reprinted with kind permission from Lee- na Paavilainen. Translated from Paavilainen et al. (1996b). Fig. 2. Consumption of non-wood pulps in paper production from different raw materials. The figure reprinted with kind permission from Leena Paavilainen. Translat- ed from Paavilainen et al. (1996b). 14 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper per quality (Jeyasingam 1988) and complicates recovery of chemicals and energy in papermak- ing (Ranua 1977, Keitaanniemi and Virkola 1982, Ulmgren et al. 1990). 2.2 Candidate non-wood plant species for papermaking Plant species currently used for papermaking belong to the botanical division Spermatophyta (seed plants), which is divided into two divisions, Angiospermae (seeds enclosed within the fruit) and Gymnospermae (naked seeds), the latter in- cluding the class Coniferae. Angiospermae in- clude two classes, Monocotyledonae and Dicot- yledonae (Fig. 3). The most common plant spe- cies used for papermaking are coniferous trees of the Gymnospermae and deciduous trees of the Dicotyledonae. Non-wood papermaking plants, such as grasses and leaf fibre plants, belong to the class Monocotyledonae and bast fibre and fruit fibre plants are dicotyledons (Ilvessalo- Pfäffli 1995). Promising new non-wood species for fibre production have been identified in earlier re- search on the plant families Gramineae, Legu- minosae and Malvaceae (Nieschlag et al. 1960, Nelson et al. 1966). In northern Europe particu- lar interest in recent years has focused on grass- es and other monocotyledons (Olsson 1993, Mela et al. 1994). Of several field crops studied, reed canary grass has been one of the most promis- ing species for fine paper production in Finland and Sweden (Berggren 1989, Paavilainen and Torgilsson 1994). Other grasses, such as tall fes- cue (Festuca arundinacea Schr.) (Janson et al. 1996a), switchgrass (Panicum virgatum L.) (Ra- diotis et al. 1996) and cereal straw (Atchison 1988, Lönnberg et al. 1996) can be used for pa- per production. In central Europe, elephant grass (Miscanthus sinensis Anderss.) has been stud- ied as a raw material for paper and energy pro- duction (Walsh 1997). A new fibre crop must fit the technical re- quirements for processing into pulp of accepta- ble quality. It must also be adaptable to practi- cal agricultural methods and produce adequate dry matter (DM) and fibre yield at economical- ly attractive levels (Nieschlag et al. 1960, Atchison 1987b). There must also be a sufficient supply of good quality raw material for running the process throughout the year (Atchison 1987b). It has been shown that non-wood spe- cies have high biomass production capacity and the pulp yields obtained have in most cases been higher than those from wood species (Table 1). Fig. 3. The taxonomy of fibre plants. Adapted from Ilvessalo-Pfäffli (1995). 15 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 2.3 Properties of non-wood plants as raw material for paper Analysis of fibre morphology and chemical com- position of plant material has been useful in searching for candidate fibre crops. This has af- forded an indication of the papermaking poten- tial of various species (Muller 1960, Clark 1965). The properties of the fibre depend on the type of cells from which the fibre is derived, as the chemical and physical properties are based on the cell wall characteristics (McDougall et al. 1993). Anatomically, plant fibres are composed of narrow, elongated sclerenchyma cells. Mature fibres have well-developed, usually lignified walls and their principal function is to support, and sometimes to protect the plant. Fibres de- velop from different meristems (Fig. 4), and they are found mostly in the vascular tissue of the plant, but sometimes also occur in other tissues (Esau 1960, Fahn 1974). Table 1. Annual dry matter (DM) and pulp yields of various fibre plants. DM yield Pulp yield Plant species t ha-1 t ha-1 Reference Wheat straw 1)2.5 2)1.1 FAO 1995, Pahkala et al. 1994 Oat straw 1)1.6 2)0.7 FAO 1995, Pahkala et al. 1994 Rye straw 1)2.2 2)1.1 FAO 1995, Pahkala et al. 1994 Barley straw 1)2.1 2)1.9 FAO 1995, Pahkala et al. 1994 Rice straw 3 3)1.2 Paavilainen & Torgilsson 1994 Bagasse (sugar cane waste) 9 3)4.2 Paavilainen & Torgilsson 1994 Bamboo 4 3)1.6 Paavilainen & Torgilsson 1994 Miscanthus sinensis 12 3)5.7 Paavilainen & Torgilsson 1994 Reed canary grass 6 3)3.0 Paavilainen et al. 1996b, Pahkala et al. 1996 Tall fescue 8 2)3.0 Pahkala et al. 1994 Common reed 9 2)4.3 Pahkala et al. 1994 Kenaf 15 3)6.5 Paavilainen & Torgilsson 1994 Hemp 12 3)6.7 Paavilainen & Torgilsson 1994 Temperate hardwood (birch) 3.4 3)1.7 Paavilainen & Torgilsson 1994 Fast growing hardwood (eucalyptus) 15.0 3)7.4 Paavilainen & Torgilsson 1994 Scandinavian softwood (coniferous) 1.5 3)0.7 Paavilainen & Torgilsson 1994 1) The dry matter yield for cereal straw is estimated by using the harvest index of 0.5. 2) Pulp process soda-anthraquinone 3) Average values, pulping method unmentioned 2.3.1 Fibre morphology in non-wood plants used in papermaking Morphological characteristics, such as fibre length and width, are important in estimating pulp quality of fibres (Wood 1981). In fibres suitable for paper production, the ratio of fibre length to width is about 100:1, whereas in tex- tile fibres the ratio is more than 1000:1. In co- niferous trees this ratio is 60–100:1, and in de- ciduous trees 2–60:1 (Hurter 1988, Hunsigi 1989, McDougall et al. 1993). Fibre length and width of non-woody species vary depending on plant species and the plant part from which the fibre is derived (Ilvessalo-Pfäffli 1995). The average fibre length ranges from 1 mm to 30 mm, being shortest in grasses and longest in cotton. The average ratios of fibre length to diameter range from 50:1 to 1500:1 in non-wood species (Table 2) (Hurter 1988). Lumen size and cell wall thickness affect the rigidity and strength of the papers made from the fibres. Fibres with a large 16 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper lumen and thin walls tend to flatten to ribbons during pulping and papermaking, giving good contact between the fibres and consequently hav- ing good strength characteristics (Wood 1981). Softwood fibres from coniferous trees are ideal for papermaking since their long, flexible struc- ture allows the fibres to pack and reinforce the sheets. Hardwoods from deciduous trees have shorter, thinner and flexible fibres that pack tightly together and thus produce smooth and dense paper (Hurter 1988, Fengel and Wegener 1989, McDougall et al. 1993). Non-wood plant fibres can be divided into several groups depending on the location of the fibres in the plant. Ilvessalo-Pfäffli (1995) has described four fibre types: grass fibres, bast fi- bres, leaf fibres and fruit fibres. Grass fibres are also termed stalk or culm fibres (Hurter 1988, Judt 1993) (Table 2). Grass fibres Grass fibres currently used for papermaking are obtained mainly from cereal straw, sugarcane, reeds and bamboo (Atchison 1988). The fibre material of these species originates from the xylem in the vascular bundles of stems and leaves. It also occurs in separate fibre strands, which are situated on the outer sides of the vas- cular bundles or form strands or layers that ap- pear to be independent of the vascular tissues (Esau 1960, McDougall et al. 1993, Ilvessalo- Pfäffli 1995). Vascular bundles can be distribut- ed in two rings as in cereal straw and in most temperate grasses, with a continuous cylinder of sclerenchyma close to the periphery. The bun- dles can also be scattered throughout the stem section as in corn (Zea mays L.), bamboo and sugarcane (Esau 1960). The average length of grass fibres is 1–3 mm (Robson and Hague 1993, Ilvessalo-Pfäffli 1995) and the ratio of fibre length to width varies from 75:1 to 230:1 (Table 2) (Hurter 1988). Wheat (Triticum aestivum L.) is the mono- cotyledon that is used most in commercial pulp- ing. However, fibres from rye (Secale cereale L.), barley (Hordeum vulgare L.) and oat (Avena sati- va L.) are similar to those of wheat (Ilvessalo- Pfäffli 1995) and they could also be used in pa- permaking. Rice straw (Oryza sativa L.) is used in Asia and Egypt. Bagasse is one of the most important agricultural residues used for pulp manufacture. Bagasse pulp is used for all grades of papers (Atchison 1987b). Some reeds (Phrag- mites communis Trin., Arundo donax L.) are collected and used in mixtures with other fibres Fig. 4. Schematic representation of a) the location of fibres in stem and leaves of monocotyledonous plants (McDou- gal et al. 1993), reprinted with kind permission of John Wi- ley & Sons Ltd and b) primary and secondary cell walls (Taiz and Zeiger 1991). 17 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. in Asia and in South America as raw material for writing and printing papers. In the case of esparto (Stipa tenecissima L.), only leaves are used, whereas bamboo pulp is commonly made from the pruned stem and bagasse pulp from sugarcane waste. When grass species are pulped for papermaking, the entire plant is usually used and the pulp contains all the cellular elements of the plant (Ilvessalo-Pfäffli 1995). The propor- tion of fibre cells in commercial grass pulp can be 65 to 70% by weight (Gascoigne 1988, Ilves- salo-Pfäffli 1995). In addition to fibre cells, the grass pulp also contains small particles (fines) from different vessel elements, tracheids, paren- chyma cells, sclereids and epidermis, which make the grass pulp more heterogeneous than wood pulp, in which all the fibres originate from the stem xylem. Most of the fines lower the drainage of the pulp and thus the drainage time in papermaking is longer (Wisur et al. 1993). However, the amount of fines decreases if the leaf fraction, the main source of the fines, can be restricted to only the straw component of the grass. Bast fibres Bast fibres refer to all fibres obtained from the phloem of the vascular tissues of dicotyledons (TAPPI Standard T 259 sp-98 1998). Fibre cells occur in strands termed fibres (Esau 1960, Il- vessalo-Pfäffli 1995). Hemp, kenaf, ramie (Boechmeria nivea L.) and jute (Corchorus cap- sularis L.) fibres are derived from the second- ary phloem located in the outer part of the cam- bium. In flax, fibres are mainly cortical fibres in the inner bark, on the outer periphery of the vas- cular cylinder of the stem (Esau 1960, McDou- gall et al. 1993, Ilvessalo-Pfäffli 1995). In these plants the length of the fibre cells varies from 2 mm (jute) to 120 mm (ramie) (Esau 1960, Ilves- salo-Pfäffli 1995). Flax fibres consist of up to 40 fibres in bundles of 1 m length. Hemp fibres are coarser than those of flax, with up to 40 fi- bres in bundles that can be 2 m in length (Mc- Dougall et al. 1993). Bast fibres must be isolat- ed from the stem by retting whereby micro-or- ganisms release enzymes that digest the pectic material surrounding the fibre bundles, thus free- ing the fibres. With ramie, boiling in alkali is required (McDougall et al. 1993). Bast fibres are used as raw material for paper when strength, permanence and other special properties are needed. Examples include lightweight printing and writing papers, currency and cigarette pa- pers (Atchison 1987b, Kilpinen 1991, Ilvessalo- Pfäffli 1995). Leaf fibres Leaf fibres are obtained from leaves and leaf sheaths of several monocotyledons, tropical and subtropical species (McDougall et al. 1993, Il- vessalo-Pfäffli 1995). Strong Manila hemp, or acaba, is derived from leaf sheaths of Musa tex- tilis L., and is mainly used in cordage and for making strong but pliable papers. Sisal is pro- duced from vascular bundles of several species in the genus Agave, notably A. sisalana Perrine (true sisal) and A. foucroydes Lemaire (hene- quen) (McDougall et al. 1993). Leaves of espar- to grass produce a fibre used to make soft writ- ing papers (McDougall et al. 1993). Fruit fibres Fruit fibres are obtained from unicellular seed or fruit hairs. The most important is cotton fi- bre, formed by the elongation of individual epi- dermal hair cells in seeds of various Gossypium species (McDougall et al. 1993). The longest fi- bres of cotton (lint) are used as raw material for the textile industry, but the shorter ones (linters, 2–7 mm long), as well as textile cuttings and rags, are used as raw material for the best writ- ing and drawing papers (Ilvessalo-Pfäffli 1995). Kapok is a fibre produced from fruit and seed hairs of two members of the family Bombaceae: Eriodendron anfractuosum DC. (formerly Ceiba pentandra Gaertn.) produces Java kapok and Bombax malabaricum DC. produces Indian ka- pok. Kapok fibres originate from the inner wall of the seed capsule. The cells are relatively long, up to 30 mm, with thin and highly lignified walls and a wide lumen (McDougall et al. 1993). 18 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper 2.3.2 Chemical composition Chemical composition of the candidate plant gives an idea of how feasible the plant is as raw material for papermaking. The fibrous constitu- ent is the most important part of the plant. Since plant fibres consist of cell walls, the composi- tion and amount of fibres is reflected in the prop- erties of cell walls (Hartley 1987, McDougall et al. 1993). Cellulose is the principal component in cell walls and in fibres. The non-cellulose components of the cell wall include hemicellu- loses, pectins, lignin and proteins, and in the epidermal cells also certain minerals (Hartley 1987, Taiz and Zeiger 1991, Philip 1992, Cass- ab 1998). The amount and composition of the cell wall compounds differ among plant species and even among plant parts, and they affect the pulping properties of the plant material (McDou- gall et al. 1993). Some of non-woody fibre plants contain more pentosans (over 20%), holocellu- lose (over 70%) and less lignin (about 15%) as compared with hardwoods (Hunsigi 1989). They have also higher hot water solubility, which is apparent from the easy accessibility of cooking liquors. The low lignin content in grasses and annuals lowers the requirement of chemicals for cooking and bleaching (Hunsigi 1989). Except for the fibrous material, plants also consist of other cellular elements, including min- eral compounds. While the inorganic compounds are essential for plant growth and development Table 2. Dimensions of fibres obtained from non-wood species. L = fibre length, D = fibre diameter, L:D = ratio fibre length to fibre diameter (Hurter 1988). Fibre length µm (L) Fibre diameter µm (D) L:D- Source of fibres Max. Min. Average Max. Min. Average ratio Stalk fibres (grass fibres) Cereals -rice 3480 650 1410 14 5 8 175:1 -wheat, rye, 3120 680 1480 24 7 13 110:1 oats, barley, mixed Grasses -esparto 1600 600 1100 14 7 9 120:1 -sabai 4900 450 2080 28 4 9 230:1 Reeds -papyrus 8000 300 1500 25 5 12 125:1 -common reed 3000 100 1500 37 6 20 75:1 -bamboo 3500– 375– 1360– 25–55 3–18 8–30 135– 9000 2500 4030 175:1 -sugar cane 2800 800 1700 34 10 20 85:1 (bagasse) Bast fibres Fibre flax 55000 16000 28000 28 14 21 1350:1 Linseed straw 45000 10000 27000 30 16 22 1250:1 Kenaf 7600 980 2740 20 135:1 Jute 4520 470 1060 72 8 26 45:1 Hemp 55000 5000 20000 50 16 22 1000:1 Leaf fibres Acaba 12000 2000 6000 36 12 20 300:1 Sisal 6000 1500 3030 17 180:1 Fruit or seed fibres Cotton 50000 20000 30000 30 12 20 1500:1 Cotton linters 6000 2000 3500 27 17 21 165:1 Wood fibres Coniferous trees 3600 2700 3000 43 32 30 100:1 Leaf trees 1800 1000 1250 50 20 25 50:1 19 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. (Mitscherlich 1954, Epstein 1965, Marschner 1995), they are undesirable in pulping and pa- permaking (Keitaanniemi and Virkola 1978, Keitaanniemi and Virkola 1982, Jeyasingam 1985, Ilvessalo-Pfäffli 1995). Cellulose Cellulose is the principal component of plant fi- bres used in pulping. It forms the basic structur- al material of cell walls in all higher terrestrial plants being largely responsible for the strength of the plant cells (Philip 1992). Cellulose always has the same primary structure, it is a –1,4 linked polymer of D-glucans (Table 3) (Aspinall 1980, Smith 1993). It occurs in the form of long, linear, ribbon-like chains, which are aggregated into structural fibrils (Fig. 5). Each fibril con- tains from 30 to several hundred polymeric chains that run parallel with the laterally exposed hydroxyl groups. These hydroxyl groups take part in hydrogen bonding, with linkages both within the polymeric molecules and between them. This arrangement of the hydroxyl groups in cellulose makes them relatively unavailable to solvents, such as water, and gives cellulose its unusual resistance to chemical attack, as well as its high tensile strength (Philip 1992). The first layers of cellulose are formed in the primary cell walls during the extension stage of the cell, but most cellulose is deposited in the secondary walls. The proportion of cellulose in primary cell walls is 20 to 30% of DM and in secondary cell walls 45 to 90% (Aspinall 1980). The cellulose content of a plant depends on the cell wall content, which can vary between plant species (Staniforth 1979, Hartley 1987, Hurter 1988) and varieties (Khan et al. 1977, Bentsen and Ravn 1984). The age of the plant (Gill et al. 1989, Grabber et al. 1991) and plant part (Pe- tersen 1989, Grabber et al. 1991, Theander 1991) also affect the cellulose content. Annual plants generally have about the same cellulose content as woody species (Wood 1981), but their higher content of hemicellulose increases the level of pulp yield more than the expected level on the basis of cellulose content alone (Wood 1981). The cellulose and alpha-cellulose contents can be correlated with the yields of unbleached and bleached pulps, respectively (Wood 1981). Hemicellulose Hemicelluloses consist of a heterogeneous group of branched polysaccharides (Table 3). The spe- cific constitution of the hemicellulose polymer depends on the particular plant species and on the tissue. Glucose, xylose and mannose often predominate in the structure of the hemicellu- loses (Philip 1992), and are generally termed glucans, xylans, xyloglucans and mannans (Smith 1993). Xylans are the most abundant non- cellulose polysaccharides in the majority of an- giosperms, where they account for 20 to 30% of the dry weight of woody tissues (Aspinall 1980). They are mainly secondary cell wall components, but in monocotyledons they are found also in the primary cell walls (Burke et al. 1974), represent- ing about 20% of both the primary and second- ary walls. In dicots they amount to 20% of the secondary walls, but to only 5% of the primary cell walls. Xylans are also different in monocots and in dicots (Smith 1993). In gymnosperms, where galactoglucomannans and glucomannans represent the major hemicelluloses, xylans are less abundant (8%) (Timell 1965). The hemicel- luloses in secondary cell walls are associated with the aromatic polymer, lignin. Pectins Pectins, i.e. pectic polysaccharides, are the poly- mers of the middle lamella and primary cell wall of dicotyledons, where they may constitute up to 50% of the cell wall. In monocotyledons, the proportion of pectic polysaccharides is nor- mally less than this and in secondary walls the proportion of hemicellulose polysaccharides greatly exceeds the amount of pectic polysac- charides (Smith 1993). The pectic substances are characterised by their high content of D-galac- turonic acid and methylgalacturonic acid resi- dues (Table 3). Pectins are more important in growing than in non-growing cell walls, and thus they are not a significant constituent in commer- cial fibres (Philip 1992) except in flax fibre, where pectins are found in lamellae between the 20 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Fig. 5. Schematic presentation of the structure of a) cellu- lose (Smith 1993), reprinted with kind permission from John Wiley & Sons Ltd and b) lignin (Nimz 1974), reprinted with kind permission from Wiley-VCH. 21 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. fibres and account for 1.8% of dry weight (Mc- Dougal et al. 1993). Lignin Lignin is the most abundant organic substance in plant cell walls after polysaccharides. Lignins are highly branched phenolic polymers (Fig. 5) and constitute an integral cell wall component of all vascular plants (Grisebach 1981). The structure and biosynthesis of lignins has been widely studied (for a review Grisebach 1981, Lewis and Yamamoto 1990, Monties 1991 and Whetten et al. 1998). The reason for the great interest is the abundance of lignin in nature, as well as its economical importance for mankind. For papermaking, lignin is chemically dissolved because of the separation of the fibres in the raw material. In cattle feeds, lignin markedly lowers the digestibility (Buxton and Russel 1988). Lignins are traditionally considered to be polymers, which are formed from monolignols: p-coumaryl alcohol, coniferyl alcohol, and si- napyl alcohol (Fig. 6). Each of the precursors may form several types of bonds with other pre- cursors in constructing the lignin polymer. A great variation in lignin structure and amount exists among the major plant groups and among species (Sarkanen and Hergert 1971, Gross 1980). Great variation in lignin structure and amount exists also among cell types of different age within a single plant (Table 4) (Albrecht et al. 1987, Buxton and Russel 1988, Jung 1989), and even between different parts of the wall of a single cell (Whetten et al. 1998). The structure and biogenesis of grass cell walls is comprehen- sively described in a review by Carpita (1996). Gymnosperm lignin contains guaiacyl units (G-units), which are polymerized from conifer- yl alcohol, and a small proportion of p-hydrox- yphenyl units (H-units) formed from p-coumar- yl alcohol. Angiosperm lignins are formed from both syringyl units (S-units), polymerized from sinapyl alcohol, and G-units with a small pro- portion of H-units (Sarkanen and Hergert 1971, Whetten et al. 1998). Syringyl lignin increases in proportion relative to guaiacyl and p-hydrox- yphenyl lignins during maturation of some grass- es (Carpita 1996). In grass species the total lignin content varies from 15 to 26% (Higuchi et al. 1967a). For reed canary grass Burritt et al. (1984) found only 1.2%. In grasses and legumes lignins are predominantly formed from coniferyl and sinapyl alcohols with only small amounts of p- coumaryl alcohol (Buxton and Russel 1988). Lignins are considered to contribute to the compressive strength of plant tissue and water Table 3. The principal polysaccharides of the plant cell wall, showing structure of the interior chains. Glc = glucose, Xyl = xylose, Man = mannose, Gal = galactose, Ara = arabinose, Rha = rhamnose, GalA = galacturon acid (Smith 1993). Polysaccharide Interior chain Cellulose -Glc-(1→4)-Glc-(1→4)-Glc-(1→4)- Hemicellulose Xyloglucan -Glc-(1→4)-Xyl-(1→4)-Glc-(1→4)- Xylan -Xyl-(1→4)-Xyl-(1→4)-Xyl-(1→4)- Mannan -Man-(1→4)-Man-(1→4)-Man-(1→4)- Glucomannan -Man-(1→4)-Glc-(1→4)-Man-(1→4)- Callose -Glc-(1→3)-Glc-(1→3)-Glc-(1→3)- Arabinogalactan -Gal-(1→3)-Ara-(1→3)-Gal-(1→3)- Pectins Homogalacturonan -GalA-(1→4)-GalA-(1→4)-GalA-(1→4)- Rhamnogalacturonan -GalA-(1→2)-Rha-(1→4)-GalA-(1→2)- Arabinan -Ara-(1→5)-Ara-(1→5)-Ara-(1→5)- Galactan -Gal-(1→4)-Gal-(1→4)-Gal-(1→4)- 22 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper impermeability of the cell wall. Lignins aid cells in resistance to microbial attack (Taiz and Zeiger 1991, Whetten et al. 1998), but they do not in- fluence the tensile properties of the cell wall (Grisebach 1981). Monolignols can also form bonds with other cell wall polymers in addition to lignin. Cross- linking with polysaccharides and proteins usu- ally results in a very complex three-dimension- al network (Monties 1991, Ralph and Helm 1993, Whetten et al. 1998). This close connection be- tween phenolic polymers and plant cell wall car- bohydrates makes the effective separation and utilization of the fibres more complicated. In woody plants relatively few covalent bonds ex- ist between carbohydrates and lignin compared with those in forage legumes and grasses where the lignin component is also covalently linked to phenolic acids, notably 4-hydroxycinnamic acids, p-coumaric acid and ferulic acid (Mon- ties 1991, Ralph and Helm 1993). Lignin and hemicelluloses fill the spaces between the cel- lulose chains in the cell wall and between the cells themselves. This combined structure gives the plant cell wall and the bulk tissue itself struc- tural strength, and improves stiffness and tough- ness properties (Robson and Hague 1993). Minerals There are 19 minerals that are essential or use- ful for plant growth and development. The mac- ro nutrients, such as N, P, S, K, Mg and Ca are integral to organic substances such as proteins and nucleic acids and maintain osmotic pressure. Their concentrations in plants vary from 0.1 to 1.5% of DM (Epstein 1965). The micro nutri- ents, such as Fe, Mn, Zn, Cu, B, Mo, Cl and Ni, contribute mainly to enzyme production or acti- vation and their concentrations in plants are low (Table 5) (Epstein 1965, Marschner 1995). Sili- con (Si) is essential only in some plant species. The amount of silicon uptake by plants is de- scribed by silica (SiO 2 ) concentration. The high- est silica concentrations (10–5%) are found in Equisetum-species and in grass plants growing in water, such as rice. Other monocotyledons, including cereals, forage grasses, and sugarcane contain SiO 2 at 1–3% of DM (Marschner 1995). Si in epidermis cells is assumed to protect the plant against herbivores (Jones and Handreck 1967) and in xylem walls, to strengthen the plant as lignin (Raven 1983). The concentration of a particular mineral substance in a plant varies depending on plant age or stage of development, plant species and the concentration of other min- erals (Tyler 1971, Gill et al. 1989, Marschner 1995) as well as the plant part (Rexen and Munck 1984, Petersen 1989, Theander 1991). In the pulping process the minerals of the raw material are considered to be impurities and should be removed during pulping or bleaching (Misra 1980). The same elements are found both in non-woody and in woody species, but the con- centrations are lower in woody plants (Hurter 1988) (Table 6). Si is the most deleterious ele- ment in the raw material for pulping, because it complicates the recovery of chemicals and en- ergy in pulp mills (Ranua 1977, Keitaanniemi and Virkola 1982, Rexen and Munck 1984, Je- yasingam 1985, Ulmgren et al. 1990). Si wears out the installations of paper factories (Watson and Gartside 1976) and can lower the paper qual- ity (Jeyasingam 1985). Other harmful elements for the pulping process include K, Cl, Al, Fe, Mn, Mg, Na, S, Ca and N (Keitaanniemi and Virkola 1982). Choosing a suitable plant species Table 4. Weight of the cell wall component and concentration of lignin in stems of grasses and legumes. Adapted from Buxton and Russel (1988). Cell wall g kg-1 Lignin g kg-1 cell wall Lignin % of DM Species Immature Mature Immature Mature Immature Mature Grasses 628 692 74 154 4.6 10.7 Legumes 514 712 212 244 10.9 17.4 23 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Fig. 6. Structures of the three monolignols and the residues derived from them. Radical group is bonded to the oxygen at the 4-position (Lewis and Yamamoto 1990). Reprinted with kind permission from the Annual Review of Plant Physiology & Molecular Biology. Table 5. Concentrations of essential elements in plant species (Epstein 1965, Brown et al. 1987). Element µmol g-1 mg kg-1 Relative number of DM (ppm) % of atoms Mo 0.001 0.1 – 1 Ni c. 0.001 c. 0.1 – 1 Cu 0.10 6 – 100 Zn 0.30 20 – 300 Mn 1.0 50 – 1000 Fe 2.0 100 – 2000 B 2.0 20 – 2000 Cl 3.0 100 – 3000 S 30 – 0.1 30000 P 60 – 0.2 60000 Mg 80 – 0.2 80000 Ca 125 – 0.5 125000 K 250 – 1.0 250000 N 1000 – 1.5 1000000 24 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper as the raw material for pulping can minimise the amount of undesirable minerals in process. Moreover, using only the plant parts that con- tain low amounts of minerals such as Si repre- sents an improvement. 2.4 Possibilities for improving biomass yield and quality by crop management Chemical properties and pulping quality of non- woody plant material fluctuate more than do those of woody species (Judt 1993, Wisur et al. 1993). High variability is mainly due to differ- ences in growing conditions, e.g. soil type, nu- trient level, climate and the developmental stage of the plant at the time of harvest. High DM yield, which is important for the economics of production, is highly affected by management practices such as harvest timing, fertilizer ap- plication, age of the crop stand and choice of the variety. 2.4.1 Timing of harvest Harvest timing and age of the ley influence DM yield of forage crops (Tuvesson 1989, Lomakka Table 6. Content of alpha-cellulose, lignin, pentosan, ash and silica (% of dry matter) in selected fibre plants. Adapted from Hurter (1988). Alpha- Lignin Pentosans Ash SiO 2 Plant species cellulose % % % % % Stalk fibres (grass fibres) Cereals -rice 28–36 12–16 23–28 15–20 9–14 -wheat 29–35 16–21 26–32 4–9 3–7 -oat 31–37 16–19 27–38 6–8 4–7 -barley 31–34 14–15 24–29 5–7 3–6 -rye 33–35 16–19 27–30 2–5 0.5–4 Grasses -esparto 33–38 17–19 27–32 6–8 2–3 -sabai – 17–22 18–24 5–7 3–4 Reeds -common reed 45 22 20 3 2 -bamboo 26–43 21–31 15–26 1.7–5 1.5–3 -bagasse 32–44 19–24 27–32 1.5–5 0.7–3 Bast fibres Fibre flax 45–68 10–15 6–17 2–5 – Linseed straw 34 23 25 2–5 – Kenaf 31–39 15–18 21–23 2–5 – Jute – 21–26 18–21 0.5–1 <1 Leaf fibres Acaba 61 9 17 1 <1 Sisal 43–56 8–9 21–24 0.6–1 <1 Seed and fruit fibres Cotton 85–90 3–3.3 – 1–1.5 <1 Cotton linters 80–85 3–3.5 – 1–2 <1 Wood fibres Coniferous trees 40–45 26–34 7–14 1 <1 Leaf trees 38–49 23–30 19–26 1 <1 25 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 1993, Nissinen and Hakkola 1994). On average, the highest yields are harvested in the second ley year (Tuvesson 1989, Nissinen and Hakkola 1994). Forage grasses were favoured by the two cut system over the three cut one (Nissinen and Hakkola 1994). In Swedish studies, the latitude also influenced yield level when reed canary grass was harvested during the growing period. When it was cut only once, the highest yields in central Sweden were recorded in late July, but in northern Sweden in late September (Tuves- son 1989). When reed canary grass harvest was delayed until the following spring, the first yield was 25% lower than that harvested in August, the second spring yield was the same as in Au- gust and the third spring yield was 1–2 tons high- er than in August (Olsson 1993). Landström et al. (1996) reported increasing yield when reed canary grass was harvested in spring. Harvest timing greatly influences the chem- ical composition of harvested biomass due to the critical effect of the developmental stage. With ageing, the relative amount of cell walls increas- es in plant biomass, because cellulose and lignin deposits increase in the secondary walls (Bux- ton and Hornstein 1986, Buxton and Russel 1988, Gill et al. 1989). Another determining fac- tor of chemical composition in harvested bio- mass is the ratio of stems and leaves that chang- es during the growing season (Muller 1960, Bux- ton and Hornstein 1986, Petersen 1988). The specific effect of harvest timing on min- eral composition of the harvested plant material depends on the particular element and plant age. The concentrations of N, P and K, the main plant nutrients, decrease as the growing season pro- ceeds (Tyler 1971, Cherney and Marten 1982, Gill et al. 1989). The decrease continues during the following winter (Lomakka 1993). The N, P, and K concentrations are lowest in dead plant material harvested in spring (Olsson et al. 1991, Lomakka 1993, Wilman et al. 1994) as is also the case for Ca, Mg and Mn (Lomakka 1993). In contrast, the concentrations of Si, Al and Fe in- crease as the season proceeds (Tyler 1971), be- ing highest in dead plant material in spring (Landström et al. 1996, Burvall 1997). 2.4.2 Plant nutrition Low mineral content in the plant material is pre- ferred for fibre production. However, the unde- sirable elements may be important plant nutri- ents that favour plant growth and yield. Nutri- ents, N and K in particular, are often limiting in plant production and are thus added in the form of fertilizers, resulting in an elevation in their concentration, especially in physiologically ac- tive tissues. Increase in the supply of mineral nutrients from the deficiency range improves the growth of crop plants. The effect of N in partic- ular on yield has been studied widely in arable crops and the highly positive yield response is well known in grasses (MacLeod 1969, Hiivola et al. 1974, Allinson et al. 1992, Gastal and Bé- langer 1993). However, unfavourable conditions such as drought can restrict the yield response (Marschner 1995). The interaction between dif- ferent mineral nutrients is also important. For example, potassium has a greater effect on the intake of N than on P (MacLeod 1969). Yield increase is a result of different processes, includ- ing increase of leaf area and rate of net photo- synthesis per unit leaf area and increase in fruit or seed number. Therefore, when the N or P sup- ply is insufficient, low rates of photosynthesis or insufficient expansion of epidermal cells (MacAdam et al. 1989, Marschner 1995) can lim- it leaf growth rate. This effect varies among plant species and there is also a diurnal component. In monocotyledons, cell expansion is inhibited to the same extent during the day and night, whereas in dicotyledons the inhibition is more severe in the daytime (Radin 1983). Mineral nutrition can influence the mineral composition of the plant in addition to affecting the yield response. The effect of N fertilization on mineral composition of forage grasses has been studied widely (Rinne et al. 1974a, Rinne et al. 1974b). N had an effect on other elements, increasing clearly concentrations of K, Ca (Rinne et al. 1974a, Kätterer et al. 1998), Mg, Na, and Zn (Rinne et al. 1974a, Rinne et al. 1974b, Hop- kins et al. 1994), but decreasing those of P (Rinne et al. 1974a, Kätterer et al. 1998), Fe, Mo and 26 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Zn (Rinne et al. 1974b, Hopkins et al. 1994) and Si (Wallace et al. 1976, Rinne 1977, Wallace 1989) in grass. The changes caused by N fertili- zation were affected by the age of the ley, soil type and cutting time (Rinne et al. 1974b, Rinne 1977). 2.4.3 Choice of cultivar One of the main goals in breeding agrofibre plant cultivars is large DM yield (Lindvall 1992, Mela et al. 1996, Sahramaa and Hömmö 2000a). How- ever, the variation in quantitative traits includ- ing yield capacity depends on several genes, the effects of which are often smaller than the vari- ation arising from environmental factors such as climate, nutrition and management (Baltensperg- er and Kalton 1958, Sachs and Coulman 1983, Østrem 1988a, Falconer and Mackay 1996). There are, of course, traits with a strong genetic component, such as the number of panicles and stems, and the height of the plant that impact on DM yield and quality (Baltensperger and Kalton 1958, Bonin and Goplen 1966, Berg 1980, Østrem 1988b, Sjödin 1991, Lindvall 1992). For production of grass fibre, early maturing varie- ties are preferred, as late ones tend to have a higher leaf to stem ratio (Berg 1980). Fibre length is another important quality trait, and Robson and Hague (1993) reported differences among varieties in fibre length. Genetic varia- tion in lignification among the ecotypes of fes- cue and maize genotypes has also been reported (Gaudillere and Monties 1989). Significant dif- ferences in lignin content and its monomeric composition were found between upper and low- er internodes of maize (Gaudillere and Monties 1989, Monties 1990). Alkaloids found in some grasses are harmful for livestock in feeds, but they may be even beneficial in fibre production because they resist the attack of harmful insects or herbivores (Coulman et al. 1977). Variation in concentration of alkaloids is genetically de- termined, but environmental factors, including management, have an impact on alkaloid levels (Østrem 1987, Akin et al. 1990). Low mineral content is a desired quality for raw material for pulp and paper production. Breeding programmes for fibre crops take this into consideration (Lindvall 1997, Sahramaa and Hömmö 2000a) with emphasis on low Si, K and heavy metal concentrations. Jørgensen (1997) reported considerable variation in N and K con- tents of different Miscanthus populations collect- ed from Japan. Mineral concentrations in the spring harvest were related to degree of crop senescence in autumn. The first severe frost in the autumn increased the rate of mineral loss from plant material. Jørgensen (1997) suggest- ed that there are good prospects for future de- velopment of plant material with low mineral contents because of the significant within-spe- cies variation in relation to the time of senes- cence, yield and mineral content. 2.5 Pulping of field crops Pulping for papermaking is a process of deligni- fication, whereby lignin is chemically dissolved permitting the separation of fibres in the raw material. ‘Paper pulp’ is actually an aggregation of the cellulosic fibres that are liberated from the plant material (Biermann 1993). The fibres in the raw material are separated by treatments with alkali, sulphite or organic solvents, which partly remove the lignin and other non-cellulose components from the matrix. Fibres can also be separated in mechanical or chemi-mechanical pulping processes. After the fibres have been removed from the aqueous suspension they are washed and bleached. For the final papermak- ing process a water suspension of different fibre components and additives is pressed and dried on a fine screen running at high speed, and formed into a thin paper sheet. This procedure makes the fibres bond together and form a lay- ered network. The inter-fibre bonding is impor- tant in determining the strength of the paper (Wood 1981, Philip 1992). The choice of different types of pulps de- pends on the quality desired in the end product. 27 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. In fine papers the amount of short fibre (fibre length 0.6–1.9 mm) is 20–100% (Atchison 1987b). Long fibres from softwoods (coniferous trees) or non-wood plants (flax, hemp, kenaf) are necessary to form a matrix of sufficient strength in the paper sheet. The shorter hardwood fibres (deciduous trees, grass fibres) (Hurter 1988) contribute to the properties of pulp blends; es- pecially opacity, printability and stiffness are improved. The role of the short fibre pulp in fine papers is to give good printability to the paper. On the other hand, the required strength for run- nability is adjusted by adding long softwood fi- bres (Hurter 1988, Paavilainen 1996). In high quality papers such as writing and printing pa- pers, chemical pulps are used. Mechanical and chemi-mechanical pulps are good raw materials for newspapers (Atchison 1987b). One of the main problems in pulping non-wood plants is the high concentration of minerals and especially Si. In alkaline pulping, silica dissolves into the cooking liquor, and when the black liquors are evaporated for recovery, the concentration of SiO 2 increases to such an extent that it may cause problems in the process (Hultholm et al. 1995). Several desilication methods (Judt 1991, Kulkar- ni et al. 1991) have shown that removal of SiO 2 is possible, but they are seldom used in small pulp mills, where most commercial non-wood pulp is produced (Sadawarte 1995). 2.5.1 Pretreatment of the raw material Mechanical treatment of agrofibres Heterogeneity of the biomass can result in vari- ation also in the quality of the pulp when the entire plants are used in pulping (Ilvessalo-Pfäf- fli 1995). In the pulp mill, however, leaves, dust and dirt can be removed by air fractionation be- fore cooking. Mechanical pretreatment improves the quality by increasing the bleachability of the pulp, and decreasing the silica and other useless particles present in the raw material. SiO 2 can be decreased by 40% through a pretreatment of the grass (Paavilainen et al. 1996b). A dry frac- tionation system developed in Sweden includes shredding, chopping, milling in a disc mill and screening of reed canary grass. Fractionating produces a chip fraction of mainly internodes for pulp production and a meal fraction of leaves and sheaths that can be used in bioenergy pro- duction (Finell et al. 1998, Paavilainen et al. 1999). Because of the large quantity of fines (small particles other than fibres) dewatering ability of pure grass pulps is inferior to that of hard wood pulp (Wisur et al. 1993, Paavilainen et al. 1996b). Thus the drainage time in paper- making is longer, but mechanical fractionation and blending of the grass pulp with long-fibred softwood pulp improves the dewatering and dry- ing properties (Paavilainen et al. 1996a, Paavi- lainen et al. 1996b). Biotechnical and enzymatic pretreatments of agrofibres Besides the mechanical fractionation, decreasing the fines is possible by treating the biomass with white rot fungi (Phlebia radiata Fr., P. tremellosa, Pleurotus ostreatus Jacq., Ceriporiopsis subver- mispora) in oxygenated bioreactors before chem- ical pulping (Hatakka and Mettälä 1996, Hatakka et al. 1996). The fungi first decompose lignin and later attack the cellulose. White rot fungi seem to break down the parenchyma cells effectively and thus, decrease the amount of fines. When spring- harvested, completely dead reed canary grass was used as a substrate and C. subvermispora as a fun- gal treatment, lignin content decreased from 10.4% to 8.2%, cellulose content increased from 47.2 to 50.4% and pulp yield from 47.1 to 48.% (Hatakka et al. 1996). The possibilities for using enzymatic methods for improving pulping and bleaching of fibres have also been studied (Pere et al. 1996). 2.5.2 Commercial and potential methods for pulping non-woody plants It has been estimated that there are about 40 dif- ferent processes suitable for pulping non-woody 28 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper plants, but only a few of them have been used commercially (Ranua et al. 1977). The most used methods include alkaline processes such as sul- phate (Kraft)- and soda (NaOH)-methods and also sulphite methods (Table 7). The most com- monly used commercial method in pulping non- woody species in countries producing non-wood pulp is still the soda method (Sadawarte 1995). There are also several new methods with good potential to produce high quality pulp from non- woody species (McDougall et al. 1993). Soda method The soda process is a common method for pro- ducing non-wood or straw pulp (Paavilainen et al. 1996b). In the soda process the cooking chem- ical is mainly sodium hydroxide. This process leaves more insoluble carbohydrates in pulp and gives a better pulp yield than Kraft method. However, the strength properties and lignin con- tent are similar in pulps produced with the soda and the Kraft processes (Ranua et al. 1977). The soda process was the basis for the development of the straw pulping industry in Europe (Ranua et al. 1977, Winner et al. 1991). Kraft method The Kraft or the sulphate method is the most fre- quently used process in making chemical paper pulp from wood. In Finland about 90% of all the chemical paper pulp is made using the Kraft process (Paavilainen 1996) and globally it is 80% (Ervasti 1996). The raw material is treated with a highly alkaline solution of NaOH, which is known to cleave lignin, but also eliminates a part of the hemicellulose. The undesirable breakdown of hemicellulose is largely avoided by adding Na 2 S in the solution, and in this way a very high concentration of NaOH can be avoided in the pulping liquor (McDougall et al. 1993). The Kraft process produces papers with increased fibre strength and density and low electrical con- ductivity (McDougall et al. 1993). Sulphite pulping Sulphite pulping involves heating the raw mate- rial in a solution of NaHSO 3 and/or Na 2 SO 3 (Atack et al. 1980, Costantino et al. 1983). Sul- phonates form and are hydrated, and the swell- ing of fibres helps remove further lignin. In del- eterious side reactions, the strongly ionised sul- phonic acids increase the acidity of the pulping medium resulting in condensation reactions be- tween phenolic moieties in lignin, forming in- soluble resin-like polymers, and degradation of the hemicelluloses and amorphous regions of cellulose. This affects both lignin removal and the quality of the fibres (McDougall et al. 1993). Sulphite pulp is, however, still used to produce papers with specific properties such as sanitary and tissue papers, which must be soft, absorbent and moderately strong (McDougall et al. 1993). Phosphate pulping In phosphate pulping the alkaline cooking chem- ical is trisodium phosphate (Na 3 PO 4 ). In pulp- ing of grass plants anthraquinone is used as a catalytic agent and the cooking temperature is set between 145 to 165°C. The properties of pulps prepared with the phosphate and soda methods are similar (Janson et al. 1996a). Pulping with organic solvents Since the 1930s organic solvents, such as alco- hols, in different combinations with sodium hy- droxide or sodium carbonate, have been studied for pulping (Kleinert and Tayenthal 1931). In the IDE-process (Impregnation – Depolymerisation – Extraction) (Backman et al. 1994) the raw material is first impregnated with a mixture of sodium hydroxide and sodium carbonate, and then at the depolymerisation stage, it is subject- ed to ethanol-water solution at a temperature of 140–190°C. At the extraction stage, residual lignin is extracted from the pulp with an aque- ous ethanol solution. In this process the silica problem remains partly unsolved, but the sepa- ration of silica is easier at the impregnation stage than from the black liquor (Hultholm et al. 1995). In the ALCELL process the non-wood raw ma- terial is cooked in an ethanol-water blend. On a pilot scale, pulp yields and quality have been comparable with those of conventional market pulps (Winner et al. 1991). The MILOX pulping 29 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. and bleaching method is based on formic acid and hydrogen peroxide. In the acid MILOX proc- ess silica remains in the pulp after cooking, but it is possible to dissolve it in alkaline H 2 O 2 from the bleaching process (Seisto and Sundquist 1996). Table 7. Commercial and potential pulping methods for non-woody plants. Process Major pulping chemical Commonness References Soda NaOH Commonly used Paavilainen et al. 1996b Kraft NaOH + Na 2 S Commonly used for wood Paavilainen 1996 Sulphite NaHSO 3 and/or Na 2 SO 3 Commonly used Atack et al. 1980 Phosphate Na 3 PO 4 Potential method Janson et al. 1996 Milox Formic acid " Seisto and Sundquist 1996 IDE NaOH, sodium carbonate, " Backman et al. 1994 ethanol-water blend Alcell Ethanol-water blend " Winner et al. 1991 3 Objectives and strategy of the study The need for producing field crops as raw mate- rial for pulp and paper emerged during the be- ginning of the 1990s when it was estimated that between half and one million hectares of arable land would be set aside from cultivation in Fin- land. Simultaneously, consumption of paper and importation of hardwood for papermaking in- creased. Therefore, the National Agrofibre Pro- gramme in Finland was set out to develop eco- nomically feasible methods for producing spe- cific short-fibre raw material from field crops available in Finland and process it for use in high quality paper production. The program covered the entire processing chain, from raw material production to the end product (Table 8). It pro- ceeded from a literature study and preliminary testing of species, through crop management and post harvesting research, seed production re- search, studies on pretreatment and pulping methods to the pilot processing for pulping, bleaching, paper making and printing which were carried out in 1995, and to the tests in full scale paper mill in 1999. Calculations for the pulp and paper mill were performed during the pro- gramme. A breeding programme for reed canary grass started in 1993 in order to develop a vari- ety for domestic fibre production. The chronol- ogy and strategy for the research process of the National Agrofibre Programme in Finland dur- ing 1990–1999 is described in Table 8. This the- sis covers the results from the crop production experimentation of the Agrofibre Program out- lined above, including selection of the plant spe- cies in preliminary research in 1990, research on crop management methods 1993 to 1999, and variety research from 1996 to 1999. The objectives of this thesis were 1) to eval- uate the results from crop production experi- ments in the Agrofibre Program in order to se- lect plant species for non-wood fibre production, and for short fibre pulping and for the fine pa- per industry in Finland, 2) to develop crop man- agement methods for the selected species and 3) to study possibilities to improve the fibre yield and quality of the selected species through man- agement methods for raw material for pulping, and lastly, 4) to describe an appropriate crop- ping system for large-scale fibre plant produc- 30 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper tion. Finally, 5) through the results of this the- sis, it should be possible to improve our under- standing of how to locate, select and introduce a crop for a new purpose. The first step in this study was to explore the potential and feasibility of cultivating field crops as raw material for pulping. During 1990, data were collected from trials that included 17 can- didate species in order to identify the most po- tentially useful fibre crops. After determining the biomass yield, fibre quality, and mineral com- position of the plant material, reed canary grass, tall fescue, meadow fescue, spring barley, goat’s rue, red clover and lucerne were selected for the studies in 1991–1993. The selection was carried out based on the mineral and pulping analyses and earlier knowledge and experience on the yielding capacity, adaptability to the Finnish cli- mate conditions, domestic seed production, and low production and harvesting costs. The fac- tors used to select the fibre plants for the subse- quent experiments are presented in Table 9. The studies in 1991 and 1992 focused on yielding capacity and biomass quality at different harvest timings and at different fertilizer application rates of the seven species. Most results from the Table 8. The chronology of the research process of the National Agrofibre Program in Finland since 1990. 31 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. years 1991 and 1992 have been published earli- er (Pahkala et al. 1994, Pahkala 1997) and are therefore not included in this thesis. In 1993, only the two most promising crop species, reed canary grass and tall fescue, were included in the study. In 1995, studies with tall fescue ceased, and reed canary grass was cho- sen as the main crop for the study. The trends in the research strategy for the crop production re- search of the Agrofibre Programme during 1990– 1999 are described in Table 10. The results of three studies are included in this thesis: Table 9. Factors used to select the most potentially useful fibre plant species. Properties of the species. Yes (+), no (–), intermediate (+/–). Plant species High Good Adaptability Domestic Mechanisation Low yield quality seed available production production costs Grasses Reed canary grass + + + + + + Tall fescue +/– + +/– + + + Meadow fescue +/– + + + + + Timothy +/– + + + + + Legumes Red clover + – – + + + Lucerne + – – – + + Goat’s rue + – +/– + + + Fibre crops Linseed straw +/– + +/– + +/– +/– Hemp + + +/– – – – Nettle – – – – – – Cereal straw and oilseed crops Winter rye +/– + + + + + Oats +/– + + + + + Barley +/– + + + + + Wheat +/– + +/– + + + Turnip rape +/– +/– + + + + Rape +/– +/– +/– + + + Common reed + + – – – +1) 1) harvest costs I Selection of the plant species for non wood fibre production, carried out in 1990, II Study of possibilities through management methods to improve the biomass yield and qual- ity of reed canary grass and tall fescue as raw material for paper making, carried out from 1993 to 1999, and III Study of variation in yielding capacity and quality of commercial reed canary grass culti- vars grown for pulping, carried out from 1996 to 1999. 32 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper T ab le 1 0. S eq ue nc e of th e cr op p ro du ct io n re se ar ch in th e N at io na l A gr of ib re P ro gr am , 1 99 0– 19 99 . R C G = r ee d ca na ry g ra ss . T he e xp er im en ts in cl ud ed in th is th es is a re pr in te d in b ol df ac e. 33 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 4.1 Establishment and management of field experiments Field experiments were established using a plot seed drill or combine drill. The plot size in the experiments sown using the plot seed drill (Øy- jord plot drill, F.Walter and Wintersteiger, Aus- tria) was 1.5 m x 10 m with a net plot width of 1.25 m. Before sowing, the experiments were dressed with the NPK compound fertilizer at 70– 14–28 kg ha-1. When the crop was sown using combine drilling (Tume 2000, Nokka-Tume Oy, Finland), with a basal dressing of NPK at 70– 14–28 kg ha-1, the plot size was 2–3 m x 10 m and the harvested area 1.5 x 10 m. The plots were oriented across the sowing lines in the field. The sowing rate was 800 to 1000 viable seeds m-2 and the sowing depth 1–2 cm. In all experiments, fertilizer was broadcast using a manual Tume plot fertilizer spreader (Nokka-Tume Oy, Fin- land) in the spring after delayed harvest and be- fore the new growth had started. Herbicide was used (Basagran MCPA, a mixture of bentazone and MCPA with active ingredient of 0.75 kg and 0.375 kg ha-1, respectively) against dicotyledo- nous weeds and was applied when the crop had two to four leaves and weeds had emerged. The plots were harvested using a Haldrup forage har- vester (J. Haldrup A/S, Denmark) during the growing season or at delayed harvest in the spring. Delayed harvest was carried out in late April or in May, when the snow and ice had melted and the soil had dried enough to support a harvester. 4.2 Sampling For determination of the DM, crude fibre and mineral content, two samples of 200 g (100 g for spring harvested material) were dried at first for two hours at 105°C and then 17 hours at 60°C. To analyse the different plant fractions, a sample of 25 x 50 cm (consisting about 80–120 plants) was taken from each plot, cutting the plants near the soil surface. The dried grass sam- ples were separated into stems, leaf blades, leaf sheaths and panicles. The weight of the plant parts was determined after drying the samples for 17 hours at 60°C. The fresh weight of weeds in harvested biomass was determined from a sample of 500 g. 4.3 Measuring chemical composition of the plant material For the determination of crude fibre, the dried plants or stems, leaf sheaths and leaf blade frac- tions of the samples were milled to less than 1 mm diameter. The crude fibre was measured us- ing a modified AOAC method (AOAC 1980) with Fibertec system M (Tecator, Sweden), which consists of hot (1020 Hot Extractor) and cold (1021 Cold Extractor) extraction units. The sample was boiled first in dilute acid (H 2 SO 4 ) and then in dilute alkali (KOH). The residue, not soluble in the acid-alkali treatment, was meas- ured gravimetrically and the results were given as percentage of DM in total biomass. Mineral composition was analysed after dry- ing. The samples were milled to less than 1 mm in diameter. The concentrations of K, Fe, Mn and Cu were measured using a flame AAS (Perkin Elmer 200 Flame Atomic Absorption Spectrom- eter, Perkin Elmer Corporation, USA), the con- centration of silica (SiO 2 ) and ash by gravime- try, in both cases after dry ashing at 500°C. Ni- trogen content was determined using the Kjel- dahl method (Tecator 1981) with Kjeltec Auto 1030 Analyzer (Tecator, Sweden) and P by spec- trophotometry (Shimadzu UV-160A, Shimadzu Corporation, Japan). In the comparison of reed 4 Materials and methods 34 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper canary grass cultivars, Si and K were determined by ICP (inductively coupled plasma spectrome- try) (Thermo Jarrell Ash Irish Advantage, Ther- mo Jarrel Ash Corporation, USA) (Huang and Schulte 1985) after microwave digestion. The plant samples were digested in a mixture of con- centrated HNO 3 , HF and 30% H 2 SO 4 . A two step, 15 min, digestion program was used and the sample was diluted with a boron solution before ICP measurement (Fridlund et al. 1994). Chemical analyses were performed at the Chem- istry Laboratory of MTT. 4.4 Pulp and paper technical measurements For evaluation of the plant material in 1990, dried biomass samples of 800 g for each of the 17 plant species were cooked for 10 minutes in NaOH (16% of DM) with anthraquinone (0.1% of DM) at 165°C with time of rise 60 min, using 15-litre electrically heated rotating digesters. The screened pulp yield, the uncooked screenings, the viscosity, the fibre length and the kappa number were determined after cooking and com- pared with the corresponding values for wood chips, the commercial raw material for pulp mills. In the comparison of plant fractions of reed canary grass, the sulphate pulping experiments were conducted in 1-litre air-heated autoclaves, where 100 g of plant material was cooked for 10 minutes at 165°C in NaOH solution. The cook- ing conditions were as follows: heating to 165°C within 30 min, liquor-to-raw material ratio 5 l kg-1 oven dried grass material and the charge of effective alkali 4.5 mol kg-1 (18% NaOH), sul- phidity 38%. After cooking, the pulps were carefully washed with deionized water, disintegrated in a laboratory mixer for 30 seconds and screened on a flat screen (0.25 mm slots). The pulps were collected on a wire cloth. To avoid loss of fine material in the screening procedure, the filtrate was used as dilution water in screening (closed cycle screening). Total pulp yield (% of DM), amount of screenings (% of DM), kappa number (ISO 302, indicates the lignin content in the pulp, in birch pulp usually about 15–20) and black liq- uor pH were determined. Brightness (%) was determined as an average of the values meas- ured from both sides of a laboratory sheet. Fibre properties of the pulps (fibre length, coarseness and weight) were measured with Kajaani FS 200 Fiber Analyzer (Kajaani Electronics, Finland). The pulping characteristics were determined at KCL. 4.5 Methods used in individual experiments 4.5.1 Selection of plant species In 1990, data were collected from several field trials including 16 field crops and one wild spe- cies (common reed) to determine the fibre and mineral composition of the plants (Table 11). The properties of non-wood species were compared with those of birch. Grasses were harvested at the silage stage (when about 20–80% of pani- cles or ears had emerged) in June, or at the seed ripening stage, except for the second cut of reed canary grass that was done at the panicle emer- gence stage. Lucerne, goat’s rue and red clover were harvested at the full flowering or seed rip- ening stage. Straw of cereals, linseed, rape, tur- nip rape and fibre hemp were harvested at the seed maturity stage in September. The samples were dried and chopped into 3 to 5 cm sections with a Skiold straw chopper (Skiold A/S, Den- mark). For analysing the mineral and fibre content, the samples from the field trials were taken as a mixture from two to four replicates, except for birch, common reed and nettle (Urtica dioica L), which derived from only one sample. 35 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 4.5.2 Crop management research The field experiments concerning research into crop management of reed canary grass and tall fescue were conducted in Jokioinen (60°49’N, 23°28’E) and Vihti (60°21’N, 24°24’E). Soil types, sowing dates and methods, and harvest years for the experiments included are present- ed in Table 12. Experiments for harvest timing, row spacing and fertilizer use The field experiments for reed canary grass and tall fescue were set up as nested designs, where the main plot factor was harvest timing with three harvests (June+Oct, Aug, May), the subplot fac- tor was row spacing (12.5 and 25 cm) and the sub-sub-plot factor was fertilizer level (N rate at 0, 50, 100, 150 kg ha-1) (Table 13). The exper- iments were sown with a plot seed drill in 1993 on sandy clay soil in Jokioinen and on organic soil in Vihti. The first harvest (a1) was carried out when more than half of the panicles were flowering. The regrowth biomass was harvested in Octo- ber. The total yield (June+Oct) was considered a sum of those two harvests. The second harvest (a2) was adjusted so that seed was fully ripened but not yet shattered. Delayed harvest (a3) was carried out in the following year in May when the soil was dry enough to support a harvester. Sowing rate was 800 seeds m-2 with 12.5 cm row space (b1), and 400 seeds m -2 in the case of a 25 cm row space (b2). The reed canary grass trials Table 11. Plant species, their origin and growth stage in the preliminary screening. Trivial name Latin name Origin of Growth stage the samples Location at harvest Reed canary grass Phalaris arundinacea L. Tuusula 60°25’N, 25°01’E Culms 40 cm " " " " Panicles emerged Tall fescue Festuca arundinacea Schr. Viikki 60°13’N, 25°02’E 20% panicles emerged " " " " Seed ripening Meadow fescue Festuca pratensis Huds. Viikki " 80% panicles emerged " " " " Seed ripening Timothy Phleum pratense L. Jokioinen 60°49’N, 23°28’E 40% ears emerged " " " " Seed ripening Common reed Phragmites communis Trin. Vehmaa 60°35’N, 21°46’E Anthesis " " " " Senescence Winter rye, straw Secale cereale L. Jokioinen 60°49’N, 23°28’E Seed ripened Oat, straw Avena sativa L. " " Seed ripened Spring barley straw Hordeum vulgare L. " " Seed ripened Spring wheat straw Triticum aestivum L. " " Seed ripened Goat’s rue Galega orientalis L. Viikki 60°13’N, 25°02’E Anthesis " " " " Seed ripening Red clover Trifolium pratense L. Jokioinen 60°49’N, 23°28’E Anthesis " " " " Seed ripening Lucerne Medicago sativa L. " " Anthesis " " " " Seed ripening Linseed, stem Linum usitatissimum L. " " Seed ripened Fibre hemp, stem Cannabis sativa L. " " Seed ripened Nettle Urtica dioica L. Mikkeli 61°41’N, 27°18’E Anthesis Spring turnip rape Brassica rapa L. Jokioinen 60°49’N, 23°28’E Seed ripened Spring rape Brassica napus L. " " Seed ripened Birch, chipped Betula spp. L. Commercial raw material 36 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper were harvested in 1994, 1995, 1996 and in spring 1997. The tall fescue trials were harvested in 1994, 1995 and in spring 1996. Experiment on age of the reed canary grass ley The effect of the age of the ley on the total DM yield, proportion of plant fractions and mineral and fibre content of reed canary grass was stud- ied in a field experiment established in 1990 on sandy clay soil in Jokioinen. The plot size was 15 m2. DM yield was measured in 1991–1998, the proportion of the plant parts in 1992–1998, mineral and crude fibre content in 1991–1994 and pulping characteristics in 1991–1992. The field experiment for reed canary grass comprised two levels of NPK (26–2–3) fertilizer (100 and 200 kg N ha-1) that were completely randomised into blocks. The fertilizer treatments were com- bined with two harvest times in a split-plot de- sign with 3 replicates. The harvest dates from autumn 1991 to spring 1999 are presented in Table 14. Data on DM and stem yields (kg ha-1) were recorded at both harvests. Experiment on sowing time and cover crop of reed canary grass The reed canary grass sowing time trial was laid out in Jokioinen in 1995 on sandy clay soil as a randomised block design with four replicates. The sowing rate for reed canary grass (cv. Pala- ton) was 800 seeds m -2 and the plot size was 1.5 x 9 m. The sowing times were 1) May 30th, 2) June 22nd, 3) July 21st, 4) August 22nd, 5) Sep- tember 22nd. Total DM and stem yields (kg ha-1) Table 12. Experiments on crop management of reed canary grass and tall fescue. Sowing method “Plot” = plot seed drill, “Field” = combine seed/fertilizer drill Sowing Crop species Site Soil type Sowing time method Variety Harvest years Experiments on harvest timing, row spacing and fertilizer use Tall fescue Jokioinen sandy clay 12.5.1993 Plot Retu 1994–95 Vihti organic soil 5.5.1993 Plot Retu 1994–95 Reed canary grass Jokioinen sandy clay 12.5.1993 Plot Venture 1994–96 Vihti organic soil 5.5.1993 Plot Venture 1994–96 Experiment on age of the reed canary grass ley Reed canary grass Jokioinen sandy clay 23.7.1990 Field Venture 1991–99 Experiment on sowing time and cover crop of reed canary grass Reed canary grass Jokioinen sandy clay 30.5–20.9.1995 Plot Palaton 1996–99 Experiment on timing the delayed harvesting Reed canary grass Jokioinen sandy clay 25.5.1992 Field Venture 1994–98 Table 13. Design for the experiments on harvest timing, row spacing and fertilizer application rate for reed canary grass and tall fescue in Jokioinen and Vihti. Main plot, Sub-plot, Sub-sub-plot, harvest row spacing fertilizer rate kg ha-1 N P K a1 at flowering stage June, 2nd cut October b1 12.5 cm (800 seeds m-2) c1 0 0 0 a2 at seed ripening stage in August b2 25.0 cm (400 seeds m-2) c2 50 4 6 a3 delayed harvest in spring in May c3 100 8 12 c4 150 12 18 37 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. were obtained at spring harvests in 1997, 1998 and 1999. The effect of cover crop was studied in the same trial. Reed canary grass was sown on 30th May either as a pure stand or using barley (cv. Arve) as the cover crop. The sowing rate for barley was 350 seeds m -2. The cover crop was removed 1) as silage on August 28th using a grass harvester (Haldrup) or 2) by threshing on Sep- tember 5th using a plot harvester (Wintersteiger, Austria). The stubble height in both cases was approximately 15 cm. Barley yield was not meas- ured. Total DM and stem yields (kg ha -1) were obtained at spring harvests in 1997, 1998 and 1999. Experiment on timing the delayed harvest Timing of delayed harvest of reed canary grass was studied in spring using two different stub- ble heights, 5 cm and 10 cm, on a farm-scale field. The field for the timing of spring harvest was sown using 1000 viable seeds m -2 (cv. Ven- ture) as a pure stand in spring 1992. The exper- iment was harvested on the same field in five successive years (1994–1998). The first harvest- ing was performed as early as possible when the soil was trafficable. The following three harvests were performed in successive weeks. The plots were fertilized after harvesting on the same day with NPK fertilizer (26–2–3) at the rate of 80 kg N ha-1. The plot size was 15 m2. The experimen- tal design for the study was a split-plot arrange- ment with two stubble heights as main plots and four harvest times as subplots (Table 15). DM content (%) and DM yield (kg ha-1) of the harvested biomass were determined separate- ly for each plot. The length of green shoots (cm) and the height of the harvestable stand (cm) were measured before each harvest. The height of the growing stand and the number of culms m -2 were measured at the end of September. The straw content (% of DM) and the amount of green matter in the biomass (% of DM) were deter- mined from a sample taken from an area of 25 x 50 cm in each plot in September and in May. 4.5.3 Reed canary grass variety trials The experiments for studying the genetic varia- tion of reed canary grass were conducted in 1993 at seven research sites (Table 16). Ten cultivars and breeding lines of reed canary grass were in- Table 14. The harvest dates (from 1991 to spring 1999) of a reed canary grass crop established in 1990 in Jokioinen. Harvest dates Harvest year Autumn Spring 1 16 Sep 1991 5 May 1992 2 24 Jul 1992 27 April 1993 3 29 Jul 1993 25 April 1994 4 3 Aug 1994 11 May 1995 5 25 Jul 1995 8 May 1996 6 16 Aug 1996 12 May 1997 7 16 Aug 1997 11 May 1998 8 12 Aug 1998 5 May 1999 Table 15. The design of the experiment for timing of delayed harvest. Dates for each harvest are given separately for each year. Main plot, Sub-plot, stubble height harvest Harvest dates yearly 1994 1995 1996 1997 1998 a1 5 cm b1 5 May 3 May 9 May 6 May 11 May a2 10 cm b2 12 May 10 May 17 May 13 May 18 May b3 19 May 17 May 23 May 20 May 26 May b4 26 May 26 May 30 May 27 May 2 June 38 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper cluded in variety trials. The cultivars and breed- ers were as follows: Cultivar Breeder R-90-7587 Land O’Lakes, USA Palaton Land O’Lakes, USA Vantage Iowa Agricultural Experiment Station, USA Rival University of Manitoba, Canada Jo 0510 MTT, Jokioinen, Finland Motterwitzer DSG-Berlin, Germany Barphal 050 Barenbrug, the Netherlands Venture Land O’Lakes, USA Lara Löken Agricultural Research Station, Norway VåSr 8401 Vågønes, Norway The trials were established without cover crop in May or early June 1993 using a plot seed drill. Soil type and nutrition level of the trials is given in Table 17. The first harvest was in au- tumn 1994 at the seed ripening stage. In 1995, only half of the plots were harvested in autumn, the remaining areas (6 to 7 m2) of the plots were harvested in spring 1996, 1997, 1998 and 1999. In this study DM yield (kg ha-1) was recorded only at spring harvest. The mineral and fibre composition of differ- ent plant parts was studied in three cultivars (Pal- aton, Venture, and Lara) harvested in Jokioinen, Ylistaro and Ruukki in spring 1997 from three- year-old leys. For the plant part analysis, sam- ples of 25 x 50 cm were separated into stems, leaf blades, leaf sheaths and panicles. Pulping characteristics and crude fibre of plant parts of the cultivar Palaton from the same location were studied in spring 1998. Table 17. Soil type and nutrition level in the reed canary grass variety trials. Site Soil type pH Electrical Ca K Mg P Clay Humus conductivity mg/l mg/l mg/l mg/l % % siemens m-1 Jokioinen sandy clay 5.43 0.47 1018 180.0 280 7.4 29.4 4.2 Laukaa silty clay 5.50 – 1110 68.0 147 6.0 – – Ylistaro organic soil 5.31 0.82 1431 71.0 142 5.2 19.3 13.4 Tohmajärvi sandy loam 5.70 0.80 1830 46.3 159 5.2 – – Ruukki loamy sand 5.72 0.93 1213 108.0 113 21.5 7.3 6.8 Sotkamo organic soil 5.40 1.52 1692 80.0 180 5.4 12.8 20.3 Rovaniemi loamy sand 6.20 – 1860 238.0 603 20.0 rich in humus Table 16. Locations, harvest dates and cultivars for reed canary grass variety trials. Cultivars: 1 R-90-7587, 2 Palaton, 3 Vantage, 4 Rival, 5 Jo 0510, 6 Motterwitzer, 7 Barphal 050, 8 Venture, 9 Lara, 10 VåSr 8401. Harvest dates Cultivars Site Location 1996 1997 1998 1999 included Jokioinen 60°49’N,23°28’E 20 May 16 May 19 May 19 May 1–10 Laukaa 62°25’N,26°15’E 13 May 11 May 13 May – 1–10 Tohmajärvi 62°11’N,30°23’E 22 May – – – 1–4, 6–10 Ylistaro 62°57’N,22°31’E 26 April 16 May 25 May – 1–4, 6–10 Ruukki 64°42’N,25°00’E 20 May 20 May 20 May 5 May 1–10 Sotkamo 64°60’N,28°20’E 16 May 22 May 22 May 12 May 1–4, 6–10 Rovaniemi 66°34’N,26°10’E 27 May 25 May 11 May – 1–10 39 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 4.6 Statistical methods Results of the field experiment were analysed using PROC MIXED of SAS Statistical Software (Littell et al. 1996) for Windows 6.12. All exper- imental designs, randomisations and statistical analyses, except those for repeated measurements, were performed according to Gomez and Gomez (1984). Statistical analyses with repeated meas- urements were performed according to Gumpertz and Brownie (1993). The covariance structure in the repeated measurements was chosen after com- paring the structures using Akaike’s information criterion (Wolfinger 1996). Assumptions of mod- els were checked by graphical methods; box-plot for normality of errors and plots of residuals for constancy of error variance (Neter et al. 1996) or using PROC UNIVARIATE of SAS. The param- eters of the models were estimated by the restrict- ed maximum likelihood (REML) method. For comparing the fixed effects the CONTRAST statement of PROC MIXED was used to produce t-type contrasts. These data are not shown but are discussed in connection with the results. Experiments for harvest timing, row spacing and fertilizer use The field experiments for reed canary grass and tall fescue were set up in a split-split-plot de- sign in Jokioinen and in strip-split-plot design in Vihti. Results were analysed using correspond- ing mixed models. DM yield, number and pro- portion of stems, DM content, crude fibre, ash, SiO 2 , N, P and K content were analysed sepa- rately for each year on clay (Jokioinen) and on organic (Vihti) soil, for both species, to test dif- ferences among harvest timings, row spacing and fertilizer application levels and their interactions. In 1995, the DM yield data for reed canary grass for Jokioinen and the data for DM content of tall fescue for Vihti were logarithmically trans- formed to give homogeneity of variance and normal distribution. The significant yield differ- ences caused by harvest timing, row spacing and fertilizer rate were examined using the contrast statement in PROC MIXED. Experiment on age of the reed canary grass ley The field experiment comprised two fertilizer application rates that were completely ran- domised into blocks. Commercial NPK fertiliz- er was used. The fertilizer treatments were com- bined with two harvest timings in a split-plot design with 3 replicates. To establish differenc- es, analysis of variance was done for DM yield, stem proportion and number of stems m-2, con- tent of crude fibre, ash and silica as well as for pulping characteristics. Harvest year was used as a repeated factor when analysing the varia- bles. The year of harvest had a correlated effect when used as a repeated factor. After testing dif- ferent possibilities for analysing the DM yield and stem yield the covariance structure chosen was ARH(1). The heterogeneous first-order au- toregressive ARH(1) structure assumes exponen- tially declining correlations (Wolfinger 1996) ac- cepting random variation among the years. The covariance structure chosen for the quality varia- bles was that for compound symmetry (CS) where the covariances in the model remain constant. Experiment on sowing time and cover crop of reed canary grass The five sowing times were completely ran- domised across four blocks. The data for DM yield, DM content, number of stems and propor- tion of stem fraction years were analysed for three years using the mixed procedure. Harvest year was used as a repeated factor when analys- ing the variables. The covariance structure of the repeated measurements best fitted ARH(1). Experiment on timing the delayed harvest The effect of four successive harvests (subplots) of reed canary grass was studied at two cutting heights (main plots) in an experiment designed as a split-plot with four replicates. The five years were used as a repeated factor when analysing the variables DM yield and DM content, and the four years when analysing proportion of stem fraction, number of stems and the variables de- scribing the development of plant stand meas- ured in autumn. The covariance structure of the repeated measurements fitted best was CS. 40 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Reed canary grass variety trials Analysis of variance was done for DM yield at each experimental site separately. Year of har- vest was used as a repeated factor when analys- ing the yield. The covariance structure of the repeated measurements fitted best was UN, which specifies a completely general (unstruc- tured) covariance matrix. The structure does not include any assumptions of equality of varianc- es or relations between covariances, and thus allows variation for each year (Wolfinger 1996). The proportion of plant parts and the mineral content of each plant part was studied in Jokio- inen, Ruukki and Ylistaro from three cultivars. In stem proportion, significant differences among trial sites and varieties were tested using variance analyses. These were also used when testing pulping characteristics among the plant parts for cultivar Palaton. When testing the dif- ferences in mineral (ash, Si, K) and crude fibre content between plant parts from each trial site, the plant part was used as a repeated factor and the covariance structures used were UN or ARH(1). 4.7 Climate data Climate data collected from Jokioinen in 1991– 1999 and from seven research stations are given in Appendix I. The data from the years when the experiments were conducted are compared with the values from 1961–1990 (Finnish Meteoro- logical Institute 1991). 5 Results 5.1 Selecting plant species Mineral composition The concentrations of undesirable minerals were higher in the non-wood species than in birch, and the concentrations in grasses and cereals differed from those in dicotyledons (Table 18). The ash content was lowest in straw of linseed and hemp (3.8–3.9% of DM) and highest in nettle and bar- ley. The silica concentration in grasses ranged between 0.9 and 6.1% of DM and that in dicoty- ledons from 0.2 to 0.8%, being lowest in linseed straw (<0.1%). Plant mineral content was de- pendent on growth stage. Pulping and fibre characteristics Grass biomass and cereal straw were easy and fast to cook taking only 10 to 15 minutes, com- pared with processing wood, which took at least 90 minutes. Only small differences between the monocotyledons were found. Pulp yields were 33 to 40% of DM for grasses harvested during the growth period, and 42 to 48% for cereal straw (Table 19). Pulp yields for dicotyledons were much lower. The amount of screenings, which is insignificant in commercial birch sulphate pulp, was 0.1 to 1.2% for grasses, 11.8% for com- mon reed, 0.6 to 2.6% for cereal straw and 13 to 41% for dicotyledons. Common reed gave a pulp yield nearly as high as cereal straw, but the amount of screenings showed that the cook- ing procedure was not appropriate for reed (Ta- ble 19). Lower kappa numbers indicated that lignin content was lower for grass pulp than for wood pulp. Grasses harvested during the growing pe- riod were easily cooked to kappa number 9 to 14, which was lower than the kappa number for commercial birch sulphate pulp (17–20) (Table 19) and that for the other plants tested. Viscosi- ty of the pulp made of grass, straw or hemp was similar to that of birch pulp. The amount of NaOH (16% of DM) used in trials was too low for dicotyledons. In the case of red clover and goat’s rue the pulp yield, amount of screenings and kappa number, became more acceptable 41 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. when the dose of cooking chemical was in- creased to 20 or 24% of DM (Table 20). 5.2 Effect of crop management on raw material for non-wood pulp 5.2.1 Harvest timing, row spacing and fertilizer use The aim of the study was to establish the combi- nation of harvest timing and fertilizer applica- tion rate that resulted in the highest DM yield of the highest quality. To enhance straw production the doubled row spacing was compared with a 12.5 cm row spacing, which is more commonly used in Finland. Results for each year were ana- lysed separately in reed canary grass and tall fescue. The interaction effects are presented in Tables 21, 24, 26, 29, 32, 36, 39, 41, 44 and 46, and were tested using contrast statements (data not shown in tables). 5.2.1.1 Reed canary grass Dry matter yield Harvest timing and fertilizer application rate af- fected markedly DM yield of reed canary grass, whereas the row spacing had only a minor ef- Table 18. Mineral content in dry matter (DM) of crop samples taken in 1990. Species Growth Ash SiO 2 Fe Mn Cu N stage % % mg kg-1 mg kg-1 mg kg-1 % Monocotyledons Reed canary grass Culms 40 cm 8.76 2.63 56.7 24.0 7.05 1.73 Panicles emerged 8.51 5.61 83.1 50.2 5.40 0.93 Tall fescue 20% panicles emerged 9.54 2.42 101.5 61.9 5.50 2.47 Seed ripening 7.41 2.25 72.8 53.8 3.54 0.90 Meadow fescue 80% panicles emerged 7.62 1.52 100.3 42.4 5.03 1.28 Seed ripening 6.99 2.04 78.8 52.3 4.11 0.97 Timothy 40% ears emerged 5.09 0.88 53.6 38.0 4.42 1.10 Seed ripening 4.17 1.60 130.7 57.3 3.46 0.73 Rye Seed ripened 5.31 3.61 131.3 18.8 3.26 0.52 Oat " 9.10 3.68 159.0 46.2 4.95 0.96 Barley " 10.03 6.13 48.6 15.3 3.29 0.33 Wheat " 5.41 3.52 97.3 13.0 1.76 0.54 Common reed Anthesis 7.79 3.30 51.3 13.4 3.58 1.06 Senescence 4.17 3.82 72.7 13.4 2.78 0.31 Dicotyledons Goat’s rue Anthesis 8.94 0.19 98.7 21.4 10.60 2.87 Seed ripening 6.93 0.27 109.0 17.6 7.95 1.96 Red clover Anthesis 8.24 0.17 90.3 25.3 8.65 2.43 Seed ripening 6.22 0.31 91.2 24.0 7.64 1.83 Lucerne Anthesis 10.33 0.18 125.8 15.8 6.76 2.45 Seed ripening 6.83 0.38 118.5 16.9 7.04 1.89 Linseed straw Seed ripened 3.93 <0.10 54.6 87.3 6.09 0.99 Fibre hemp Seed ripened 3.75 0.19 87.3 11.2 4.05 0.56 Nettle Anthesis 12.13 0.78 100.7 102.7 6.92 2.70 Turnip rape Seed ripened 6.10 0.14 74.5 14.0 3.27 0.96 Rape straw Seed ripened 6.82 0.36 351.2 25.8 3.66 0.83 Birch, chipped 0.41 <0.10 22.3 114.0 0.90 0.11 42 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Table 19. Screened pulp yield (% of dry matter), screenings (% of dry matter), kappa number, viscosity, fibre length (LW) and content of crude fibre (% of dry matter) for crop plant samples taken in 1990 compared to commercial birch sulphate pulp. Pulp process soda-anthraquinone. Plant Growth Pulp Screenings Kappa Viscosity LW Crude species stages yield % % number mm fibre % Monocotyledons Reed canary grass Culms 40 cm 36.9 0.3 9.1 1090 0.57 33.4 Panicles emerged 35.6 1.3 12.1 1220 – 33.8 Tall fescue 20% panicles emerged 32.6 0.1 10.2 910 0.60 27.9 Seed ripening 41.5 0.9 12.6 1070 – 36.8 Meadow fescue 80% panicles emerged 40.1 0.3 12.0 1080 0.72 33.6 Seed ripening 45.5 0.6 13.0 1060 – 40.0 Timothy 40% ears emerged 33.7 1.2 13.5 1020 0.60 28.4 Seed ripening 34.2 2.1 16.6 920 0.62 30.1 Rye Seed ripened 48.2 2.6 12.5 1100 0.90 49.0 Oat Seed ripened 42.3 0.6 14.4 1180 0.80 38.4 Barley Seed ripened 48.3 2.0 19.9 – – 45.7 Wheat Seed ripened 43.4 2.1 10.0 – – 45.3 Common reed Anthesis 38.1 11.8 31.7 – – 43.4 Senescence 48.3 7.6 45.8 – – 45.9 Dicotyledons Goat’s rue Anthesis 16.7 16.9 59.0 810 – 36.3 Seed ripening 13.7 24.2 45.5 790 0.76 41.2 Red clover Anthesis 29.5 6.6 76.8 810 – 27.8 Seed ripening 23.9 13.4 63.4 850 0.70 40.6 Lucerne Anthesis 19.5 11.8 77.3 680 – 30.9 Seed ripening 20.9 17.2 65.0 810 1.08 43.8 Linseed straw Seed ripened 13.0 35.7 80.2 760 – 57.2 Fibre hemp Seed ripened 13.4 41.0 49.2 1100 – 61.4 Nettle Anthesis 9.9 21.5 78.7 610 0.42 33.8 Turnip rape Seed ripened 16.4 36.7 78.9 590 – 56.7 Rape Seed ripened 12.3 38.5 74.7 690 0.83 51.1 Birch Chipped 50.0 – 17–20 >1000 0.90 60.7 Table 20. Pulp yield (% of dry matter), screenings (% of dry matter), kappa number, viscosity and fibre length (LW) for goat’s rue and red clover after pulping at different concentrations of NaOH (% of dry matter). NaOH- NaOH- Pulp Screenings Kappa Viscosity LW Crop species % residue g l-1 % % number mm Goat’s rue 16.0 2.6 13.7 24.2 45.5 790 – " 20.0 6.5 18.3 15.7 38.2 970 1.01 " 24.0 11.7 22.5 11.6 34.7 920 0.92 Red clover 16.0 0 23.9 13.4 63.4 850 0.70 " 20.0 4.7 22.8 9.7 48.5 890 0.87 " 24.0 9.7 24.8 7.7 46.2 930 0.89 43 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Table 22. Effect of fertilizer application rate on total dry matter yield (kg ha-1) of reed canary grass at different harvest timings in 1994, 1995 and 1996 on clay soil in Jokioinen. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June+Oct 6380 7400 8050 9080 7810a Aug 7520 8800 9450 9080 8850a May 5340 6000 6320 6660 6050b *Means for N rate 6380a 7400b 8050c 8450d Means for row spacing* *Means for 12.5 cm 6500a 8080b 8450b 8610b 7910a 25.0 cm 6250a 6720a 7650b 8300c 7230b 1995 June+Oct 3870 4760 4890 5680 4760a Aug 5150 6720 7300 7300 6560b May 5990 7340 7750 8260 7280b *Means for N rate 4930a 6170b 6520b 7000c 1996 June+Oct 6850 7700 9030 9440 8260a Aug 4660 6670 8230 9760 7330b May 5320 7040 8140 8960 7360b *Means for N rate 5610a 7140b 8470c 9390d * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 21. Significance (P values) of difference among harvest time, row spacing and fertilizer application rate in dry matter yield of reed canary grass in 1994, 1995 and 1996 in Jokioinen and Vihti. Jokioinen Vihti Source 1994 1995 1996 1994 1995 1996 Harvest (H) 0.0030 0.0054 0.1170 0.0001 0.0001 0.0001 Row (R) 0.0021 0.1073 0.2277 0.1935 0.9684 0.6792 HR 0.1468 0.3052 0.8931 0.1295 0.4701 0.5114 Fertilizer (F) 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 HF 0.0382 0.4528 0.0043 0.0001 0.0001 0.0001 RF 0.0053 0.1087 0.3554 0.5662 0.0631 0.1162 HRF 0.2681 0.1227 0.4381 0.3927 0.7857 0.0137 fect. In the first harvest year the row effect was pronounced in Jokioinen and in 1996 the har- vest timing x row spacing x fertilizer applica- tion rate interaction was statistically significant in Vihti (Table 21). There were yield variations among years (Tables 22 and 23) caused by dif- ferences in weather conditions (Appendix I). Low precipitation during the growth period of 1995 (Appendix I) resulted in low DM yields, especially on sandy clay soil in Jokioinen (Ta- ble 22). In Vihti, the effect of the drought was recorded as retarded regrowth following harvest- ing in June 1995 (Table 25). On sandy clay soil, the delayed harvest in May 1995 resulted in significantly lower yield when compared with harvest at seed stages (Aug) or earlier summer (June+Oct) in 1994 (Table 22). In 1995, yield at the seed stage did not differ from that of delayed harvest in Jokioinen. In 1996, there were no significant differences in 44 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper DM yields for harvest times on clay soil. The wider row spacing (25 cm) resulted in lower yields in 1994 (Table 22), but subsequently there were no differences in yields attributable to dif- ferent row spacing. Increasing fertilizer use re- sulted in an increase in total yield at the first harvest (June+Oct) of each year. However, the difference in DM yield between crops harvested at the seed stage (Aug) and the delayed harvest (May) at the two highest fertilizer application rates differed only in 1996 (Aug P = 0.0003, May P = 0.0432). On organic soil, row spacing did not effect yield (Table 21) in any of the years or at any harvest times. Harvesting at the seed stage in August gave the highest yield in every year on organic soil (Table 23). Fertilizer application sig- nificantly affected the DM yield, but the effect depended on harvest timing and year. In 1994, increasing fertilizer application rates consistently increased the biomass at both harvest times (June+Oct and Aug) (P<0.01), but when harvest- ed in the following May, only the non-fertilized plots differed from the fertilized plots (P<0.01). In the subsequent years, the fertilizer applica- tion rate had no effect on the biomass yield at delayed harvest May. In 1996, the yield differ- ence attributable to applying100 and 150 kg N ha-1 was not significant in either earlier harvests indicating that 150 kg N ha-1 was unnecessarily high. The plots harvested in June were also cut in October in order to measure the regrowth. Ferti- lizer application rate had the most significant effect on regrowth yield of reed canary grass (Table 24). On clay soil, the regrowth comprised, on average, 17% of the total yield of the plots in 1994, 32% in 1995 and 22% in 1996 and on or- ganic soil 14%, 5% and 28%, respectively (Ta- ble 25). In 1994, the highest rate of fertilizer application increased the regrowth significantly (P<0.001) both on clay and organic soils. In 1995, the regrowth was very restricted in Vihti, being less than 500 kg ha-1, due to low precipi- tation in late summer (Appendix I). In Jokioi- nen, the rainy June in 1995 favoured regrowth. In 1996, increase in the fertilizer application rate decreased the regrowth biomass in plots with 25 cm row spacing in Jokioinen (P<0.001). In Vih- ti, the highest rate increased the regrowth sig- nificantly (P<0.05), but the row spacing had no effect. Table 23. Effect of fertilizer application rates on dry matter yield (kg ha-1) of reed canary grass at different harvest timings in 1994, 1995 and 1996 on organic soil in Vihti. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June+Oct 8730 11450 13030 14320 11880a Aug 9730 11400 12630 13970 11930a May 6580 7910 7730 8330 7640b *Means for N rate 8350a 10260b 11130c 12210d 1995 June+Oct 7150 7800 9290 10480 8340a Aug 6560 12390 13150 14500 12400b May 6110 6140 6650 6000 6220c *Means for N rate 7150a 8780b 9700c 10320d 1996 June+Oct 6020 6990 9320 10260 8150a Aug 7250 11130 14010 14670 11760b May 6130 6140 6120 5970 6090c *Means for N rate 6460a 8090b 9820c 10300c * Means within the column (harvest) and the row (N rate) followed by a different letter are significantly different (P<0.05). 45 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Dry matter content The DM content of reed canary grass was not affected by row spacing in any of the years or at any harvest timings (Table 26). In Jokioinen and Vihti, time of harvest and fertilizer application rate had marked effects on DM content in each of the years studied. Fertilizer rate x harvest tim- ing interaction for DM content was also record- ed. On clay soil, the means of the DM content ranged from 23.9% to 29.9% when harvested in June, from 40.1% to 45.6% in August and from 86.3% to 93.2% in the following May (Table 27). The highest DM contents in June and August were obtained usually at the rate 0 or 50 kg N ha-1 (Table 27). However, in May the effect was no longer registered, and DM percentages var- ied greatly. When grown on organic soil, the DM con- tent of harvested reed canary grass ranged from 17.8% to 31.5% in June, from 31.7% to 42.1% in August and from 72.9% to 89.3% in May (Ta- ble 28). In 1994 and 1995, the highest DM con- Table 24. Significance (P values) of difference between row spacing and fertilizer application rate for regrowth (measured in October) of reed canary grass harvested in June in Jokioinen and in Vihti. Jokioinen Vihti Source 1994 1995 1996 1994 1995 1996 Row spacing (R) 0.2248 0.1693 0.1927 0.2949 0.5427 0.9681 Fertilizer (F) 0.0009 0.2057 0.0006 0.0001 0.0008 0.0693 RF 0.7704 0.5297 0.0001 0.2042 0.7582 0.5390 Table 25. Effect of fertilizer application rate on regrowth (measured in October) of reed canary grass (kg ha-1 dry matter) (harvested in June in 1994, 1995 and 1996 in Jokioinen and in Vihti. Jokioinen Vihti N rate kg ha-1 Means N rate kg ha-1 Means Year Row 0 50 100 150 for year 0 50 100 150 for year 1994 Mean 1250 1200 1320 1510 1320 1470 1600 1720 2090 1720 1995 Mean 1520 1380 1540 1580 1510 270 300 350 430 340 1996 12.5 cm 1830 1810 1950 1910 1790 1590 1510 1960 2250 1830 25.0 cm 1980 1640 1690 1500 Table 26. Significance (P values) of difference in harvest timing, row spacing and fertilizer application rate effect on DM content of reed canary grass in 1994, 1995 and 1996 in Jokioinen and Vihti. Jokioinen Vihti Source 1994 1995 1996 1994 1995 1996 Harvest (H) 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 Row (R) 0.2726 0.6805 0.7799 0.7000 0.1919 0.3795 HR 0.4398 0.6074 0.7111 0.5133 0.0333 0.9530 Fertilizer (F) 0.0001 0.0701 0.0001 0.0024 0.0001 0.1786 HF 0.0001 0.0177 0.0001 0.5131 0.2164 0.0003 RF 0.8846 0.5672 0.7458 0.9828 0.5902 0.8581 HRF 0.1853 0.3884 0.4039 0.9907 0.0537 0.0856 46 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper tents were obtained in biomass harvested from plots that had received 0 or 50 kg N ha-1 (Table 28). The lowest DM contents on organic soil were recorded in biomass harvested from plots that had received the highest amount of fertiliz- er. In 1996, this effect was not recorded. The DM content of regrowth biomass was affected by row spacing only in 1994 in Jokio- inen (Table 29): the plots with wider row spac- ing gave higher DM content. The DM contents of regrowth harvested in October ranged from 33 to 40% on average in Jokioinen, and from 24 Table 27. Fertilizer application rate and row spacing effects on dry matter content (%) of reed canary grass at different harvest timings in 1994, 1995 and 1996 on clay soil in Jokioinen. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June 26.8 25.5 25.4 23.9 25.4a Aug 42.3 42.2 40.9 38.9 41.1b May 87.0 86.3 86.9 87.8 87.0c *Means for N rate 52.1a 51.3b 51.1b 50.2c 1995 June 29.9 30.0 29.1 28.6 29.4a Aug 42.2 45.6 44.6 43.9 44.1b May 93.2 93.0 92.6 93.1 93.0c *Means for N rate 55.1a 56.2b 55.4a 55.2a 1996 June 29.3 29.3 27.2 25.0 27.7a Aug 41.7 43.2 42.4 40.1 41.9b May 89.2 90.5 90.8 90.3 90.2c *Means for N rate 53.4a 54.3b 53.5a 51.8c * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 28. Effect of fertilizer application rate and row spacing on dry matter content (%) of reed canary grass at different harvest timings in 1994, 1995 and 1996 on organic soil in Vihti. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June 30.3 27.6 26.7 26.6 27.8a Aug 39.0 38.5 37.6 37.1 38.0b May 74.5 75.1 73.5 72.9 74.0c *Means for N rate 47.9a 47.1a 45.9ab 45.5b 1995 June 31.5 30.9 29.9 28.9 30.3a Aug 40.8 42.1 40.2 38.7 40.5b May 89.3 88.4 87.9 85.7 87.8c *Means for N rate 53.9a 53.8a 52.7b 51.0c 1996 June 17.8 19.2 18.4 18.2 18.4a Aug 32.2 33.2 34.5 31.7 32.9b May 82.4 80.9 75.3 80.9 79.9c *Means for N rate 44.1a 44.4ab 42.8ac 43.6a * Means within the column or row followed by a different letter are significantly different (P<0.05). 47 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. to 35% in Vihti. These were higher than the re- spective DM percentages in June harvesting on clay soil and in two of the years on organic soil (Tables 30 and 31). Number of stems of reed canary grass In Jokioinen, harvest timing, row spacing and fertilizer application rate had a significant ef- fect on the number of stems m-2 (Table 32). Reed canary grass stands had the highest number of stems in August, averaging 816 m-2 (Table 33). Plants from the plots with 12.5 cm row spacing had more stems and tillers compared with the plots with 25 cm row spacing, when harvested in June (P = 0.0396) and August (P = 0.0011), whereas no significant differences attributable to row spacing were recorded when harvested in May. In June and August, the lowest numbers of s t e m s w e r e f o u n d i n n o n - f e r t i l i z e d p l o t s (P<0.05), whereas in May no differences result- ing from application of different fertilizer rates were established. On organic soil the numbers of stems m-2 were higher than on clay soil. The row spacing used had a modest effect at best on stem number Table 29. Significance (P values) of difference between row spacing and fertilizer application rate effect on DM content of regrowth biomass (measured in October) of reed canary grass in Jokioinen and Vihti in 1994, 1995 and 1996. Jokioinen Vihti Source 1994 1995 1996 1994 1995 1996 Row (R) 0.0343 0.9006 0.7616 0.5320 0.2027 0.5889 Fertilizer (F) 0.6399 0.0775 0.0001 0.0014 0.0106 0.2591 RF 0.7429 0.2523 0.0111 0.8367 0.7017 0.0138 Table 31. Effect of fertilizer application rate and row spacing on dry matter content (%) of regrowth bio- mass (measured in October) of reed canary grass in 1996 in Jokioinen and Vihti. Row N rate kg ha-1 Means for Harvest spacing 0 50 100 150 row spacing 1996 Jokioinen 12.5 cm 33.0 35.3 35.7 36.2 35.0 25.0 cm 34.6 35.3 34.7 36.9 35.3 1996 Vihti 12.5 cm 25.9 24.2 24.4 26.5 25.2 25.0 cm 23.8 27.3 25.4 25.7 25.5 Table 30. Effect of fertilizer application rate on dry matter content (%) of regrowth biomass (measured in October) of reed canary grass in 1994 and 1995 in Jokioinen and Vihti. N rate kg ha-1 Harvest 0 50 100 150 1994 Jokioinen 33.1 33.1 32.6 32.9 1995 Jokioinen 39.3 39.3 40.0 40.1 1994 Vihti 35.4 34.5 33.6 33.7 1995 Vihti 24.7 25.3 25.5 24.6 (Table 35). Harvest timing and fertilizer appli- cation rate affected the number of stems m-2 (P = 0.0526 and P = 0.0301, respectively) (Ta- ble 32). The highest stem numbers per square metre were found in June (1008 stems m-2) and in August (960 stems m-2), whereas at delayed harvest the number of stems was less, 801 stems m-2 (P = 0.0590 Aug, P = 0.0234 June). In June and August the highest number of stems was found in plots fertilized at the highest rate, but in May the lowest rates were associated with the highest stem numbers. 48 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Table 32. Significance (P values) of difference in harvest timing, row spacing and fertilizer application rate effect on number of stems m-2, stem fraction, crude fibre, and mineral content (ash, SiO 2 , N, P, K) of reed canary grass in 1994 in Jokioinen and Vihti. Number Stem Crude Ash SiO 2 N P K Source of stems fraction fibre Jokioinen Harvest (H) 0.0064 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 Row (R) 0.0032 0.0291 0.0067 0.2958 0.8821 0.5950 0.0828 0.6638 HR 0.0192 0.3777 0.0064 0.3752 0.5304 0.2159 0.0466 0.8398 Fertilizer (F) 0.0003 0.0001 0.5249 0.0001 0.0001 0.0001 0.0001 0.0001 HF 0.0408 0.1120 0.0164 0.0813 0.5439 0.0001 0.0106 0.0001 RF 0.6276 0.6141 0.3366 0.3309 0.3253 0.0723 0.4141 0.9235 HRF 0.1232 0.9329 0.3022 0.3575 0.1426 0.7666 0.0206 0.9681 Vihti Harvest (H) 0.0526 0.0002 0.0001 0.0001 0.0002 0.0001 0.0001 0.0001 Row (R) 0.0879 0.5307 0.8140 0.4839 0.5136 0.1301 0.1288 0.6682 HR 0.1789 0.6002 0.3466 0.5378 0.1604 0.9611 0.1337 0.0445 Fertilizer (F) 0.0301 0.0060 0.0365 0.0034 0.0001 0.0001 0.0001 0.0001 HF 0.0133 0.1618 0.4681 0.0001 0.8418 0.0001 0.0044 0.0001 RF 0.7918 0.2684 0.7616 0.1775 0.2819 0.7649 0.9258 0.7968 HRF 0.8720 0.1730 0.4921 0.1209 0.5262 0.3137 0.1612 0.7287 Table 33. Effect of fertilizer application rate and row spacing on number of stems m-2, stem fraction (% of dry matter) and crude fibre of reed canary grass in June and August, 1994 and in May, 1995 on clay soil in Jokioinen. Row spacing 12.5 cm Row spacing 25.0 cm N rate kg ha-1 N rate kg ha-1 Means for Harvest 0 50 100 150 Mean 0 50 100 150 Mean harvest* Number of stems m-2 June 546 656 796 706 676 562 410 746 552 568 622a Aug 814 914 998 969 969 576 732 706 816 708 816b May 572 578 608 500 565 488 596 580 644 577 571a *Means for row spacing 721a 615b *Means for N rate 593a 648a 739b 698a Stem fraction % of DM June 48.0 48.8 45.3 44.6 46.7 46.5 46.5 44.5 43.1 45.2 45.8a Aug 54.7 54.4 52.9 52.3 53.6 54.1 54.5 52.5 52.4 53.4 53.5b May 64.5 63.9 62.8 64.1 63.8 61.5 63.9 61.3 62.7 62.4 63.1c *Means for row spacing 54.6a 53.6b *Means for N rate 54.9a 55.2a 53.2b 53.2b Crude fibre % of DM June 37.6 39.3 39.3 38.3 38.6 38.7 38.7 39.3 38.5 38.8a 38.7a Aug 37.4 36.5 36.1 37.0 36.7 39.2 38.5 38.8 37.9 38.6a 37.7b May 45.6 46.7 45.8 45.8 46.0 45.5 45.9 46.1 46.4 46.0b 46.0c *Means for row spacing 40.4a 41.1b *Means for N rate 40.7a 40.9a 40.9a 40.6a * Means within the column or row followed by a different letter are significantly different (P<0.05). 49 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Stem proportion of reed canary grass In both trials harvest timing and fertilizer appli- cation rate affected the proportion of stems in harvested biomass of reed canary grass (Table 32); the later the harvest, the higher the stem proportion in biomass (Tables 33 and 35). The highest stem proportion was recorded from plots that received the two lowest fertilizer applica- tion rates. Increasing fertilizer application de- creased the relative amount of stem fraction in both trials. In Jokioinen (Table 33), the wider row spacing of 25 cm decreased the stem pro- portion compared with 12.5 cm (P = 0.0291), whereas in Vihti (Table 32), row spacing had no significant effect on stem proportion in harvest- ed yield. Crude fibre content of reed canary grass In both reed canary grass trials (Table 33 and Table 35), crude fibre content of biomass was significantly higher at delayed harvest than when harvested in June or August (P = 0.0001). When biomass was harvested in May, fertilizer appli- cation rate had no significant effect on crude fi- bre content either on clay or organic soil. On clay soil, at the flowering stage, the highest crude fi- bre contents were obtained at 50 and 100 kg N ha-1, and at the seed stage in non-fertilized plots (P<0.05). On organic soil, the fertilizer had very little influence on crude fibre content. However, when harvested at the seed stage, the highest rate resulted in the lowest crude fibre content (P<0.05). Row spacing affected crude fibre con- tent only on clay soil when harvested at the seed stage, being higher at a row spacing of 25 cm (P = 0.0004) than at 12.5 cm. Ash content of reed canary grass Ash content of harvested biomass was, on aver- age, lower on organic soil than on clay soil. In both Jokioinen and Vihti, the ash content of reed canary grass harvested in May (5.7% and 5.1%, respectively) was significantly lower than in plants harvested in August (8.3% and 7.5%, re- spectively) and June (8.7% and 7.8%, respec- tively) (Tables 34 and 35), but row spacing had no significant effect. At all harvests in Jokioin- en and at spring harvest in Vihti, the highest ash contents were found in plants from non-fertilized plots. Silica content of reed canary grass Silica (SiO 2 ) content was lower in plants har- vested on organic soil than from clay soil. At flowering, silica content on organic soil was 2.6% and on clay soil 3.0%, at the seed stage 2.7% and 3.5% respectively, and at delayed har- vest 4.3% and 4.8%, respectively (Tables 35 and 34). Silica contents were strongly affected by harvest timing and fertilizer application rate for both soils (P<0.001), but row spacing had no sig- nificant effect on silica content of harvested bi- omass. Harvesting during the growing period resulted in significantly lower silica contents (P<0.001) than harvesting in May. Silica con- tent was highest in non-fertilized plots and it decreased significantly (P<0.001) when fertilizer application rate was increased up to 100 kg N ha-1. The decrease in silica content was smaller when the fertilizer rates were increased from 100 to 150 kg N ha-1 (P = 0.0121 on clay soil, P = 0.087 on organic soil). Nitrogen, phosphorus and potassium content of reed canary grass Harvest timing and fertilizer application rate had a significant effect (P<0.001) on N, P and K con- tent of reed canary grass on both clay and or- ganic soils (Tables 32, 34 and 35). The content of these minerals was lower the later the grass was harvested. The higher fertilizer application rates increased the N content of plants signifi- cantly in both trials at all harvests (Tables 34 and 35). However, at delayed harvesting the dif- ference resulting from the application rates of 100 and 150 kg N ha-1 was not significant in ei- ther of the trials. The rates of 100 and 150 kg N ha-1 increased the P content in plants significantly on organic soil at all harvest times (Table 35). The effect of fertilizer was not as clear on clay soil: only 150 kg N ha-1 seemed to increase the P content in plants compared with other fertilizer application rates. On clay soil, the wider row spacing resulted in lower P content at both sum- 50 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper mer harvests and the difference attributable to the row spacing was significant (P = 0.0104) solely at the seed stage (Table 34). During the winter, the K content decreased from about 21 to 1.6 g kg-1 DM in both trials. All the fertilizer application rates increased the K content in plants significantly (P<0.01) on clay soil at harvests in June and August (Table 34). On organic soil, 150 kg N ha-1 did not result in increased K content compared with 100 kg N ha-1 at summer harvests. At delayed harvest, increas- ing fertilizer applications were not associated with altered K content of the biomass. 5.2.1.2 Tall fescue Dry matter yield On both clay (Jokioinen) and organic (Vihti) soil, harvest timing and fertilizer application rate had significant effect (P<0.01) on DM yield of tall fescue in 1994 and 1995, whereas row spacing had no marked effect (Table 36). In 1994, the first harvest in June, followed by an additional harvest in October, gave the highest total DM yield on both soil types. In 1995, the highest yields were obtained when the crop was harvest- ed at the seed stage in August. Delayed harvest in May resulted in significantly less yield than harvest at the seed stage in both years and in both trials (in 1994 P<0.001, in 1995 P<0.03). The yield from delayed harvest of plots in Jokioinen averaged 54% and in Vihti 37% to 41% of those harvested during the growing period. The effect of fertilizer application rate var- ied among trials. On clay soil, the increased fer- tilizer application rate did not result in increased DM yield when >50 kg N ha-1 was applied for the June+October harvest or for the seed stage Table 34. Effect of fertilizer application rate on mineral content (ash, SiO 2 , N, P, K) in dry matter of reed canary grass harvested in June and August, 1994 and in May, 1995 on clay soil in Jokioinen. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* Ash % June 9.1 8.7 8.5 8.6 8.7a Aug 8.7 8.3 7.9 8.1 8.3b May 6.5 5.7 5.3 5.2 5.7c *Means for N rate 8.1a 7.6b 7.2c 7.3c SiO 2 % June 3.9 3.1 2.6 2.3 3.0a Aug 4.6 3.6 3.0 2.8 3.5b May 5.7 4.8 4.4 4.3 4.8c *Means for N rate 4.7a 3.9b 3.4c 3.1d N % June 1.36 1.56 1.70 2.05 1.67a Aug 0.73 0.85 1.03 1.28 0.97b May 0.50 0.60 0.67 0.74 0.63c *Means for N rate 0.87a 1.00b 1.14c 1.36d P g kg-1 June 2.91 2.97 2.97 3.21 3.02a Aug 2.20 2.10 2.06 2.19 2.14b May 0.80 0.78 0.92 0.97 0.87c *Means for N rate 1.97a 1.95a 1.98a 2.12b K g kg-1 June 23.1 25.1 25.3 28.7 25.5a Aug 18.5 21.1 22.6 24.0 21.5b May 1.54 1.59 1.60 1.64 1.59c *Means for N rate 14.4a 15.9b 16.5b 18.1c * Means within the column or row followed by a different letter are significantly different (P<0.05). 51 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. harvest (Table 37). At delayed harvest in May 1995, 150 kg N ha-1 decreased yield significant- ly in comparison with 100 kg N ha-1 (P<0.0462). In 1995, all fertilizer treatments increased DM yield stepwise at the first harvest. At the seed stage, 50, 100 and 150 kg N ha-1 induced signif- icantly higher yield than the zero rate control, and at delayed harvest in May 1996 100 and 150 kg N ha-1 were associated with yield increas- es above those associated with 0 and 50 kg N ha-1 (P<0.01). On organic soil, harvest in June plus regrowth in October resulted in the highest yield in the first year, but higher fertilizer rates did not result in significant increase in yield above that from an application of 100 kg N ha-1 (Table 38). At the seed stage, the non-fertilized plots gave the lowest yields (P<0.05), but no dif- ferences were recorded among the various treat- ments. In 1995, the highest yields were record- ed when the crop was harvested at the seed stage in August. At delayed harvest in spring 1996, increasing fertilizer application did not affect DM yield. The regrowth biomass of tall fescue was har- vested during the beginning of October from the plots previously harvested in June at the flower- ing stage. The only source of yield variation of regrowth biomass in trials resulted from differ- ences in fertilizer application rate (Table 39). In 1994, the regrowth comprised, on average, 13% of the total DM yield on both soil types (Table 40), and in 1995, 25% on clay soil and only 9% o n o rg a n i c s o i l . F e r t i l i z e r a p p l i e d a t 1 0 0 and 150 kg N ha-1 in particular increased the re- growth capacity both on clay and organic soils (P<0.05). Table 35. Effect of fertilizer application rate on number of stems m-2 and proportion of stems, crude fibre and mineral content (ash, SiO 2 , N, P, K) in dry matter of reed canary grass in June and August, 1994 and in May, 1995 on organic soil in Vihti. Harvest N rate Number Proportion Crude Ash SiO 2 N P K kg ha-1 of stems of stems fibre % % % g kg-1 g kg-1 m-2 % % June 0 779 53.6 38.8 7.8 3.3 1.01 2.24 20.4 50 1087 51.7 39.7 7.7 2.6 1.17 2.32 23.4 100 1072 50.6 38.8 7.7 2.2 1.45 2.53 25.1 150 1094 48.8 39.1 7.8 2.1 1.61 2.53 25.3 Means for harvest 1008a 51.2a 39.1a 7.8a 2.6a 1.31a 2.41a 23.5a August 0 933 58.1 40.7 7.3 3.4 0.69 1.52 18.5 50 946 57.9 40.8 7.3 2.7 0.83 1.59 21.2 100 952 56.5 40.4 7.7 2.5 1.00 1.75 23.6 150 1010 55.7 39.5 7.9 2.2 1.10 1.84 23.9 Means for harvest 960a 57.0b 40.3b 7.5a 2.7a 0.90b 1.68b 21.8b May 0 779 63.2 45.8 5.9 5.0 0.52 0.92 1.70 50 989 60.4 46.4 5.1 4.2 0.51 0.89 1.61 100 809 62.2 46.2 4.8 3.9 0.64 0.95 1.53 150 625 62.1 45.5 4.8 3.8 0.71 0.99 1.50 Means for harvest 801b 62.0c 46.0c 5.1b 4.3b 0.60c 0.94c 1.58c *Means for N rate 0 830a 58.3a 41.8ab 7.0a 3.9a 0.74a 1.56a 13.5a 50 1007b 56.7b 42.3a 6.7b 3.2b 0.84b 1.60a 15.4b 100 944ab 56.4b 41.8ab 6.7b 2.9c 1.03c 1.74b 16.7c 150 910ab 55.5b 41.4b 6.8b 2.8c 1.14d 1.79b 16.9c * Means within the column and row followed by a different letter are significantly different (P<0.05). 52 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Table 36. Significance (P values) of differences in harvest timing, row spacing and fertilizer application rate for dry matter yield of tall fescue in 1994 and 1995 at Jokioinen and Vihti. Jokioinen Vihti Source 1994 1995 1994 1995 Row (R) 0.3915 0.1003 0.8584 0.2224 HR 0.3511 0.3349 0.1184 0.9762 Fertilizer (F) 0.0008 0.0001 0.0001 0.0001 HF 0.0001 0.0001 0.0015 0.0002 RF 0.1899 0.2842 0.3269 0.5225 HRF 0.4059 0.9887 0.6242 0.8798 Table 37. Effect of fertilizer application rate on total dry matter yield (kg ha-1) of tall fescue at different harvest timings in 1994 and 1995 on clay soil in Jokioinen. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June+Oct 9360 11080 11470 11760 10920a Aug 8220 8670 8830 8650 8670b May 4710 4530 4310 3980 4380c *Means for N rate 7430a 8190b 8200b 8130b 1995 June+Oct 4010 5430 6280 7390 5780a Aug 6090 7090 7150 7200 6880a May 3220 3630 4230 4670 3960b *Means for N rate 4440a 5380b 5920c 6420d * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 38. Effect of fertilizer application rate on total dry matter yield (kg ha-1) of tall fescue at different harvest timings in 1994 and 1995 on organic soil in Vihti. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June+Oct 12800 14120 15080 15760 14440a Aug 9190 10140 10780 11030 10280b May 3900 4090 3920 3980 3970c *Means for N rate 8630a 9450b 9930bc 10250c 1995 June+Oct 5880 8330 9260 9830 8320a Aug 8020 9170 10430 8950 9140b May 3740 3560 4130 4180 3900c *Means for N rate 5880a 7020b 7940c 7650c * Means within the column or row followed by a different letter are significantly different (P<0.05). Dry matter content of tall fescue Timing of harvest had the major effect on DM content of biomass on both soil types (Table 41). The biomass yields with highest DM content were harvested in spring (Tables 42 and 43). However, in spring 1996 the harvest was done as late as 30th of May in Vihti and the green shoots that had started to grow increased the 53 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. water content in the biomass (Table 43). The bi- omass of tall fescue harvested from non-ferti- lized plots had the lowest water content (P<0.05) at the flowering stage and in Jokioinen also at the seed stage. At delayed harvest in spring, the differences in biomass following application of different rates of fertilizer application were in- consistent and non-significant. Fertilizer application rate was the only source for variation in DM content of regrowth biomass in tall fescue harvested in October (Table 44). The DM content of regrowth yield (Table 45) was in most cases lower than that at June har- vesting (Tables 42 and 43). Only in 1995 in Jokioinen was the DM content of regrowth bio- mass higher than that in June. More fertilizer resulted in lower DM contents in 1994 (P<0.001) in both trials, but in 1995 only on organic soil (P<0.05) (Table 45). Number of stems of tall fescue The data on the number of stems m-2 are only given for tall fescue from Jokioinen since no sig- nificant differences attributable to differences in harvest timing, row spacing, and fertilizer ap- plication rates were observed in Vihti (Table 46); Table 40. Effect of fertilizer application rate on regrowth biomass (kg ha-1 measured in October) of tall fescue in Jokioinen and Vihti in 1994 and 1995. N rate kg ha-1 Means Harvest 0 50 100 150 for year 1994 Jokioinen 1250 1310 1510 1570 1410 1995 " 1200 1340 1550 1790 1470 1994 Vihti 1550 1600 2000 2440 1900 1995 " 490 600 770 1110 735 Table 39. Significance (P values) of differences attributable to row spacing and fertilizer application rate for regrowth biomass (measured in October) of tall fescue in Jokioinen and Vihti in 1994 and 1995. Jokioinen Vihti Source 1994 1995 1994 1995 Row (R) 0.2216 0.9188 0.4702 0.2629 Fertilizer (F) 0.0001 0.0001 0.0001 0.0001 RF 0.3739 0.8064 0.5789 0.0545 Table 41. Significance (P values) of difference in harvest timing, row spacing and fertilizer application rate effect on DM content of tall fescue in Jokioinen and Vihti in 1994 and 1995. Jokioinen Vihti Source 1994 1995 1994 1995 Harvest (H) 0.0001 0.0001 0.0001 0.0036 Row (R) 0.0916 0.3165 0.2709 0.3867 HR 0.1585 0.9419 0.6962 0.5949 Fertilizer (F) 0.0138 0.3560 0.1524 0.0111 HF 0.3595 0.0001 0.3196 0.1100 RF 0.3126 0.0213 0.4781 0.5473 HRF 0.2745 0.0129 0.0716 0.8206 54 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper where the number of stems ranged from 556 to 647 m-2. In Jokioinen, harvesting in spring re- sulted in 574 stems m-2, more than harvesting at the flowering stage (428 stems m-2) (P = 0.0374) or seed stage (485 stems m-2) (Table 47). Effects of fertilizer on the density of the tall fescue stand depended on the harvest time (Table 47). In June and August, the highest stem numbers were found when 50 kg N ha-1 was used, and in May in non-fertilized plots (P<0.05). Stem proportion of tall fescue In both trials, harvest timing and fertilizer ap- plication rate significantly affected the propor- tion of stems in tall fescue biomass. In Jokioin- en, the row spacing effect was also significant (Table 46). In both trials, stem proportion in- creased in biomass when plant growth proceed- ed during the summer, being highest at delayed harvest the following May (Tables 47 and 49). The highest stem proportions were found in non- fertilized plots. Increased fertilizer use decreased the relative amount of stems in biomass as hap- pened also with reed canary grass. In Jokioinen, the wider row spacing resulted in more stems in harvested yield (P = 0.0052) (Table 46). Crude fibre content of tall fescue In both trials (Tables 47 and 49), crude fibre content was significantly higher at delayed har- Table 42. Effect of fertilizer application rate and row spacing on dry matter content (%) of tall fescue in 1994 and 1995 on clay soil in Jokioinen. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June 30.6 29.9 29.2 29.5 29.8a Aug 41.4 39.7 39.4 39.4 40.0b May 91.5 91.8 91.8 91.1 91.5c *Means for N rate 54.5a 53.4b 53.4b 53.3b 1995 June 29.4 28.9 27.2 27.8 28.4a Aug 35.3 34.9 32.1 32.1 33.6b May 59.5 63.0 64.8 65.6 63.2c *Means for N rate 41.4a 42.3a 41.4a 41.3a * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 43. Effect of fertilizer application rate on dry matter content (%) of tall fescue in 1994 and 1995 on organic soil in Vihti. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* 1994 June 33.8 32.5 31.0 29.6 31.7a Aug 28.3 27.4 28.2 27.0 27.7a May 77.9 80.0 80.3 77.9 79.0b *Means for N rate 46.7 46.6 46.5 44.8 1995 June 33.5 32.1 30.9 30.2 31.6a Aug 37.7 36.7 37.3 38.4 37.5b May 42.9 41.7 38.2 39.2 40.4b *Means for N rate 37.8a 36.6ab 35.3b 35.7b * Means within the column or row followed by a different letter are significantly different (P<0.05). 55 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. vest than in June or in August (P<0.001). At the flowering stage and at delayed harvest, the crude fibre content was highest in the non-fertilized and 50 kg N ha-1 plots, both on clay and on organic soil (P<0.05). At the seed stage the fer- tilizer had less effect on crude fibre content. Row spacing affected crude fibre content only in Jokioinen where the wider row spacing induced Table 44. Significance (P values) of difference in row spacing and fertilizer application rate on dry matter content of regrowth biomass (measured in October) of tall fescue in 1994 and 1995 in Jokioinen and Vihti. Jokioinen Vihti Source 1994 1995 1994 1995 Row (R) 0.7998 0.5336 0.3400 0.1193 Fertilizer (F) 0.0001 0.4277 0.0001 0.0156 RF 0.2837 0.2152 0.2027 0.6478 Table 45. Effect of fertilizer application rate on dry matter content (%) of regrowth biomass (measured in October) of tall fescue in 1994 and 1995 on organic soil in Jokioinen and in Vihti. N rate kg ha-1 Means Harvest 0 50 100 150 for year 1994 Jokioinen 28.7 28.2 27.4 27.3 27.9 1995 " 29.3 29.7 29.3 29.3 29.4 1994 Vihti 25.4 24.5 24.0 23.3 24.3 1995 " 26.5 26.4 25.6 25.3 25.9 Table 46. Significance (P values) of differences in harvest timing, row spacing and fertilizer application rate effect on number of stems, stem fraction, crude fibre, and mineral content (ash, SiO 2 , N, P, K) of tall fescue in 1994 Jokioinen and Vihti. Number Stem Crude Ash SiO 2 N P K Source of stems fraction fibre Jokioinen Harvest (H) 0.0938 0.0001 0.0001 0.0001 0.0102 0.0001 0.0001 0.0001 Row (R) 0.5831 0.0052 0.0013 0.0165 0.0021 0.0087 0.2041 0.4219 HR 0.0897 0.3906 0.6229 0.5633 0.5089 0.4534 0.3462 0.3792 Fertilizer (F) 0.0543 0.0001 0.0001 0.0002 0.0095 0.0001 0.0001 0.0001 HF 0.0073 0.0287 0.0007 0.2793 0.0049 0.2409 0.0797 0.0001 RF 0.0719 0.0694 0.7835 0.9265 0.3964 0.7096 0.0555 0.6645 HRF 0.2324 0.4238 0.0265 0.1878 0.0626 0.6825 0.8537 0.8450 Vihti Harvest (H) 0.4786 0.0040 0.0001 0.0001 0.0147 0.0123 0.0001 0.0001 Row (R) 0.3578 0.1854 0.6908 0.4020 0.5425 0.5272 0.9818 0.9722 HR 0.9792 0.8178 0.0984 0.5057 0.6438 0.9130 0.6072 0.4816 Fertilizer (F) 0.1105 0.0050 0.0001 0.0073 0.0349 0.0001 0.0001 0.0008 HF 0.1095 0.0852 0.0002 0.0372 0.0001 0.2077 0.0007 0.0273 RF 0.7935 0.7007 0.3866 0.7599 0.0759 0.0844 0.1618 0.6035 HRF 0.3104 0.7275 0.1406 0.4982 0.9330 0.7241 0.3720 0.5175 56 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper s i g n i f i c a n t l y h i g h e r c r u d e f i b r e c o n t e n t (P = 0.0013). Ash content of tall fescue Unlike for reed canary grass, ash content of tall fescue was lower on clay than on organic soil. Harvest timing and fertilizer application rate af- fected ash content of tall fescue to a large de- gree, whereas row spacing had a significant ef- fect only on clay soil (Table 46). In both Jokio- inen (Table 48) and Vihti (Table 49) the ash con- tents of the plants harvested in May (4.4% and 5.2%, respectively) were significantly lower than in plants harvested in August (9.1% and 9.3%, respectively) or June (8.5% and 9.5%, respec- tively). On average, the lowest ash content was found in plants from non-fertilized plots and those from plots fertilized at 50 kg N ha-1. How- ever, in spring, the fertilizer had no clear effect on ash content in Jokioinen (Table 48). In Vihti, fertilizer application did not influence the ash content of biomass harvested at the seed ripen- ing stage (Table 49). In Jokioinen the 25 cm row spacing was associated with significantly lower ash content (P = 0.0165) than a row spacing of 12.5 cm. Silica content of tall fescue Silica (SiO 2 ) content of tall fescue was affected by harvest timing and fertilizer application rate on both soils (Table 46). Silica content of tall fescue was lower in plants harvested on clay soil (Table 48) than on organic soil (Table 49), be- ing respectively 2.4% and 3.2% at the flowering stage, 2.8% and 3.2% at the seed stage and 3.3% and 4.0% at delayed harvest. Harvesting during the 1994 growing period resulted in significant- ly lower silica content (P<0.05) than harvesting in May. Silica content was highest in non-ferti- lized plots and at 100 and 150 kg N ha-1 it de- Table 47. Effect of fertilizer application rate and row spacing on number of stems m-2, stem fraction and crude fibre (% of dry matter) of tall fescue in June and August, 1994 and in May, 1995 on clay soil in Jokioinen. Row spacing 12.5 cm Row spacing 25.0 cm N rate kg ha-1 N rate kg ha-1 Means for Harvest 0 50 100 150 Mean 0 50 100 150 Mean harvest time Number of stems June 538 568 386 454 288 424 442 324 428a Aug 506 518 386 320 526 668 404 552 485ab May 726 442 434 536 694 492 708 560 574b *Means for row spacing 485a 507a *Means for N rate 546a 519a 460b 458b Stem fraction % June 30.6 27.8 25.2 25.4 32.3 32.0 30.4 21.6 28.2a Aug 32.6 31.5 22.4 24.3 35.6 35.6 30.0 31.4 30.4a May 51.1 47.2 42.7 48.1 53.2 51.2 51.7 51.4 49.6b *Means for row spacing 34.1a 38.0b *Means for N rate 39.2a 37.5a 33.7b 33.7b Crude fibre % June 35.9 35.4 34.9 34.8 37.5 36.2 35.9 34.8 35.7a Aug 39.1 36.7 37.9 36.6 40.6 38.2 37.6 38.3 38.1b May 47.5 45.7 43.5 41.0 46.7 47.2 46.4 43.5 45.2c *Means for row spacing 39.1a 40.2b *Means for N rate 41.2a 39.9b 39.4b 38.1c * Means within the column or row followed by a different letter are significantly different (P<0.05). 57 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. creased significantly (P<0.05). There were no differences in effect among the various fertiliz- er application rates. Row spacing had a signifi- cant effect on silica content only on clay soil where the plots with the wider row spacing (25 cm) were associated with significantly low- er silica content (P = 0.0021). Nitrogen, phosphorus and potassium content of tall fescue Harvest timing and fertilizer rate had very sig- nificant effects (P<0.001) on the N, P and K con- tent of plants on both clay and organic soils (Ta- bles 46, 48 and 49). N content was lower the later the plants were harvested. Fertilizer appli- cation increased the N content in plants signifi- cantly at all rates and harvests in both trials. Row spacing had an effect on N content only on clay soil where the wider row spacing resulted in sig- nificantly lower N content (P = 0.0087). P content was lower the later the plants were harvested (P<0.01) (Tables 48 and 49). The high- est fertilizer application rate, 150 kg N ha-1, in- creased the P content in plants significantly at every harvest compared with the controls (clay P<0.01, organic P<0.001). The differences be- tween the effects of different fertilizer applica- tions varied depending on the harvest timing. At spring harvest, the highest rate resulted in a high- er P content compared with other treatments in both trials, but no significant differences between the other N rates were recorded. K content decreased during the winter, from 28.6 to 1.13 g kg-1 on clay soil and from 27 to 1.71 g kg-1 on organic soil (Tables 48 and 49). The effect of fertilizer application was depend- Table 48. Effect of fertilizer application rate on mineral content (ash, SiO 2 , N, P, K) in dry matter of tall fescue in June and August, 1994 and in May, 1995 on clay soil in Jokioinen. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* Ash % June 7.9 8.4 8.8 8.8 8.5a Aug 8.6 9.2 9.2 9.3 9.1a May 4.3 4.2 4.4 4.8 4.4b *Means for N rate 7.0a 7.3b 7.5bc 7.6c SiO 2 % June 2.7 2.4 2.3 2.2 2.4a Aug 3.1 2.8 2.7 2.5 2.8a May 3.3 3.2 3.3 3.5 3.3b *Means for N rate 3.0a 2.8b 2.8b 2.7b N % June 1.01 1.23 1.40 1.53 1.29a Aug 0.67 0.84 1.03 1.23 0.94b May 0.60 0.65 0.80 1.05 0.77c *Means for N rate 0.76a 0.91b 1.08c 1.26d P g kg-1 June 1.71 1.88 2.02 1.96 1.89a Aug 1.39 1.48 1.61 1.80 1.57b May 0.83 0.79 0.85 1.08 0.89c *Means for N rate 1.31a 1.38a 1.49b 1.62c K g kg-1 June 24.0 27.8 30.1 29.7 27.9a Aug 25.8 28.6 29.7 30.4 28.6a May 1.03 0.94 1.11 1.46 1.13b *Means for N rate 16.9a 19.1b 20.3c 20.5c * Means within the column or row followed by a different letter are significantly different (P<0.05). 58 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper ent on harvest timing in both trials (Table 46). In June and August, the K contents in non-ferti- lized plots were lower than in fertilized plots on clay soil (P<0.001). On organic soil, the differ- ence between the non-fertilized and fertilized plots in K content was observed only at the flow- ering stage (P<0.01). At delayed harvest no sig- nificant differences in K content were recorded among the fertilizer application rates. 5.2.2 Age of reed canary grass ley Dry matter yield The effect of harvest timing on DM yields var- ied among years (P = 0.0001) (Table 50). The lowest DM yields (t ha-1) were harvested at the beginning of the experiment in 1991 (spring) and 1992 (autumn) (Fig. 7a). Subsequently the yields were significantly higher, ranging from 6 to 8 t Table 49. Effect of fertilizer application rate and row spacing on stem fraction, crude fibre and mineral content (ash, SiO 2 , N, P, K) in dry matter of tall fescue in June and August, 1994 and in May, 1995 on organic soil in Vihti. N rate kg ha-1 Means for Harvest 0 50 100 150 harvest* Stem fraction % June 35.5 32.3 29.6 26.3 30.9a Aug 36.6 38.1 38.8 36.3 37.4b May 45.6 40.1 39.4 39.6 41.2c *Means for N rate 39.2a 36.8ab 35.9b 34.0b Crude fibre % June 36.4 35.4 34.8 34.5 35.3a Aug 39.4 37.7 38.7 37.4 38.3b May 46.8 44.5 43.1 41.1 43.9c *Means for N rate 40.9a 39.2b 38.8b 37.7c Ash % June 8.9 9.3 10.0 9.8 9.5a Aug 9.2 9.4 9.0 9.5 9.3a May 4.9 5.1 5.1 5.7 5.2b *Means for N rate 7.7a 7.9a 8.0ab 8.3b SiO 2 % June 3.5 3.1 3.2 2.9 3.2a Aug 3.7 3.3 2.9 2.9 3.2a May 3.7 4.0 3.9 4.4 4.0b *Means for N rate 3.6a 3.5ab 3.3b 3.4b N % June 0.94 1.10 1.30 1.58 1.23a Aug 0.73 0.90 0.91 1.21 0.94b May 0.64 0.77 0.93 1.14 0.87b *Means for N rate 0.77a 0.93b 1.05c 1.31d P g kg-1 June 2.38 2.53 2.73 3.00 2.65a Aug 1.69 2.10 2.05 2.60 2.11b May 1.02 1.09 1.19 1.35 1.16c *Means for N rate 1.70a 1.91b 1.99b 2.30c K g kg-1 June 25.7 28.8 30.3 29.9 28.7a Aug 25.9 27.2 27.2 27.7 27.0a May 1.68 1.59 1.68 1.91 1.71b *Means for N rate 17.8a 19.2b 19.7b 19.8b * Means within the column or row followed by a different letter are significantly different (P<0.05). 59 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. ha-1 on average. At the lower fertilizer rate, the age of the ley did not affect the spring harvested DM yield significantly, and the DM yields were relatively constant throughout the period 1992 to 1998. Among the autumn yields, only the yield in 1992 was significantly lower than the yields in the following years. The DM yields varied more at the higher fertilizer application rate and consequently the yield was more than 9 t ha-1 at both harvest times in 1997 (Fig. 7a). No signif- icant decrease or increase in yield was recorded as the ley aged, either when measured in autumn or in spring. Persistence of reed canary grass stand The reed canary grass plots harvested in spring remained free of weeds for 8 years, i.e., until spring 1999 when a small number of Elymus repens L. seedlings was found in plots. At au- tumn harvest and especially at the lower ferti- lizer application rate, the weed infestation was greater and particularly in 1996 the total harvest- ed biomass consisted of about 40% weeds in- cluding Taraxacum officinale L. and E. repens (Fig. 7b). Number of stems When number of stems and plant fractions were measured from the 25 x 50 cm sample taken in each plot before harvesting in 1992–1998, the results indicated that harvesting in spring result- ed in more straw (644 stems m-2) than harvest- ing at the seed stage (562 stems m-2). The results were, however, highly dependent on the year of harvest (Table 51). The older the stand, the few- er stems per m-2. At autumn harvest, the decrease was significant (3 first years vs. 3 last years) at both of the fertilizer application rates (P = 0.0036 and P = 0.0013). At spring harvest the decrease was smaller at the lower rate of 100 kg N ha-1 (P = 0.0782) and not significant at 200 kg N ha-1. Proportion of plant fractions Plant fractions, such as stem, leaf sheath, leaf blade and panicle, were analysed from yields harvested in 1992–1998 (Fig. 8). The proportion of stems in reed canary grass biomass was sig- Table 50. Significance (P values) of differences in fertilizer application rate, harvest timing and year effect on dry mat- ter (DM) yield, number of stems and proportion of stem fraction of reed canary grass harvested in 1991–1999. Source DM yield Number Stem of stems fraction Fertilizer (F) 0.0636 0.1983 0.6622 Harvest (H) 0.3103 0.1171 0.0001 FH 0.1160 0.9870 0.9713 Year (Y) 0.0023 0.0112 0.0001 FY 0.1365 0.5326 0.3242 HY 0.0001 0.0001 0.0171 FHY 0.0794 0.0110 0.8201 Table 51. Number of stems of reed canary grass in autumn and in spring yield at 100 and 200 kg N ha-1. 100 kg N ha-1 200 kg N ha-1 Means for Year Autumn Spring Autumn Spring year 1992 586 635 713 729 666a 1993 555 604 591 955 676a 1994 696 667 869 573 701a 1995 445 624 624 608 575ab 1996 344 549 464 853 553b 1997 472 425 530 512 485b 1998 456 629 523 653 565b * Means within the column followed by a different letter are significantly different (P<0.05). Table 52. Proportion of stem fraction (% of dry matter) in reed canary grass yield harvested in autumn and in spring as a mean of fertilizer rates of 100 and 200 kg N ha-1 in 1992–1998 in Jokioinen. Year Autumn Spring Means for year 1992 47.1a 48.4a 47.8a 1993 40.7b 54.1a 47.4a 1994 51.7a 58.6b 55.2b 1995 58.9c 70.5c 64.7c 1996 62.4c 75.1c 68.7c 1997 49.5a 61.9b 55.7b 1998 61.3c 64.0b 62.6bd Means for harvest 53.1a 61.8b * Means within the column or row followed by a differ- ent letter are significantly different (P<0.05). 60 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper nificantly (P = 0.0001) higher at spring (61.8%) than at autumn harvest (53.1%) (Table 52). The proportion of stem varied greatly depending on the year (P = 0.0001), being lowest in spring yield of 1992 and in autumn yield of 1993, whereas fertilizer had only a minor effect on pro- portion of stem. The stem yield (kg ha-1) varied depending on year (P = 0.0001), harvest timing (P = 0.0011) and fertilizer application rate (P = 0.0390) (Fig. 8). The stem yield harvested in spring (P = 0.0011) was on average 1200 kg ha- 1 higher than that harvested in autumn. The pro- portion of leaf blades averaged 27.1% and 19.4%, and leaf sheaths 16.9% and 18.8% of the DM yield, from autumn and spring harvests, re- Fig. 7. a) Dry matter (DM) yield kg ha-1, b) proportion of reed ca- nary grass (RCG) % of dry matter in 1991–1998 on clay soil in Jokioinen. N fertilizer rates 100 and 200 kg ha-1. spectively. Panicles were present only at the seed stage in autumn when they contributed 2.9% to DM yield (Fig. 8). Crude fibre content The crude fibre content of reed canary grass was analysed in 1991–1994. Only the harvest time and the harvest year affected the fibre content (Table 53). The content was higher when bio- mass was harvested in spring rather than in au- tumn (P = 0.0001). The fibre content increased significantly as plant stand aged (P = 0.0001) at both fertilizer application rates and harvests (Ta- ble 54). 61 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Fig. 8. Total dry matter (DM) yield of reed canary grass and proportion of plant fractions (1992–1999) harvested in August (A) and in spring (S) at 100 kg N ha-1 (1) and 200 kg N ha-1 (2) on clay soil in Jokioinen. Ash content The ash content of reed canary grass was meas- ured only in the initial four years of the experi- ment (Fig. 9a). The ash content was 6.7% of DM when the crop was harvested in spring, and the content decreased when the higher fertilizer ap- plication rate was used and in plants of aged stands (P<0.01). In autumn, the percentage was significantly higher (P = 0.0001); 8.4% on aver- age. Neither the fertilizer application rate nor the age of the grass stand affected ash content when harvested in autumn. Silica In addition to harvest timing and harvest year, fertilizer application rate affected the silica con- tent of reed canary grass (Table 53). Silica con- tent was significantly higher in material harvest- ed in spring (5.3% of DM) than in that harvest- ed in autumn (3.8% of DM) (Fig. 9b). Silica con- tent decreased from 6.2% to 4.2% in spring yield during the four years, but this was not the case for autumn yields. The higher fertilizer applica- tion rate resulted in lower silica content in both autumn and spring yields. Table 54. Content of crude fibre (% of dry matter) in har- vested reed canary grass yield in autumn and in spring at 100 and 200 kg N ha-1 in 1991–1994. Year Autumn Spring Means for year 1991 30.5a 38.5a 34.5a 1992 28.6a 37.5a 33.0b 1993 32.8b 41.2b 37.0c 1994 36.1c 44.2c 40.1d Means for harvest 32.0a 40.3b * Means within the column or row followed by a differ- ent letter are significantly different (P<0.05). Table 53. Significance (P values) of difference in fertilizer application rate, harvest timing and year effect on crude fibre, ash and SiO 2 content of reed canary grass in 1991– 1994. Source Crude fibre Ash SiO 2 Fertilizer (F) 0.5158 0.0881 0.0271 Harvest (H) 0.0001 0.0001 0.0004 FH 0.1634 0.0270 0.8551 Year (Y) 0.0001 0.0053 0.0024 FY 0.2058 0.3260 0.4425 HY 0.6917 0.0001 0.0003 FHY 0.2153 0.5162 0.3640 62 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Pulping characteristics Pulp yield, kappa number and screenings were measured only in the first and second years of harvest from two replicates. Harvest timing con- tributed most to the pulping characteristics (Ta- ble 55). Significantly higher pulp yield (P = 0.0010) and kappa number (P = 0.0045) were recorded from spring (41% of DM and 24.4, re- spectively) than from autumn harvests (35.1% and 18.5, respectively) (Fig. 10). Biomass har- vested in autumn was easier to pulp than bio- mass harvested in spring, and less screenings was recorded (P = 0.0009). The screenings averaged from 1.1% to 1.6% of DM in autumn and from 1.7% to 2.9% in spring harvests (Fig. 10). 5.2.3 Sowing time of reed canary grass The crop was sown in May, June, July, August and September in 1995 in Jokioinen. In May reed canary grass was sown with and without cover crop. DM yield, DM content, number of stems Fig. 9. a) Ash and b) silica (SiO 2 ) content % of dry matter (DM) of reed canary grass in August (au- tumn) and in May (spring) at 100 and 200 kg N ha-1 in 1991–1994 on clay soil in Jokioinen. Table 55. Significance (P values) of difference in fertilizer application rate, harvest timing and year effect on screened pulp yields, kappa numbers and amount of screenings in pulping experiments of reed canary grass. Source Pulp Kappa Screenings Fertilizer (F) 0.6924 0.5680 0.2528 Harvest (H) 0.0010 0.0045 0.0009 FH 0.0440 0.8682 0.0169 Year (Y) 0.3689 0.3100 0.4834 FY 0.3880 0.2033 0.8219 HY 0.0950 0.0414 0.0007 FHY 0.1893 0.0865 0.4227 63 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. m-2 and proportion of stem fraction in the total above-ground biomass were studied at spring harvests in 1997, 1998 and 1999. Dry matter yield and dry matter content Sowing time influenced DM yield of reed ca- nary grass (Table 56), being especially marked in the first year of harvest. In that case, sowing in May and June yielded more than sowing in July, August or September. In the following years, the yield differences were smaller. How- ever, the sum of the yield from three years was double if the reed canary grass stand was sown in May and June instead of August and Septem- ber (Table 57). DM yield was lowest in the first harvest year, independent of sowing times (P<0.05). DM content of harvested biomass was 84% or more in all cases except in 1997, when the biomass harvested from the plant stand sown in September was only 79.2% (Table 58). In 1998 harvested biomass was very dry over the whole trial area (DM content more than 90%). In 1998 and 1999, no differences in DM content were recorded among stands sown at different times. Number and proportion of stems In 1997 the number of stems was very high (988 stems m-2) in plots sown in May and low (356 Table 56. Significance (P values) of differences in sowing time and harvesting year effect on dry matter (DM) yield, DM content, number of stems and proportion of stem fraction of reed canary grass harvested in spring 1997, 1998 and 1999. Source DM yield DM content Number of stems Stem fraction Sowing time (S) 0.0001 0.0114 0.0003 0.2733 Year (Y) 0.0002 0.0007 0.2075 0.0143 SY 0.0132 0.1617 0.0035 0.0298 Table 57. Dry matter yield (kg ha-1) of reed canary grass sown on 30 May, 21 June, 22 July, 22 August and 20 September in 1995 and harvested in spring 1997, 1998 and 1999. Harvest Sowing time in 1995 year 30 May 21 June 22 July 22 Aug 20 Sept Means for year* 1997 5950a 5270b 2610c 1050d 960d 3170a 1998 7760ab 8370a 6040bc 5030c 4890c 6420b 1999 6670a 6650a 5780ab 4440b 4430b 5590b *Sums for sowing 20380a 20290a 14430b 10520c 10280c * Means within the row or column followed by a different letter are significantly different (P<0.05). Fig. 10. Screened pulp yield, kappa number and screenings % of dry matter (DM) reed canary grass in 1991 and 1992 at 100 and 200 kg N ha-1 on clay soil in Jokioinen. 64 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper stems m-2) in plots sown in September (Table 59). On average, establishing the ley in August and in September resulted in the lowest number of stems in harvested biomass (P<0.05). High num- bers of stems were not associated with high per- centages of stem fraction in this experiment. The highest number of stems was recorded in the first harvest year, when the lowest proportion of stem fraction, on average 57.9% of DM, was detect- ed (Table 59). In the following year the propor- tion of stem was higher (P = 0.0087). Sowing in August or September tended to result in lower stem fraction than earlier sowings, but no sig- nificant differences were attributable to sowing times. When the stem yields from three years were summed, the highest yields were recorded in stands sown in May and June (Fig. 11). Effect of cover crop When reed canary grass stands were established in May, using barley as a covering crop, DM yield decreased compared with the pure reed canary grass stand, when the yield was counted as a sum of the three recurrent harvesting years (Table 60). This was due to the lower yields in the first year associated with small proportions of stem fraction in harvested biomass. Of the two methods of harvesting the cover crop, cutting for Table 58. Dry matter content (%) of reed canary grass sown on on 30 May, 21 June, 22 July, 22 August and 20 September in 1995, and harvested in spring 1997, 1998 and 1999. Harvest Sowing time in 1995 year 30 May 21 June 22 July 22 Aug 20 Sept Means for year* 1997 89.8a 89.0a 88.8a 84.4a 79.2b 86.2a 1998 92.1a 92.2a 90.3a 92.1a 90.5a 91.4b 1999 87.0a 87.6a 85.5a 85.0a 85.1a 86.1a *Means for sowing time 89.6a 89.6a 88.2a 87.2ab 84.9b * Means within the row followed by a different letter are significantly different (P<0.05). Table 59. Number of stems m-2 and proportion of stem fraction (% of DM) of reed canary grass stands sown in 30 May, 21 June, 22 July, 22 August and 20 September in 1995, and harvested in spring 1997, 1998 and 1999. Harvest Sowing time in 1995 year 30 May 21 June 22 July 22 Aug 20 Sept Means for year Number of stems m-2 1997 988a 592b 690b 446b 356b 614a 1998 464a 648a 454a 296b 478a 468a 1999 598b 530b 792a 450b 614ab 596a *Means for sowing time 683a 590a 645a 397b 482b Stem fraction % of DM 1997 61.7ab 65.4a 55.4ab 49.7b 57.2ab 57.9a 1998 67.0a 70.9a 68.6a 67.2a 65.7a 67.9b 1999 64.8a 60.4ab 59.2ab 65.8a 57.9b 61.6a *Means for sowing time 64.5a 65.6a 61.1a 60.9a 60.3a * Means within the row followed by a different letter are significantly different (P<0.05). 65 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. silage at the end of August (Cover1) less advan- tageous for the development of the stand than threshing at the beginning of September. 5.2.4 Timing and stubble height of delayed harvested reed canary grass Dry matter yield and dry matter content Stubble height influenced significantly spring harvested DM yield of reed canary grass (Table 61). DM yield was on an average more than 30% higher (P = 0.0057) when the grass was harvest- ed at a stubble height of 5 cm instead of 10 cm (Fig. 12) in five successive years (1994–1999). The stubble height of 10 cm resulted in higher harvest losses, which can be explained partly by the loss of DM yield in higher stubble, and part- ly by the loss caused by lodging (Table 63). When the harvests taken in four successive weeks were compared in each year, the effect of harvest time on DM yield was dependent on the Fig. 11. Stem yield (kg ha-1) in reed canary grass stands sown in 1995, and harvested in spring 1997, 1998 and 1999 on clay soil in Jokioinen. Table 60. Dry matter (DM) yield (kg ha-1) and stem frac- tion (% of DM) of reed canary grass sown on 30 May, with barley as a cover crop removed as silage on 28 August (Cover1), removed by threshing on 5 September (Cover2), and without cover crop as a pure stand, harvested in spring 1997, 1998 and 1999. Harvest Cover1 Cover2 Pure stand Means for year year DM yield kg ha-1 1997 3130 3430 5950 3200a 1998 5290 7320 7760 6390b 1999 5910 6660 6670 5790b *Sums for sowing 14330b 17410a 20380a Stem fraction % of DM 1997 58.2a 55.7a 61.1a 58.3a 1998 68.3b 70.7b 66.9a 68.6b 1999 61.4b 65.2b 64.8a 63.8ab *Means for sowing 62.6a 63.8a 64.2a * Sums and means within the row followed by a different letter are significantly different (P<0.05). Table 61. Significance (P values) of difference in stubble height, harvest timing and harvest year effect on dry matter (DM) yield, content of stem fraction in DM yield, number of stems and stand height of reed canary grass harvested in spring. DM yield and stand height from the years 1994–1998, stem fraction and number of stems from 1995–1998. Source DM yield Stem Number Stand height fraction of stems in spring Stubble height (S) 0.0058 0.3953 0.8383 0.1737 Harvest (H) 0.0563 0.2063 0.7859 0.5744 SH 0.9172 0.7737 0.0539 0.3630 Year (Y) 0.0001 0.0001 0.0071 0.0001 SY 0.4800 0.6014 0.3290 0.2396 HY 0.0001 0.0046 0.0012 0.0001 SHY 0.0949 0.2081 0.0357 0.6072 66 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper age of the stand (P<0.01). After the second year the highest yield was recorded when plants were cut at 5 cm stubble height on the first possible day after the soil was dry enough to support har- vest machines in early spring (Fig. 12). The first possible harvest date varied yearly from 3rd to 11th May (Table 15). The crop was dry enough for harvesting, hav- ing a DM content of about 85%, usually a week before the soil was dry enough to support the harvester and it was possible to take the first cut. The DM content of the crop harvested at 5 cm varied from 77.6 to 90.8% at the first harvest (Fig. 12), being even higher when the crop was cut at 10 cm. During the weeks following the first harvest the DM content was affected both by the weather conditions (Fig. 12) as in 1996, when the second cut was done too soon after rain, and by the increasing amount of green material. The moisture content of the biomass increased until the 4th harvest as a lodged plant stand main- tained more moisture in harvested biomass and the amount of green material yield increased. The proportion of stem fraction was meas- ured in 1995–1998. On an average, the smallest stem proportion was found in biomass at the fourth harvest (Table 62), when it was delayed three weeks from the first harvest date. At the fourth harvest the variation of stem proportion was also smaller from year to year than at the earlier harvests. Also, the year was a significant source of variation. The highest stem proportions were measured in 1996 and 1997. The stubble height did not influence the proportion of stems significantly (Table 61). Development of the plant stand The first harvest date varied from 3rd to 11th May. The time between the first and the last har- vests was three weeks. The field was under snow cover until mid-April every year. As a result of the pressure of snow, plants lodged and the height of the lodged crop stand ranged between 16 and 24 cm annually without differences be- tween stubble heights monitored in previous years (Table 63). In 1994, 1997 and 1998 the entire stand lodged independently of stubble height or har- vest timing in previous years (Table 63). This prevented growth of green shoots, especially in 1997 (Fig. 13). In 1996 the stand was 72 cm high on average at the first harvest. Lodging of the crop increased during the subsequent weeks and at the last harvest the tops of green shoots were noted above the 20 cm high lodged crop stand. The new green shoots started to grow before the field was dry enough for harvesting and at the first cut the shoots were already 6–18 cm high. Three weeks later, the height of the shoots was 16–29 cm at the last harvest (Fig. 13). In 1997, the green shoot growth was delayed and shoots were found only sporadically among the harvest- ed material. The proportion of green matter in the yield remained small (Fig. 13), but its influ- ence on the moisture content of the yield was clearly seen in 1994 and 1995 (Fig. 12). Fig. 12. Dry matter (DM) (kg ha-1) and dry matter content (%) of reed canary grass harvested at stubble heights of 5 and 10 cm in 1994, 1995, 1996, 1997 and 1998 on clay soil, Jokioinen. Harvested DM yields are represented by col- umns and DM content by lines. Harvest timing: number of weeks after the first possible harvest date. 67 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. The proportion of green material in biomass was measured from samples taken before each harvest. The proportion of green shoots increased as spring advanced, being 3.5 to 5% of DM at the last harvest. In 1997, the amount of green shoots was less than 0.1%, even at the latest spring harvest. As the harvest was delayed for more than one or two weeks from the first pos- sible harvest date, the risk of excessive green matter in the harvested biomass increased sub- stantially. This was especially the case when the height of the green shoots was more than 20 cm and the sample was cut by hand at less than 5 cm above soil level. When a harvester was used, some of the green tops fell and the proportion of green shoots in harvested biomass was conse- quently smaller than in the samples harvested by hand. Because it was assumed that cutting the new plants at low stubble height may have had a re- straining influence on the developing stand, the stand height, and number of plants and panicles were also measured in autumn, when the plants were fully mature. The results in Table 64 show that stubble height had no significant effect on plant height, number of stems and number of panicles and only a modest effect on the content of the stem fraction measured in autumn 1997 and 1998 (Table 66). Harvest timing influenced plant height in Table 62. Effect of the harvest timing and year on the proportion of stem fraction % of dry matter (DM) and number of stems m-2 at spring harvest of reed canary grass in 1994–1998. Harvest timing: number of weeks after the first possible harvest date. Harvest timing 1995 1996 1997 1998 Means for harvest* Stem fraction % of DM 0 64.0a 70.6a 68.8a 59.6a 65.7ab 1 66.1a 69.6a 70.4a 60.4a 66.6ab 2 61.8a 75.1b 71.3a 60.6a 67.1a 3 62.6a 65.5c 65.9a 62.8a 64.1b *Means for year 63.6a 70.2b 69.3b 60.9c Number of stems m-2 0 610a 686a 545a 333a 544a 1 577ab 633ab 640ab 437ab 572a 2 685a 496b 477a 493b 538a 3 440b 672a 604ab 544b 565a *Means for year 578a 622a 566a 452b * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 63. Effect of the harvest timing and the harvest year on lodged stand height (cm) at spring harvest of reed canary grass in 1994–1998. Harvest timing: number of weeks after the first possible harvest date. Harvest timing Means for 1994 1995 1996 1997 1998 harvest* 0 18a 13a 72a 24a 17a 29a 1 21a 17a 54b 23a 14a 26a 2 26a 21a 45b 23a 15a 26a 3 29a 29b 25c 20a 17a 24a *Means for year 24a 20ac 49b 23ac 16c * Means within the column or row followed by a different letter are significantly different (P<0.05). 68 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper 1994 and 1995 when the late harvests resulted in shorter plants in autumn (Table 65). In 1996– 1998 no differences between the harvest timings were observed. The number of stems m-2 was lowest in autumn 1998 (Table 65). The number of panicles m-2 decreased significantly in 1997 and 1998, especially in late harvests (Table 65). In autumn, the content of stem fraction in bi- omass was affected significantly by harvest tim- ing (P = 0.0014) and year (P = 0.0001) (Table 64). The proportion of stems decreased when the har- vest was delayed more than one week (Table 66). The decrease from the first harvest to the fourth was significant in 1995 and 1997. In 1997 and in 1998, the stubble height also had an effect on pro- portion of stems, but the year effect was reversed. The stem fraction and the number of stems de- creased significantly from 1995 to 1998. Because of the large yield difference attrib- utable to differences in stubble height, the weight proportion of different fractions of single straws was investigated. The section 5–10 cm from the soil surface was particularly interesting. The weight of the straw fractions of 5 cm length was higher when the fractions were taken closer to the soil surface (Table 67). However, the dry weight of the 5–10 cm section was only 5.8% of the total biomass and it was not the only reason for the yield difference resulting from cuts at two stubble heights. The weight cm-1 of the straw was higher at the base of the straw. DM content of straw fractions was 58% in fractions of 0–5 cm and 63% in fractions of 5–10 cm. In plant parts from 25 cm above soil level to the top of the canopy the DM content was 85%. Fig. 13. The height of the green shoots (cm) and the amount of green material (% of dry matter) in spring 1994–1998. Harvest tim- ing: number of weeks after the first possible harvest date. Table 64. Significance (P values) of differences in stubble height, harvest timing and harvest year effect on plant height, the number of stems and panicles, and content of stem fraction of reed canary grass in autumn 1995–1998. Source Plant height Stems Panicles Stem fraction Stubble height (S) 0.1122 0.6112 0.9723 0.4623 Harvest (H) 0.2321 0.2601 0.0363 0.0014 SH 0.9160 0.8499 0.4089 0.9314 Year (Y) 0.0001 0.0083 0.0001 0.0001 SY 0.8576 0.5425 0.6092 0.0065 HY 0.0005 0.5488 0.1590 0.0045 SHY 0.4312 0.5200 0.7425 0.7990 S h o o ts c m G re e n % o f D M 69 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. 5.3 Research on reed canary grass varieties 5.3.1 Commercial cultivars of reed canary grass at delayed harvesting The productivity of ten commercial cultivars or breeding lines of reed canary grass (R-90-7587, Palaton, Vantage, Rival, Jo 0510, Motterwitzer, Barphal 050, Venture, Lara and VåSr 8401) was Table 65. Effect of the harvest timing and the harvest year on plant height (cm), number of stems m-2 and panicles in autumn 1994–1998. Harvest timing: number of weeks after the first possible harvest date. Harvest timing Means for 1994 1995 1996 1997 1998 harvest* Plant height in autumn cm 0 155a 170a 181a 168a 163a 167a 1 152a 168a 179a 165a 165a 166a 2 148ab 159b 181a 168a 167a 164a 3 144b 155b 181a 169a 166a 163a *Means for year 150a 163b 180c 167b 165b Number of stems in autumn m-2 *Means for year 553a 560a 668b 548a 450c Number of panicles in autumn m-2 0 174 326 242 73 108 185a 1 217 288 178 45 95 165ab 2 193 264 192 43 80 154bc 3 173 182 206 45 90 139bc *Means for year 189a 265b 204a 52c 93d * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 66. Effect of harvest timing and the harvest year on the content of stem fraction (% of dry matter) of reed canary grass measured in autumn in 1995–1998. Harvest timing 1995 1996 1997 1998 Means for harvest* 0 69.0a 68.0a 61.1a 63.8a 65.5a 1 67.4a 67.9a 58.2b 64.4a 64.5ab 2 66.9a 66.3a 57.8b 63.5a 63.6bc 3 61.9b 65.7a 59.6b 62.6a 62.4c *Means for stubble Stubble 5 cm 66.9a 66.8a 60.9a 62.4a Stubble 10 cm 65.7a 67.1a 57.5b 64.7b *Means for year 66.3a 67.0a 59.2b 63.5c * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 67. Dry weight, proportion in dry matter (DM), den- sity and DM content of fractions of single straws of reed canary grass. Straw Weight Proportion Weight DM content fraction g % g cm-1 % 0–5cm 0.109 7.5 0.022 58.1 5–10cm 0.084 5.8 0.017 63.0 10–15cm 0.078 5.3 0.016 72.5 15–20cm 0.078 5.4 0.016 76.0 20–25cm 0.074 5.1 0.015 80.4 25–35cm 0.144 9.9 0.014 85.2 35cm→top 0.886 61.0 0.012 84.7 70 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper studied in seven Finnish locations. DM yield of the cultivars was compared at spring harvests in 1996–1999. The cultivars studied grew well at all exper- imental sites (Tables 69, 70, 71, 72, 73, 74 and 75), even in Lapland (Table 74) (Fig. 14). How- ever, variation between growing sites and har- vest years were substantial. For this reason the results are presented separately for each experi- mental site. Significant differences between the cultivars were observed in each trial, but the dif- ferences were highly dependent on the year (Ta- ble 68). In Tohmajärvi (Table 75), the experi- ment was interrupted after the first spring har- Fig. 14. Dry matter (DM) yield (kg ha-1) of reed canary grass cultivars harvested in spring. A different letter above the column means that the harvested yields for cultivars are significantly different (P<0.05). 71 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Table 68. Significance (P values) of differences in cultivar and harvesting year effect on dry matter yield of reed canary grass grown in Jokioinen, Laukaa, Ylistaro, Ruukki, Sotkamo, Rovaniemi, and Tohmajärvi. Source Jokioinen Laukaa Ylistaro Ruukki Sotkamo Rovaniemi Tohmajärvi Cultivar (C) 0.0001 0.0001 0.0222 0.0227 0.0005 0.0001 0.0319 Year (Y) 0.0031 0.7540 0.0001 0.0001 0.0001 0.0001 – YC 0.0001 0.0001 0.0334 0.0015 0.0001 0.0101 – Table 69. Dry matter yields (kg ha-1) of reed canary grass cultivars at spring harvests in Jokioinen, 1996– 1999. Cultivar 1996 1997 1998 1999 Means for cultivar* R-90-7587 6870a 8210a 9670a 7194a 7990a Palaton 6940a 7470b 10100a 7393a 7970a Vantage 6420a 8420a 8680a 7440a 7740a Rival 5430b 7380b 10250a 6756a 7450a Jo 0510 7040a 6700b 10550a 8235a 8130a Motterwitzer 5270b 6780b 11170a 5942b 7290b Barphal 050 7115a 8230a 7970a 6867a 7550ab Venture 5530b 7380b 9600a 6397a 7230b Lara 5680b 6980b 8390a 7107a 7040b VåSr 8401 5050b 5430c 7100a 5587b 5790c *Means for year 6130a 7300b 9350c 6890ab * Means within the column (cultivar) or row (year) followed by a different letter are significantly differ- ent (P<0.05). Table 70. Dry matter yield (kg ha-1) of reed canary grass cultivars at spring harvests in Laukaa, 1996–1998. Cultivar 1996 1997 1998 Means for cultivar* R-90-7587 6340ab 6460ab 5200ab 6000a Palaton 6880ab 7210a 4590a 6220a Vantage 7100a 6930ab 4430a 6150a Rival 5650b 6310ab 6930b 6300a Jo 0510 6710ab 5830b 7130b 6560ac Motterwitzer 6170ab 6370ab 6590b 6380a Barphal 050 6890ab 7760a 7790b 7480b Venture 6820ab 5630b 7340b 6600a Lara 6380ab 7370a 7570b 7100c VåSr 8401 6210ab 6530ab 6560b 6430a *Means for year 6510a 6640a 6410a * Means within the column (cultivar) or row (year) followed by a different letter are significantly differ- ent (P<0.05). vest in 1996 because the experimental station was closed. The cultivars Barphal 050 and Lara were productive, especially in the northern sites Rovaniemi (Table 74) and Sotkamo (Table 73) and also in Laukaa (Table 70) where the snow cover is moderately thick during winter. In the same locations Motterwitzer, Venture and line R-90-7578 were the most sensitive to the north- 72 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper Table 71. Dry matter yield (kg ha-1) of reed canary grass cultivars at spring harvests in Ylistaro, 1996– 1998. Cultivar 1996 1997 1998 Means for cultivar* R-90-7587 11180a 10260a 4280ab 8570a Palaton 13980a 8330ab 4660ab 8990a Vantage 8470bc 10070a 5430a 7990a Rival 8450bc 7970ab 5440a 7290ab Motterwitzer 6660c 6580b 4040ab 5760b Barphal 050 6870c 5870b 3510b 5420b Venture 11080a 9550a 4310ab 8310a Lara 11310a 9080a 4580ab 8320a VåSr 8401 10250ab 6430b 4250ab 6980a *Means for year 9810a 8240b 4500c * Means within the column (cultivar) or row (year) followed by a different letter are significantly differ- ent (P<0.05). Table 72. Dry matter yield (kg ha-1) of reed canary grass cultivars at spring harvests in Ruukki, 1996–1999. Cultivar 1996 1997 1998 1999 Means for cultivar* R-90-7587 2710a 7420a 8370a 5460ab 5990a Palaton 2730a 6920a 7630ab 5110ab 5600a Vantage 3010a 7530a 7990ab 5570ab 6030ac Rival 2420a 6960a 6370b 4650b 5100ab Jo 0510 3020a 8210a 8830a 6800c 6710c Motterwitzer 2420a 6660a 7480ab 5020ab 5400a Barphal 050 2200a 6850a 6910ab 5570ab 5390ab Venture 2490a 5440a 6710ab 4620b 4810ab Lara 2770a 8320a 8140a 6020abc 6320c VåSr 8401 2680a 7630a 6660ab 6470ac 5860a *Means for year 2650a 7200b 7510b 5530c * Means within the column (cultivar) or row (year) followed by a different letter are significantly differ- ent (P<0.05). Table 73. Dry matter yield (kg ha-1) of reed canary grass cultivars at spring harvests in Sotkamo, 1996– 1998. Cultivar 1996 1997 1998 1999 Means for cultivar* R-90-7587 3650a 7110a 7740a 6330a 6210a Palaton 4590b 6360a 8580a 6260a 6450a Vantage 5010b 6270a 8260a 7370b 6730a Rival 5120b 8470a 7660a 6700a 6990a Motterwitzer 3230a 6480a 6830b 5710a 5560b Barphal 050 4970b 7900a 9140a 7010b 7260c Venture 3940a 7000a 8260a 5860c 6260a Lara 5420c 6660a 8440a 6950b 6870a VåSr 8401 4560b 6960a 6390b 5180d 5770b *Means for year 4500a 7020b 7920c 6370b * Means within the column or row followed by a different letter are significantly different (P<0.05). 73 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. ern conditions. Jo 0510, Palaton, Lara, and Van- tage were productive in the trials situated in western Finland, Jokioinen (Table 69), Ylistaro (Table 71) and Ruukki (Table 72). 5.3.2 Mineral and fibre content of plant parts in reed canary grass cultivars The proportion of different plant parts (stems, leaf sheaths, leaf blades and panicles) of three cultivars (Palaton, Venture and Lara) of reed canary grass from three locations (Jokioinen, Ylistaro and Ruukki) was analysed from sam- ples collected in spring 1997. Mineral composi- tion (ash, Si and K) and the amount of crude fi- bre were analysed in each plant fraction except panicles. The pulping characteristics, including pulp yield, amount of screenings, kappa number and fibre dimensions, were determined from the plant material harvested in spring 1998. Proportion of plant fractions The principal component of spring harvested biomass of reed canary grass was stem fraction (65–74% of DM) (Fig. 15). The proportion of leaf sheaths was 12–16%, and leaf blades 11– 20% of DM. The number of panicles represent- ed less than 0.5% of biomass harvested in spring. Lara had more leaves than other cultivars in Jokioinen and Ruukki. However, in Ylistaro the proportions of plant parts in different cultivars were almost equal. No significant trial site and cultivar effect was found on the proportion of stem fraction (Table 76). Mineral and fibre content of plant parts The contents of ash, silica, potassium and crude fibre of the plant parts are shown for each experimental site as there were large differenc- e s b e t w e e n t h e s i t e s p a r t i c u l a r l y f o r a s h Table 74. Dry matter yield (kg ha-1) of reed canary grass cultivars at spring harvests in Rovaniemi, 1997– 1999. Cultivar 1997 1998 1999 Means for cultivar* R-90-7587 1990a 2390a 3730a 2710a Palaton 4440b 3290a 4640a 4120b Vantage 2770ac 3700a 5450ab 3980b Rival 3170bc 4710ab 5830ab 4570b Jo 0510 3800b 2630a 4740a 3720ab Motterwitzer 1900a 4820b 6320b 4350b Barphal 050 4620b 5850b 7180bc 5890c Venture 1750a 2620a 4680a 3020a Lara 4420b 5640b 6810bc 5620c VåSr 8401 4630b 5890b 6300b 5610c *Means for year 3350a 4150b 5570c * Means within the column or row followed by a different letter are significantly different (P<0.05). Table 75. Dry matter yield (kg ha-1) of reed canary grass cultivars at spring harvest in Tohmajärvi, 1996. Cultivar 1996* R-90-7587 5140ac Palaton 6730b Vantage 5740ac Rival 5700ac Motterwitzer 5330ac Barphal 050 5490ac Venture 6010ab Lara 5820abc VåSr 8401 4970c Means for year 5660 * Means within the column followed by a different letter are significantly different (P<0.05). 74 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper (P = 0.0068), silica (P = 0.005) and potassium content (P = 0.0107) (data not shown). The high- est amounts were found in Jokioinen and the low- est in Ruukki (in stem fraction) and Ylistaro (in leaf fractions). However, in Ruukki, a heavy wind caused soil contamination in winter 1997 resulting unusually high ash, silica and potassi- um content in both leaf blades and leaf sheaths. For crude fibre, the experimental site had a mi- nor effect. Significant differences in mineral and fibre content were found between different plant parts of the reed canary grass in every experimental site (P = 0.0001). In Jokioinen and Ylistaro, cul- tivars also differed significantly in ash and sili- ca content (Table 77) and in Jokioinen, in crude fibre content in addition. Fig. 15. The proportion (% of dry matter) of plant parts of reed ca- nary grass cultivars harvested in spring 1996 in Jokioinen, Ylistaro and Ruukki. Table 77. Significance (P values) of differences among cultivars and plant parts in ash, silica, potassium and crude fibre content in dry matter of reed canary grass grown in Jokioinen, Ylistaro and Ruukki. Source Ash SiO 2 K Crude fibre Jokioinen Cultivar (C) 0.0089 0.0091 0.1370 0.0156 Plant part (P) 0.0001 0.0001 0.0001 0.0001 CP 0.6635 0.0515 0.0039 0.0398 Ylistaro Cultivar (C) 0.0414 0.0256 0.3375 0.0942 Plant part (P) 0.0001 0.0001 0.0001 0.0001 CP 0.7009 0.8772 0.2843 0.8452 Ruukki Cultivar (C) 0.1070 0.1107 0.3813 0.4322 Plant part (P) 0.0001 0.0001 0.0001 0.0001 CP 0.0550 0.1698 0.7280 0.1441 Table 76. Significance (P values) of difference among trial sites, cultivars and their interactions on proportion of stem fraction in harvested biomass of reed canary grass grown in Jokioinen, Ylistaro and Ruukki. Source P-value Trial site (T) 0.0704 Cultivar (C) 0.0977 TC 0.2674 75 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. The significantly lowest ash, silica and po- tassium contents were found in stems and the highest in leaf blades (Tables 78, 79 and 80). The highest fibre contents were obtained also in stem fractions in every location (Table 81). The min- eral and fibre contents of leaf sheaths were in- termediate between stem and leaf blade fractions. In all locations, and in all plant parts, the high- est ash, silica and potassium contents were re- corded for Lara (Tables 78 and 79). In Jokioin- en and Ylistaro the difference between Lara and the other two cultivars was significant (P<0.05) in ash and silica content. The content of crude fibre in reed canary grass differed among plant parts (P = 0.0001). The stem fraction had the highest fibre content, from 48.0 to 52.1% of DM (Table 81). In Jokio- inen and Ylistaro, Lara had a lower fibre con- tent than Palaton and Venture in all plant parts. The difference between Lara and Venture was significant at both sites. Table 79. SiO 2 content (% of dry matter) of stems, leaf sheaths and leaf blades of three reed canary grass cultivars grown in Jokioinen, Ylistaro and Ruukki. Cultivar Means for Plant part Palaton Venture Lara plant part* Jokioinen Stem 3.4 3.2 4.5 3.7a Leaf sheath 5.2 5.0 6.8 5.7b Leaf blade 7.2 7.7 9.4 8.1c *Means for cultivar 5.3a 5.3a 6.9b Ylistaro Stem 2.1 2.1 3.1 2.5a Leaf sheath 3.6 3.8 4.6 4.0b Leaf blade 5.0 5.2 6.1 5.4c *Means for cultivar 3.6a 3.7a 4.6b Ruukki Stem 1.8 1.7 1.8 1.8a Leaf sheath 4.51) 3.31) 4.61) 4.1b Leaf blade 9.41) 7.71) 9.11) 8.7c *Means for cultivar 5.2a 4.3a 5.2a * Means within the column (plant part) and the row (cul- tivar) followed by a different letter are significantly dif- ferent (P<0.05). 1) soil contamination Table 78. Ash content (% of dry matter) in stems, leaf sheaths and leaf blades of three reed canary grass cultivars grown in Jokioinen, Ylistaro and Ruukki. Cultivar Means for Plant part Palaton Venture Lara plant part* Jokioinen Stem 4.2 4.1 5.9 4.7a Leaf sheath 7.0 6.8 9.1 7.6b Leaf blade 10.4 10.3 12.5 11.1c *Means for cultivar 7.2a 7.1a 9.2b Ylistaro Stem 3.2 3.0 4.3 3.5a Leaf sheath 5.5 5.7 6.4 5.9b Leaf blade 7.6 8.1 9.2 8.3c *Means for cultivar 5.4a 5.6a 6.6b Ruukki Stem 2.8 2.6 3.1 2.8a Leaf sheath 7.31) 5.51) 7.51) 6.7b Leaf blade 15.91) 12.51) 16.11) 14.8c *Means for cultivar 8.7a 6.8a 8.9a * Means within the column (plant part) and the row (cul- tivar) followed by a different letter are significantly dif- ferent (P<0.05). 1) soil contamination. Table 80. Content of K (g kg-1 of dry matter ) of stems, leaf sheaths and leaf blades of three reed canary grass cultivars grown in Jokioinen, Ylistaro and Ruukki. Cultivar Means for Plant part Palaton Venture Lara plant part* Jokioinen Stem 0.6a 0.7a 0.9a 0.7a Leaf sheath 1.1b 1.3b 1.8b 1.4b Leaf blade 4.4c 2.3c 2.5b 3.1c *Means for cultivar 2.0a 1.4a 1.7a Ylistaro Stem 1.1 1.3 1.4 1.2a Leaf sheath 1.6 2.0 1.9 1.8b Leaf blade 2.2 2.4 2.7 2.4c *Means for cultivar 1.6a 1.9a 2.0a Ruukki Stem 1.6 1.4 2.6 1.9a Leaf sheath 2.41) 2.41) 3.11) 2.6b Leaf blade 4.31) 4.01) 4.91) 4.4c *Means for cultivar 2.7a 2.6a 3.5a * Means within the column (plant part) and the row (cul- tivar) followed by a different letter are significantly dif- ferent (P<0.05). 1) soil contamination 76 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper of reed canary grass from different localities. The results are presented as means for the three ex- perimental sites. The total pulp yield and the screened yield from stems was over 50% at kap- pa 10 (Table 82), whereas leaf sheaths gave yields of only about 42% and leaf blades 32% at higher kappa numbers. High pulp yield of the stem fraction was associated with high crude fi- bre content and kappa number (Fig. 16). Leaf blades also gave dark coloured pulps with low brightness and proved thus to be totally unsuita- ble for pulping. Because of the low quality of leaf blades and sheaths, pulps from entire plants cooked slower, gave significantly lower yield and pulp brightness than stems, but kappa num- bers of same level as stem fractions. The black liquor pH after cooking whole plants was as high as after cooking the stems (pH 12.8) indicating the same delignification rate. The fibre length and dimensions of different plant parts varied greatly (Fig. 17). Stem fibres were 0.86 mm long and they were longer than those in leaves. A coarseness of 0.09 to 0.10 mg m-1 showed stem, leaf sheaths and even the whole plants to be more suitable for papermaking than fibres from leaf blades. Fibre length in pulp from the whole plant was about 0.8 mm and coarseness 0.10 mg m-1, which was significantly higher than the respective fibre properties in leaf sheaths and blades (Fig. 17). Table 81. Crude fibre content (% of dry matter) of stems, leaf sheaths and leaf blades of three reed canary grass cul- tivars grown in Jokioinen, Ylistaro and Ruukki. Cultivar Means for Plant part Palaton Venture Lara plant part* Jokioinen Stem 50.2 52.1 48.6 50.3a Leaf sheath 39.4 39.8 37.2 38.8b Leaf blade 28.2 30.1 27.6 28.7c *Means for cultivar39.3ab 40.7a 37.8b Ylistaro Stem 50.1 51.7 48.0 50.0a Leaf sheath 41.4 42.3 39.3 41.0b Leaf blade 29.1 29.2 26.7 28.4c *Means for cultivar40.2ab 41.1a 38.0b Ruukki Stem 50.3 49.8 50.0 50.1a Leaf sheath 41.0 41.5 38.5 40.3b Leaf blade 25.9 27.3 25.9 26.4c *Means for cultivar39.1a 39.5a 38.2a * Means within the column (plant part) and the row (cul- tivar) followed by a different letter are significantly dif- ferent (P<0.05). Table 82. Results from the pulping experiments and crude fibre analyses of different plant parts of reed canary grass har- vested in spring 1998. Significance (P value) of difference in plant part effect on the variables. DM = dry matter. Variable Whole Stems Leaf Leaf P value plant sheaths blades Total pulp yield (% of DM) 46.6b 51.7a 41.7c 31.9d 0.0001 Screened pulp yield (% of DM) 46.2b 51.2a 41.6c 31.9d 0.0001 Kappa number 12.1c 10.0c 16.0b 21.3a 0.0016 Brightness (%) 30.0b 40.0a 23.3c 10.7d 0.0001 Black liquor pH 12.5ab 12.8a 12.2b 11.7c 0.0011 Fibre length (mm) 0.82a 0.86a 0.56b 0.48c 0.0001 Fibre width (µm) 16.6a 16.9a 16.1a 16.4a 0.6182 Fibre coarseness (mg m-1) 0.10b 0.09b 0.10b 0.20a 0.0001 Cwt index 4.5a 4.6a 4.8a 4.3a 0.2687 Crude fibre (% of DM) 44.5b 51.9a 42.5b 31.4c 0.0001 Means within the row (plant part) followed by a different letter are significantly different (P<0.05). Pulping characteristics of plant fractions Samples from different parts of reed canary grass showed significant variation in all their pulping characteristics (Table 82). Minor differences were found in the fibre and pulping properties 77 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Stems had the highest crude fibre content (52% of DM). Crude fibre content of whole plants was closer to that of leaf sheaths than of stems. Fi- bre width of reed canary grass was approximately 16.5 m, and plant part had no significant effect on it (Table 82). CWT index of the fibres of reed canary grass was 4.6 and was not dependent on plant part. Fig. 16. Total pulp yield vs. a) kappa number and b) crude fibre content of dry matter (DM) in stems, leaf sheaths, leaf blades and entire plant of reed canary grass (cv. Pala- ton) harvested in spring 1998. Samples were collected from Jokioinen, Ylistaro and Ruukki. Fig. 17. Fibre properties of unbleached sulphate pulps made of stems, leaf sheaths, leaf blades and entire plants of reed canary grass (cv. Palaton) harvested in spring 1998. Sam- ples from Jokioinen, Ylistaro and Ruukki. 6 Discussion When this study was started in 1990, the short- age of short fibre raw material for the pulp in- dustry was, and still is, marked in Finland. The study aimed at finding a non-wood plant spe- cies that could be used as short fibre raw mate- rial for pulping and papermaking to substitute for the considerable importation of birch. The properties considered important for a fibre crop were high yielding ability, good pulping quali- ty, good adaptation to the prevailing climatic conditions, possibilities for low cost production using existing farm machinery, possibilities for 78 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper domestic seed production (Table 9), and availa- bility throughout the year. Thus, our demands were similar to those voiced by Nieschlag et al. (1960): “A new fiber crop must fit the technical requirements for processing into pulp of accept- able quality in high yield and must also be adapt- able to practical agricultural methods and eco- nomically produce high yield of usable dry mat- ter per acre”. A focus of this study was to find a species with the described properties above. An additional goal was to develop crop management to enhance formation of fibre yield from the most promising species. This discussion is dealing with the entire production chain with emphasis on crop management results. 6.1 Strategy used for selecting species for non-wood pulping During the first stages of the study 17 species were chosen for preliminary pulping tests and mineral analysis. The species chosen were known to be high yielding crops and several spe- cies, e.g. common reed and straw of cereals had already been frequently used for pulping (Misra 1987, Hurter 1988). Hemp, nettle and linseed straw were studied, because their long bast fi- bres are known to be good raw material for pa- permaking (Kilpinen 1991, Ilvessalo-Pfäffli 1995). However, during the very early stages of the study the focus was on short fibre crops, for which monocotyledons, including four grasses and four cereal species, were of better quality in pulping tests, but had higher mineral content than the dicotyledons studied. The number of crop species evaluated in this study was much lower than that in experiments of Nelson et al. (1966). However, on the basis of the screening, only reed canary grass, tall fescue, meadow fescue, spring barley, goat’s rue, red clover and lucerne were selected for further studies. Results of additional studies showed that perennial grasses with good pulping quality and adaptability to Finnish growing conditions had an advantage over the dicot species in this study. Reed canary grass and tall fescue were especial- ly promising species for pulping (Pahkala 1997) and hence, development of crop management began with these species in order to improve their yielding capacity and pulping quality. However, as a result of additional experience over two years it was evident that tall fescue was not com- petitive since its yielding capacity and number of stems decreased rapidly if harvested in spring. Therefore, subsequent studies focused solely on production of reed canary grass. The strategy and the criteria used for selection of the fibre plant are described in the flow-chart in Fig. 18. 6.2 The preconditions for production of acceptable raw material for non-wood pulping 6.2.1 Possibilities to enhance yielding ability Harvesting time The harvesting system greatly influenced yield capacity of the species. Tall fescue was favoured by a harvesting system of two cuts (first cut at flowering and second in October) to a greater extent than reed canary grass. The superiority of the two-cut system compared with three or one cut systems was reported in earlier studies (Nissinen and Hakkola 1994, Pahkala 1997). Two cuts of reed canary grass resulted in lower yields, especially on organic soil. In the years of experimentation, regrowth DM yield of reed canary grass comprised 5% to 32% and tall fes- cue 9% to 25 % of total harvested biomass. The regrowth ability was highly dependent on weath- er conditions during the post-harvest period. Pre- cipitation after the first cut contributed marked- ly to the regrowth. In the studies of Mason and Lachance (1983), performed in Quebec, Cana- 79 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. da, 43% of total biomass of tall fescue was from regrowth and for reed canary grass it was 32%. The total DM yield of two cuts of reed canary grass and tall fescue however tended to decrease after the first year of harvest. Furthermore, for papermaking purposes the system of two har- vests, combined with drying the biomass, is like- ly to be too expensive even when the combined biomass from two cuts would be high during the first harvest years. High DM yields of reed canary grass and tall fescue were obtained when the crops were har- vested in autumn at the seed ripening stage. However, the DM content was less than 45% for both species, and the harvested biomass needed to be dried to reach a DM content of 85% before storage (Hemming et al. 1996). Reed canary grass gave the highest yields when harvested only once either in autumn or the following spring. However, the annual variation in yield was greater when harvested in autumn. Accord- ing to the studies of Mason and Lachance (1983), total annual yields of reed canary grass and tall fescue increased when the first harvest was de- layed. In their study, reed canary grass was su- perior in yielding capacity to timothy (Phleum Fig. 18. Flow-chart for the selection of fibre plant. 80 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper pratense L.), tall fescue and Kentucky bluegrass (Poa pratensis L.). Moreover, in Swedish stud- ies reed canary grass had the highest yield po- tential when it was compared with brome grass (Bromus inermis Leyss.), tall fescue, cocksfoot (Dactylis glomerata L.) and timothy (Wisur et al. 1993). Of the crop species studied, reed canary grass was favoured most by a spring harvest. The first spring harvest was done two years after sowing and it resulted in 4–7 t DM ha-1. The following spring harvests gave yields of 6–8 t ha-1 in most years. DM yields increased with delayed harvest and increasing age of the ley compared with au- tumn harvests. This was also demonstrated in Swedish studies (Olsson 1993, Andersson 1994, Landström et al. 1996). Spring yields of reed canary grass were 6 to 10 t ha-1 annually and on organic soil even higher than 10 t: twice the an- nual yield of birch forest (4–7.5 t of DM ha-1), the maximum annual growth of which is 8–15 m3 (Ferm 1993). When reed canary grass was harvested in spring, the yield remained constant from the second year ley throughout eight years, but some variation caused by weather conditions was recorded in those years. The difference be- tween the average yield at autumn and spring harvests was not significant during the eight years because of the first harvest year, which was associated with the lowest yields in every ex- periment. Reed canary grass would benefit from spring harvesting with good persistence of the stand and with small variation in yield. Howev- er, its productivity in the UK was 7–12% less than that of Miscanthus and switchgrass (Chris- tian et al. 1999). For tall fescue, delayed harvesting in spring resulted only in 37–54% of DM yields harvest- ed during the previous growth period. Low spring yields of tall fescue were associated with the growth habit of the species: a plant stand of tall fescue consisted mostly of leaves, and the crop was flattened tightly along the ground un- der snow cover. In spring, it was impossible to lift the lodged biomass with harvesters, and the plants were partly rotten. After spring harvest, tall fescue produced much fewer stems and pani- cles than the plots harvested in summer or au- tumn. As a tussock grass, tall fescue may be more prone to damage during an early spring cut than reed canary grass. The reason for the enhanced formation of reproductive tillers could be also the lack of light in late summer of the previous year, when the tillers of tall fescue were initiat- ed or when the tillers were too young in autumn to respond to low temperature induction (Hare 1993). The enhanced effect of shading on tiller formation was reported for cocksfoot (Hare 1994). Because of poor biomass and straw yield, tall fescue was considered not to be suitable for spring harvesting. The spring harvest duration of the present studies was about 10–15 days, when the mois- ture content of the grass was between 10% and 15%. The moisture content decreased to this lev- el even before ice had disappeared from soil, i.e. in south Finland in late April. High moisture content of the soil or rain showers occasionally delayed harvesting for weeks. Hemming et al. (1996) estimated that during the harvest period of two weeks in spring there would be 6–9 days when the weather conditions favour harvesting in Finland. It was also obvious that the harvest- ing has to be done before the new tillers are 15– 20 cm high. If the emerging shoots are taller at harvest, they may drastically reduce quality of the harvested biomass because of increasing moisture and mineral content of the biomass. In literature this is called the “harvest window” problem. It is described for Miscanthus in the Netherlands (Huisman 1994, Venturi and Huis- man 1997). It is the period between the possible start of the harvest, defined by the decreasing moisture content of soil and biomass in spring time, and the end of the harvest period when the tillers grow too long. Effect of nutrients Increase in the supply of mineral nutrients from the deficiency range increases the growth of crop plants. The positive yield response to nitrogen application is well known for grasses (MacLeod 1969, Hiivola et al. 1974, Allinson et al. 1992, Gastal and Bélanger 1993). In this study, the in- 81 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. creased fertilizer application rates usually result- ed in increased total yield of reed canary grass, when the biomass was harvested at the green stage in summer or in autumn. However, on a clay soil the yield increase with increasing fer- tilizer application rates was obvious also in spring up to 150 kg N ha-1. A rate of 200 kg N ha-1 did not improve yield beyond that promoted by 100 kg N ha-1. On organic soil, the spring yield response to increasing fertilizer rates was smaller than on clay soil and applications in excess of 50 kg N ha-1 did not result in higher DM yields. The results show that growing reed canary grass on clay soil requires more N fertilizer to reach the same DM yield as growing the crop on or- ganic soil. Overuse of fertilizers may be uneco- nomic and cause environmental problems for farmers. Fertilizers represent the principal cost in cultivating reed canary grass when the rate of 70 kg N ha-1 is exceeded (Maunu and Järvenpää 1995). When reed canary grass was grown on clay soil and harvested in spring the economic optimum for the fertilizer application rates is likely to range from 50 to 100 kg N ha-1. Grow- ing reed canary grass on organic soil for paper- making might be advantageous as less fertilizer is required. However, more research is needed to have further long-term information on devel- opment and yield formation of reed canary grass on organic soil. Yield of tall fescue was not enhanced at the highest fertilizer application rate of 150 kg N ha-1 during the two first years of harvest. On clay soil there were hardly any differences among the various treatments beyond 50 kg N ha-1 when tall fescue was harvested at the green stage. On or- ganic soil, the yield response for the highest rate was recorded only at the seed stage in 1995. However, the results of Moyer et al. (1995) from young tall fescue swards showed yield increase by 53% as N application rate increased from 13 to 112 kg N ha-1, and by 69% as the rate increased from 13 to 168 kg N ha-1. At delayed harvesting in spring the differences in yield among the treat- ments seemed to be inconsistent and not statis- tically significant. If tall fescue is used as raw material for papermaking, fertilizer application rates higher than 100 kg N ha-1 are not likely to improve yield. Harvest losses Stubble height markedly affected the harvested DM yield of reed canary grass. When grass was harvested at 5 cm instead of 10 cm, the DM yield was on an average more than 30% higher. The reasons for such a high yield difference may be several. When cut at the height of 10 cm versus 5 cm, the loss of the total biomass measured as the weight loss of 5 cm straw was 5.8%. The higher harvest losses at a stubble height of 10 cm caused by lodging were also evident, but were not measured in this study. In the study of Hor- rocks and Washko (1971), plants cut in spring leaving 10 cm stubble instead of 4 cm produced the same number of tillers, but the weight per tiller after a 4 cm cut was about 60% higher than that after a 10 cm cut. In the present study, the number of stems counted in autumn and spring was not affected by stubble height. However, the weight of individual tillers was not measured and the high yield, when cut at 5 cm, remained part- ly unexplained. Harvesting losses resulting from the harvester and baling would be high, but un- der favourable conditions were less than 15% (Hemming et al. 1996). The summary of the fac- tors affecting harvested DM yield of reed canary grass is presented in Fig. 19. 6.2.2 Development of crop management practices targeting high quality Fibre content High fibre content in raw material is desirable for fibre production. In this study, the crude fi- bre content of reed canary grass and tall fescue was always higher the later the crops were har- vested, being thereby highest at spring harvest. Reed canary grass and tall fescue crude fibre contents were highly correlated with pulp yield (Hemming et al. 1996, Pahkala et al. 1999). An increase of fibre content with delayed harvest is explained by ageing of the plant, and is associ- 82 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper ated with increase in the relative amount of plant cell walls (cellulose and lignin content in par- ticular). This takes place at the expense of other cell constituents as described for several forage crops (Buxton and Hornstein 1986, Albrecht et al. 1987, Buxton and Russel 1988, Gill et al. 1989). Another possible reason for fibre increase at delayed harvesting would be the different weight distribution of the plant parts in harvest- ed biomass. The cell wall concentration, and thus the fibre content, is highest in stems (Buxton and Hornstein 1986), and the proportion of stems increased with plant age at the expense of the leaf fraction (Olsson et al. 1991, Pahkala and Pihala 2000). In this study, the highest pulp yield and crude fibre content was measured for stems and the lowest for leaf blades. Thus, the propor- tion of stems is likely to be a determining factor contributing to fibre content of the total biomass. However, even more than a half of the biomass of reed canary grass consisted of stems, where- as the corresponding proportion in tall fescue was 30–45%. In spite of this difference, the crude fibre content of total biomass, as well as the pulp- ing results from earlier studies (Pahkala 1997), was almost the same. The result indicates that the leaf fraction of tall fescue, unlike that of reed canary grass, contains fibres suitable for pulp- ing. The fertilizer application rate had rather a small effect on crude fibre content of reed ca- nary grass and tall fescue especially in spring harvested biomass. However, the lowest content of crude fibre was often found in plants that had received the most fertilizer. Increased fertilizer use decreased the relative amount of stems in biomass and concomitantly fibre content. It in- creased the proportion of leaves more than that of stems. The highest stem proportion of reed canary grass and tall fescue was found in plots where the total DM yield was lowest, in most cases in non-fertilized plots or in those that had received 50 kg N ha-1. Mineral content The quality of paper pulp is dependent on qual- ity and homogeneity of the biomass used as raw material, as well as the impurities that often orig- inate from soil. When entire plants are used for pulping, heterogeneity in fibre and mineral con- tent of the raw material can result in variation in the quality of the pulp (Ilvessalo-Pfäffli 1995). In fibre production, mineral elements such as silicon can complicate the recovery of chemi- cals and energy in pulp mills and cause thereby extra costs (Ranua 1977, Keitaanniemi and Fig. 19. Factors affecting spring yield of reed canary grass (RCG). 83 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. Virkola 1982, Rexen and Munck 1984, Jeyasin- gam 1985, Ulmgren et al. 1990). Other harmful elements for the pulping process include potas- sium, chlorine, aluminium, iron, manganese, magnesium, sodium, sulphur, calcium and nitro- gen (Keitaanniemi and Virkola 1982). In the present study, the concentrations of undesirable minerals were higher in non-wood species than in birch, and the concentrations in grasses and cereals were generally higher than those in di- cotyledons. The total mineral content, indicated as ash content, was lowest in straw of linseed and hemp and highest in nettle and barley. High silica concentrations are known to be typical of grass species (Ilvessalo-Pfäffli 1995, Marschn- er 1995), because grasses accumulate silica in epidermal cells, where it protects the crop against herbivores and fungi (Jones and Handreck 1965). If grass biomass is used as a fibre source for paper manufacturing evidently more silica and other minerals enter the process than when wood is used. However, results from this study showed that it is possible to decrease the mineral con- tent of the raw material by modifying crop man- agement practices such as harvesting time, fer- tilizer application rate, soil type and by using the plant parts with the lowest mineral content as raw material. The chemical composition of a plant part varies depending on the stage of de- velopment when the mobile elements move from organ to organ as growth proceeds (Jeffrey 1988). The ash content decreased as plants aged, being lowest in spring yield, as Landström et al. (1996) also showed. The potassium and nitro- gen content was clearly lower in spring than in autumn. This was probably due to leaching dur- ing winter. The trend was the same for both plant species and occurred irrespective of plant part (Pahkala and Pihala 2000). Contrary to this, sil- ica content clearly increased as harvesting was delayed, being highest in spring yield of reed canary grass and tall fescue. In several earlier studies, the concentration of silicon was found to increase as a plant aged (Tyler 1971) and was highest in dried material at delayed harvest (Landström et al. 1996, Burvall 1997). Silicon is deposited as silica crystals mostly in the epi- dermis of plants (Ilvessalo-Pfäffli 1995) and it is not exposed to leaching. When studying min- eral content of each plant part, ash and silica content were lowest in stems irrespective of the harvest time. In leaf sheaths and especially in leaf blades, the content of minerals was clearly higher than in stems. Petersen (1989) reported high ash and silica content in leaves of cereals and Theander (1991) in leaves of reed canary grass. In addition to a yield response, mineral nu- trition can influence the mineral composition of a plant. Increase in fertilizer application rate el- evated potassium, nitrogen and phosphorus con- tent, whereas ash and silica content decreased. The highest contents of ash and silica were found in plants from non-fertilized plots. When har- vested during the growing period, silica content decreased when fertilizer application rate in- creased for both species, but in reed canary grass the stepwise decrease was seen also in spring yield. Soil type affected mineral content of bio- mass. The lowest ash and silica content was found in plants grown in sandy and organic soil and highest in those from clay soil. Thus, our results indicated that it is possible to produce high quality raw material for pulping, i.e. high fibre content and low mineral content, by com- bining moderate fertilizer application to a grass crop with spring harvesting. When the increase in the stem fraction of biomass is realized by this means, it also results in improved quality of raw material. The density of grass stands is often an im- portant measure in regulating canopy structure. Using the wider row spacing of 25 cm, rather than the more standard 12.5 cm, did not result in a yield or quality advantage for reed canary grass. In tall fescue, the effect of row spacing was more obvious than for reed canary grass, especially on clay soil. In Jokioinen, the wider row spacing resulted in more stems in biomass of tall fescue, lower ash and silica content and higher crude fibre content. The increased stem proportion following the use of wider rows pos- sibly contributed to improved quality of tall fes- cue. 84 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper 6.2.3 Possibilities for reducing production costs When grasses are grown for paper pulp, their crop management differs from that used in con- ventional grassland farming. As short fibre raw material the price for grass at the mill gate can- not be much higher than that for birch. Accord- ing to calculations of Paavilainen et al. (1996b) and Hemming et al. (1996) the price for a ton of dry reed canary grass should be 389 to 421 FIM (65–71 euros) at maximum, whereas the corre- sponding price for birch or pine was 472 to 479 FIM (79–81euros) at a reference mill. High bio- mass yield and high pulp yield are the most im- portant factors contributing to profitability when raw material is produced for the fibre industry. 6.2.4 Requirements and possibilities for domestic seed production Except for lucerne, nettle, fibre hemp and com- mon reed, the species screened at the first stage of this study seed can be produced on a com- mercial basis in Finland, or it has at least been shown to be possible. Results from the study of Sahramaa and Hömmö (2000b) showed that seed production for reed canary grass is possible in Finland, but seed yield and vigour, i.e. germina- tion ability and seed weight, varied greatly de- pending on year and harvesting time. At the op- timum harvest time, 15 days after completion of anthesis, the seed yield of reed canary grass was 100 to 369 kg ha-1, i.e., close to the level report- ed in Sweden (280–361 kg ha-1, Cedell 1994). The yield was highest in one- and two-year old plant stands and the high seed yield was associ- ated with high 1000 -seed weight and high seed germination ability. Commercial seed production of reed canary grass has started on 400 hectares, but stability problems exist, i.e. yield decrease already at the second harvest year has been re- corded (Myllylä and Myllylä 2000). A possible solution would be to harvest the seed once and then use the crop in the following years for fibre or energy or harvest the seed only every other year, as recommended by Myllylä and Myllylä (2000) for the commercial seed growers. Tall fescue is not commonly grown in Fin- land. However, a new cultivar, Retu, was re- leased in 1995. It is a highly persistent, winter hardy cultivar and following its release the area sown to tall fescue has increased from zero to 1000 ha within the last five years. In the official variety trials, the average seed yield for tall fes- cue has only been 395 kg ha-1 as a result of poor panicle production (Niemeläinen 1994). How- ever, seeds of tall fescue did not shatter as easi- ly as those of reed canary grass, and thus, seed production would be easier. The low seed yields will keep the price high, as is also the case with reed canary grass. 6.2.5 Enhanced adaptability of reed canary grass to Finnish growing conditions Selecting an appropriate cultivar or breeding a new one are principal means for optimising adaptability and thus, high yielding capacity and quality for the prevailing growing conditions. The ten cultivars included in the study were all bred for feed. Thus, their growth habit and pro- ductivity were rather similar. The quality traits for a biomass crop differ from those for fodder crop. For example, decreasing alkaloid content of the biomass by breeding may increase attack by insect pests or herbivores (Coulman et al. 1977, Østrem 1987). The ideotype of reed ca- nary grass for fibre use has high stem to leaf ra- tio, high fibre content and low mineral content (Andersson and Lindvall 1999), and is in these respects dissimilar to a fodder type. In this study, it was not possible to identify the highest yield- ing cultivar for each location because of large genotype x harvest year interactions for DM yield. The spring yield was often highest in the second or third year of spring harvest. In Rov- aniemi, the most northern trial site, the develop- ment a sufficiently dense stand took a year longer 85 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. than elsewhere. The annual average DM yields were 6 to 7 t ha-1. However, the highest yields, 11 t ha-1 in Jokioinen and 14 t ha-1 in Ylistaro, indicated the high yield potential of the crop. Yields could have been even higher if the trials had been harvested in spring following the first harvest; spring harvest of the variety trials start- ed after two years of autumn harvest. Large DM yield is one of the main goals in breeding agrofibre crops (Lindvall 1992, Sah- ramaa and Hömmö 2000a). However, the varia- tion among growing sites and among harvesting years was more substantial than variation among cultivars. The cultivars Barphal 050 and Lara tended to be most productive at the northernmost sites, Rovaniemi and Sotkamo, whereas Motter- witzer and Venture were the most sensitive ones in the extreme growing conditions. Barphal 050 and Lara were productive also in Laukaa, where the snow cover is thick in winter. Jo 0510, Pala- ton, Lara, and Vantage were more productive in the trials in western Finland, Jokioinen, Ylistaro and Ruukki. The variation in quantitative traits including yield capacity is controlled polygeni- cally, the relative effect of which is smaller than that arising from environmental factors such as climate, nutrition and crop management (Baltensperger and Kalton 1958, Sachs and Coul- man 1983, Østrem 1988a, Falconer and Mackay 1996). Studies on the morphology and quality of three cultivars (Palaton, Venture and Lara) indi- cated only modest variation in proportion of plant parts. The cultivars were bred for feed pur- poses and thus their growth habits were rather similar. There were no significant differences between growth at the three locations (Jokioin- en, Ylistaro and Ruukki), which indicates that the growth habit of each genotype was independ- ent of the location and prevailing soil type. How- ever, when the fibre and mineral content of each plant part was studied, all plant parts of cultivar Lara contained lower fibre but higher mineral content than those of Venture and Palaton. Thus, Lara was concluded to be less suitable for fibre production. When testing the reed canary grass breeding material, variation in stem proportion and mineral and fibre content were recorded (Sah- ramaa and Hömmö 2000a). The reason for the variation in mineral content has been studied in Miscanthus populations collected from Japan. The large variation in nitrogen and potassium contents in the spring harvested Miscanthus were related to degree of crop senescence in autumn (Jørgensen 1997). The first severe frost in the autumn increased the rate of mineral loss from plant material. If the effect of autumn frost on the mineral content in spring yield is evident, as Jørgensen (1997) suggested, early senescence of the plant stand is very important when produc- ing raw material for pulping due to less miner- als in harvested biomass. Since the quality of the current cultivars bred and grown for feeding purposes was not satisfac- tory for fibre use, a new type of grass cultivar adapted to northern growing conditions is evident- ly needed. Breeding programs aimed at develop- ing such cultivars for non-food purposes began in 1993 in Finland and in 1989 in Sweden (Lind- vall 1997, Andersson and Lindvall 1999, Sah- ramaa and Hömmö 2000a). In contrast to culti- vars bred for feeding purposes, substantial mor- phological variation has been found within the breeding material collected from different loca- tions in Finland and in Sweden (Lindvall 1999, Sahramaa and Hömmö 2000a). As some variation in chemical components of interest has also been found in the breeding material, it is likely that new cultivars, targeted for fibre production pur- poses, can be released in the future. The interest in producing reed canary grass for non-food pur- poses has therefore not ceased. 6.3 Feasibility of non-wood pulping Pulping grass biomass and cereal straw was easy and fast. It took only 10 to 15 minutes, when the soda-anthraquinone process was used for pulp- ing at the first screening of species. Processing 86 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper wood took at least 90 minutes. Only modest dif- ferences between the monocotyledons were found. Pulp yields were 33 to 40% of DM for grasses harvested during the green stage, and 42 to 48% for cereal straw. Pulp yields for dicoty- ledons were much lower and the amount of un- cooked screenings, which is insignificant in com- mercial birch sulphate pulp and less than 3% for grasses and cereal straw, was up to 41% for di- cotyledons. The cooking procedure was the same for all species, which is likely to explain the unsatisfactory pulping result for dicotyledons. Probably short cooking time was more suitable for the monocots. Also the amount of NaOH (16% of DM) used in trials was too low for di- cotyledons. In the case of red clover and goat’s rue the pulp yield, the amount of screenings and kappa number became more acceptable when the dose of cooking chemical was increased to 20% or 24% of DM. In the present study, delayed harvesting great- ly affected pulping characteristics of reed canary grass by increasing both kappa number and pulp yield. Biomass harvested in autumn was easier to pulp than that harvested in spring, and less screenings were recorded. The screenings aver- aged from 1.1% to 1.6% of DM in autumn and from 1.7% to 2.9% in spring harvest. The kappa numbers, indicating lignin content (Håkansson et al. 1996), were lower for grass pulp than for wood pulp or for pulp made from legumes and other dicots. In grasses and legumes, lignins are predominantly formed from coniferyl and si- napyl alcohols with only small amounts of p- coumaryl alcohol (Buxton and Russel 1988). However, large variation in lignin structure and content exists among the major crop groups and among species (Sarkanen and Hergert 1971, Gross 1980). During maturation of grass, sy- ringyl lignin increases in proportion relative to guaiacyl and p-hydroxyphenyl lignins (Carpita 1996). The increased lignin content and espe- cially syringyl lignin would explain higher kap- pa number and screenings in biomass harvested in spring. Samples from different parts of reed canary grass showed significant variation in all their pulping characteristics. Only fibre width or CWT index (indexed value of cell wall thickness) of reed canary grass did not differ among plant parts. Stems are the most useful plant part, giv- ing the highest yield, lowest kappa number un- der constant cooking conditions, and the bright- est pulp. The stem fraction was the most suita- ble for fibre production since it contained the lowest mineral content and the highest content of crude fibre. This resulted in the highest pulp yield. Spring harvesting and fractionation of the raw material, especially removal of the leaf blades, reduced the mineral content and im- proved the pulpability and papermaking poten- tial of reed canary grass (Paavilainen et al. 1996b). Stem fibres with a fibre length of about 0.9 mm and a coarseness of about 0.09 mg m-1 were best suited for papermaking. Large amounts of fine material originated from epidermal and parenchymal cells of leaf blades, which also made the sheets more difficult to dewater as re- ported also by Wisur et al. (1993). Stems had the highest crude fibre content, being 52% of DM. Crude fibre content of whole plants was closer to that of leaf sheaths than that of stems. Leaf blades also gave dark coloured pulps of low brightness and thus proved to be completely un- suitable for pulping. Because of the low quality of leaf blades and sheaths, the pulps from whole plants cooked slower and gave significantly low- er yield and pulp brightness than stems alone. Kappa number was about the same as for stem fraction. Removing the undesirable minerals along with the leaf blades would reduce the min- eral content considerably and, simultaneously the relative proportion of stem, the most fibre-rich part of the crop, would increase. Using a higher proportion of stem fraction would increase the pulp yield and improve the pulp quality as shown by Petersen (1989) and Paavilainen et al. (1996b). When a crop was harvested in spring, the total pulp yield correlated with crude fibre content of the plant part (Pahkala et al. 1999). Crude fibre, measured using the Weende analyt- ical system, has been a standard method for more than a century for determining fibre in animal and human foods (van Soest 1985). From cell 87 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 10 (2001): Supplement 1. wall constituents, the crude fibre determination yields cellulose, and a small fraction of hemi- cellulose and lignin. The remaining hemicellu- lose and lignin, and even a fraction of cellulose, is dissolved using a combination of acid and al- kali. Pulp yield determined by chemical pulping and measures the same fibre fractions: cellulose, some hemicellulose and a part of the lignin. Thus, the crude fibre content of grass may serve as an indicator of pulp yield. At the pulp mill, leaves, dust and dirt can be removed by air fractionation before cooking (Paavilainen et al. 1996b). However, in grasses the leaf sheath is usually tightly rolled around the stem, being thereby more difficult to remove than leaf blades. Mechanical pretreatment im- proves the quality of the pulp by increasing bleachability and decreasing the fines and silica particles in the raw material. Removing 40% of the silica through pretreatment of the grass (Paavilainen et al. 1996b) can decrease the amount of silicon entering the process. The de- watering and drying ability of pure grass pulps can be improved by mechanical fractionation and blending the grass pulp with long-fibre softwood pulp (Wisur et al. 1993. Paavilainen et al. 1996a, Paavilainen et al. 1996b). Based on the result of a pilot test, reed canary grass pulp is a potential short fibre component for fine papers in blends with long fibres from soft wood pulp. No runna- bility problems were found in the pilot process when the amount of reed canary grass sulphate pulp was increased to 70% of the pulp blend (Paavilainen and Tulppala 1996). Dewatering and drying characteristics also stayed constant. This result differed from that obtained in Swe- den (Wisur et al. 1993), where unfractionated, short-chopped green reed canary grass was dif- ficult to dewater. Increased grass pulp affected some of the paper properties important for run- nability on the paper machine and for printabil- ity of the paper. Tear strength was decreased, but optical properties and paper surface properties including smoothness and gloss were improved (Paavilainen and Tulppala 1996). Pulp yield and quality have been improved through crop man- agement and pulping processes suited to the raw material. The development stage of the crop at harvesting greatly affected the amount and qual- ity of the pulp. When late summer harvested reed canary grass was delignified using ethanol as the pulping chemical, kappa number stayed high (50–65) using an even cooking time of two to five hours (Håkansson et al. 1996). The pulping method may also influence paper properties such as tear strength and the light scattering coeffi- cient (Thykesson et al. 1998). 7 Conclusions This thesis describes a strategy and a process to locate, select and introduce a crop for a new pur- pose. The steps taken along the process over- lapped during the ten years of research, but the goal, to have a new fibre crop for domestic short fibre production, remained clear throughout the study. In conclusion, the concept of large-scale cultivation of a new fibre crop, reed canary grass, is described as a result of crop management re- search conducted in 1990–2000. Baling, storage and transport were described by Hemming et al. (1996). Crop management practices for reed canary grass as a forage crop were well established even though the grass was not commonly grown in Finland. In growing reed canary grass for fibre, the best time for sowing was spring or early sum- mer, although the slowly emerging seedlings became subject to weed competition and drought. Small seeds, with a 1000 seed weight of about 0.9 g, were sown at 800 to 1000 viable seeds m-2 (i.e., 7–10 kg ha-1). This gave a dense stand if sown without a cover crop at a depth of 1 cm and using rows spaced at 12.5 cm. A double row 88 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper spacing resulted in more weeds, and lower bio- mass yield with less stems. Even though the nat- ural habitat of reed canary grass is wet and flood- ed areas, it grows on almost any soil type. It was relatively drought tolerant after the seedling stage, but on heavy clay soils establishment was uneven. Using more seed may ensure establish- ment on clay soil. However, reed canary grass established well and produced high biomass on humus-rich wet soils and sandy soils. It tolerat- ed flooding well, and grew even in an area inun- dated with seawater at low salt concentration. The amount of nutrients removed from the field with the harvested crop varied considera- bly and depended on harvest time. At spring har- vest, only half of the supplied N and P were re- moved with the crop. The supplied K was in bal- ance with that removed, 6 t ha-1. On organic soil, which is very suitable for reed canary grass, low- er fertilizer application rates can be successful- ly used. Nitrogen fertilizer was applied to stands of reed canary grass at 40 to 70 kg ha-1 at estab- lishment and in the first harvest year and during subsequent seasons at 70 to 100 kg ha-1, depend- ing on the desired yield and soil type. Reed canary grass typically yielded 7–8 t ha-1 within three years of sowing on clay soil and exceeded 10 t ha-1 on organic soil after the sec- ond harvest year. The optimum harvest time for reed canary grass for pulp production was spring. The harvest period allowed by weather condi- tions ranged from 10 to 15 days in Finland. At that time the moisture content of the non-viable grass biomass was between 10% and 15% and the maximum height of the new, green tillers 15 to 20 cm. The stubble height strongly influenced harvested yield. If the plant stand was cut to 10 cm from the soil surface, the DM yield was 30% lower than when cut to 5 cm. Harvesting can be performed by mowing followed by baling. Un- der favourable conditions, harvest losses were less than 15%. Storage of round bales was cost- effective in simple outdoor stacks covered by plastic. The economical transport distance of the bales to a pulp mill was estimated to be about 50 km (Hemming et al. 1996). When cut in the spring, reed canary grass was very persistent and grew well for at least 10 years. The stem was the most valuable part of the plant from the per- spective of pulping performance, containing more fibre than other plant parts. The content of undesirable minerals was also lowest in the stem, and especially in spring harvests, in which the stem content was often 60 to 70% of the DM yield, increasing with plant stands age. The cultivars of reed canary grass currently grown in Finland were solely bred for forage. One of the most important properties of a culti- var for pulping is a high proportion of stem frac- tion in the yield, in contrast to cultivars used for feed. Other useful properties for a cultivar are abundant biomass and adaptability to the pre- vailing climate. The variety experiments per- formed in this study showed modest differences in yielding capacity and in the proportion of stem fraction. However, when harvested in spring, the cultivars Barphal 050 and Lara were superior in northern Finland, and also in Laukaa, in mid- Finland, where the snow cover is moderately deep in winter. Jo 0510, Palaton, Lara, and Van- tage were more productive in the trials in west- ern Finland, Jokioinen, Ylistaro and Ruukki. However, Lara was less suitable for fibre pro- duction because of its lower fibre content, asso- ciated with higher mineral content compared with Palaton. Breeding reed canary grass for non- food purposes continues in Finland and Sweden and new cultivars are to be released close to- wards the end of this decade. Cultivation of reed canary grass has started in Finland, and it is now sown on more than 500 hectares. 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Näihin lähtökohtiin perustuen aloitettiin vuonna 1990 tutkimus, jonka tarkoituksena oli kehit- tää menetelmä, jolla saataisiin tuotettua suomalaisista peltokasveista koivun veroista lyhytkuituista raaka- ainetta mahdollisimman edullisesti hienopaperin raa- ka-aineeksi. Samalla oli tarkoitus saada elintarvike- tuotannosta vapautuville pelloille uutta käyttöä. Tässä väitöskirjassa esitetyt tulokset ovat Agrokuitututki- muksen kasvintuotanto-osasta vuosilta 1990 ja 1993– 1999. Koska nämä tulokset ovat osa suuremmasta kokonaisuudesta, väitöskirjassa on tarkasteltu myös projektin muiden osatutkimusten sekä ruokohelven kuitukäyttöön läheisesti liittyvien muiden tutkimus- ten tuloksia suhteessa kasvintuotantotukimuksista saatuihin tuloksiin. Tämän tutkimuksen tarkoituksena oli selvittää, voidaanko Suomen peltokasveista löytää sellun raa- ka-aineeksi soveltuvia lajeja, joita voitaisiin tuottaa kilpailukykyiseen hintaan ja onko tuotantotekniikal- la mahdollista vaikuttaa suotuisalla tavalla sellun raa- ka-ainekasvien biomassan tuottoon ja kemialliseen koostumukseen. Tutkimuksen tarkoituksena oli myös laatia kuvaus suurille viljelyaloille tarkoitetusta vil- jelymenetelmästä, joka tuottaisi tarkoitukseen valitus- ta kasvilajista teollisuuden käyttöön mahdollisimman laadukasta, lyhytkuituista raaka-ainetta. Alustava tutkimus käynnistyi vuonna 1990, jol- loin mukana oli 17 kasvilajia. Näistä valittiin edel- leen sellu- ja kivennäisanalyysien perusteella seitse- män kasvilajia viljelyteknisiin tutkimuksiin, joissa selvitettiin kasvien biomassan tuottoa sekä viljelytoi- menpiteiden vaikutusta sellun ja paperin valmistuk- sen kannalta tärkeisiin laatutekijöihin. Vuonna 1993, jolloin vakavasti otettavia ehdokkaita lyhytkuituiseksi sellukasviksi oli enää ruokonata (Festuca arundina- cea Schreb.) ja ruokohelpi (Phalaris arundinacea L.), perustettiin laajoja kenttäkokeita molemmista kasvi- 96 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Saijonkari-Pahkala, K. Non-wood plants as raw material for pulp and paper lajeista. Samaan aikaan tutkimusta laajennettiin kä- sittämään koko tuotantoketju viljelystä paperin val- mistukseen saakka. Tuotantotekniikan vaikutuksia ruokohelven ja ruokonadan biomassasadon määrään, sellun valmis- tuksen kannalta tärkeiden kivennäisaineiden pitoi- suuksiin sekä sellusaantoon ja laatuun tutkittiin eri korjuuaikoina ja käyttäen erilaisia lannoitusmääriä. Kasvilajeista vain ruokohelpi soveltui monivuotisessa viljelyssä korjattavaksi keväällä kuloheinänä, mikä kokeilluista korjuutavoista tuotti sellun valmistukseen parhaiten soveltuvaa raaka-ainetta. Ruokohelpi osoit- tautui myös kestävimmäksi kasvilajiksi, jonka kuiva- ainesadot vakiintuivat ensimmäisen korjuuvuoden jälkeen noin 7–8 tonniksi hehtaarilta. Kun ruokohel- pi korjataan keväällä, kylvöjen väli voi olla jopa kymmenen vuotta. Ruokohelven vuotuiset typpilan- noitusmäärät vaihtelevat 50–100 kg N hehtaarilla. Markkinoilla olevia ruokohelven rehulajikkeita voi- daan käyttää kuidun raaka-aineena ja ne menestyvät aina Pohjois-Suomea myöten. Parhaiten kevätkorjuu- seen soveltuivat Palaton, Lara, Vantage ja Venture lajikkeet. Viljelyn lopettamisen jälkeen ruokohelpi ei jää pellolle rikkakasviksi, jos kasvusto hävitetään glyfosaatilla ja kynnetään syksyllä, ja parina seuraa- vana vuonna viljellään yksivuotisia kasveja esim. kevätviljaa. Heinäkasvien kivennäisaineiden pitoisuudet oli- vat suurempia kuin puuraaka-aineessa, mutta kuitu- pitoisuudet lähes samanlaisia. Ruokohelpiraaka-ai- neen laatuominaisuuksia voitiin parantaa korjaamal- la kasvusto keväällä kuivana kuloheinänä, jolloin sa- don vesipitoisuus on ainoastaan 10–15 %. Sellun val- mistuksessa haitallisten kivennäisaineiden määrää voitiin vähentää käyttämällä ruokohelven keväällä kuloheinänä korjattua satoa, ja edelleen poistamalla kevätkorjatusta materiaalista lehtilavat, jotka sisälsi- vät eniten kivennäisaineita ja vähiten kuitua. Ruoko- helven kasvinosista korsi sisälsi eniten kuitua ja vä- hiten kivennäisaineita ja se soveltuu siten parhaiten sellun valmistukseen. Kun uusi kasvilaji otetaan lyhyessä ajassa laaja- mittaiseen tuotantoon, se vaatii onnistuakseen laajo- ja tutkimuksia, jotka etenevät samaan aikaan koko tuotantoketjussa. Tämän tutkimuksen tulosten käyt- tökelpoisuus ja siten myös tutkimuksen onnistuminen punnitaan tulosten soveltamistilanteessa, kun ruoko- helpeä viljellään suurilla pinta-aloilla ja saatu raaka- aine käytetään sellun valmistukseen. 97 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Appendix 1 98 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Appendix 1 99 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Appendix 1 100 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Appendix 1 101 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Appendix 1 Non-wood plants as raw material for pulp and paper Preface Contents List of abbreviations Glossary of technical terms Non-wood plants as raw material for pulp and paper 1 Introduction 2 Review of relevant literature on papermaking from field crops 3 Objectives and strategy of the study 4 Materials and methods 5 Results 6 Discussion 7 Conclusions 8 References SELOSTUS Appendix