Climatic conditions for crop production in Nordic countries Ame Oddvar Skjelvåg Department ofHorticulture and Crop Sciences, Agricultural University ofNorway, N-1432 As, Norway, e-mail: arne.skjelvag@iph.nlh.no Climate is today a more determinant factor for yield level than it was in the past, when soil fertility was more important. The regional variation in radiation during the growing season in Nordic coun- tries is less than that in temperature conditions. A combined plant growth-related index of these climatic factors accumulated during the growing season decreased from an annual value of 106 at 56°N (odum, East Jutland) to about 90, 60 and 44 at 60°N, 67°N and 70°N, respectively. The differ- ence between coastal areas in Norway and the Finnish interior was either negligible or about 10% in disfavour of the coast at 67°N. When the moisture conditions ofan imaginary pasture crop on a sandy soil were taken into account, the combined accumulated growth index of radiation, temperature and soil moisture was 71 at odum. On the Norwegian coast, the values were 72, 49 and 37, whilst in Finland, up to northeastern Norway, they were 56, 43 and 35 at 60°N, 67°N and 70°N, respectively. Plant production potential may be directly related to the accumulated growth index. Key words: daylength, radiation, soil moisture, temperature ntroduction A crop production system consists, on the one hand, of environmental components: soil, cli- mate, pests and management practices, and on the other, of the plant material. Either of the fac- tors - environment or plant genetic potential - can be the more limiting with respect to yield level (Geisler 1980). The main components are strongly affected by management and breeding. The natural resource base of the environmen- tal component consists of soil and climate. Of these two, the climatic component has assumed an increasingly determinant role in yield forma- tion in recent decades along with the improve- ment in management practices. Before 1940,the average grain yields in three Norwegian regions ranged from 2100 to 2300 kg/ha, being lowest in the southern Oslofjord area (59-60°N), high- est in the Mjpsa region (61°N), and intermedi- ate in Central Norway (63-64°N). In the 1980s, yields generally had doubled, being highest in the south, intermediate in the Mjpsa region and lowest in Central Norway (Strand 1989). The Oslo- fjord region consists of Precambrian or Permian © Agricultural and Food Science in Finland Manuscript received February 1998 149 Vol. 7(1998): 149-160. AGRICULTURAL AND FOOD SCIENCE IN FINLAND bedrock, whilst the soils of the main agricultur- al areas of the other two regions derive from Cambrian and Silurian rocks. Today grain yield is controlled by climatic conditions, whereas formerly it depended more on soil fertility. The interaction between soil and climate is nevertheless still crucial. Pest attacks are great- ly influenced by climatic factors and, to be timely and successful, even modern field operations need favourable weather conditions. A physical geographical regional division based on natural vegetation integrates climatic and edaphic fac- tors (e.g. NU B 1977). The applicability of this division for agronomic purposes is, however, poor because of the high degree of manipulation in agricultural ecosystems. Comprehensive map- ping of land capability based on both soil and climate is still lacking in the Nordic countries. Thus, the methods used for characterising the natural resources for crop production described here are based mainly on climatic criteria. The three main climatic factors determining crop growth and development are the energy flow by radiation, temperature, and the soil moisture supply as related to weather, soil and plant pa- rameters. Photoperiod may also be a critical fac- tor, for perennial crops in particular. Radiation The variation in radiation climate throughout the Nordic countries is considerable due to their great geographic extent from south to north and to regional differences in cloud cover, although, at about the summer solstice, the daily radiation is more or less the same in southernmost and northernmost Norway. Reduced insolation in the north due to the lower elevation of the sun at that time is compensated by a longer photoperi- od. From April to September the variation in to- tal global radiation with latitude may be more than 20% of the average (Fig. 1). During the growing season defined by temperature limits, the differences are less prominent, because the season in the north is more strongly restricted to the period with the highest insolation. The vari- ation from west to east may be of equal magni- tude to that from south to north, as indicated by data on Sweden (Fig. 1). A similar variation is found in all the Nordic countries except Finland (SNP 1992). Within a region, too, the monthly sums ofglobal radiation may differ between sites by as much as 20%, even over short distances (Gjessing 1969). When the aspect and slope of the ground are included, the monthly means of radiation intensity may differ by up to ±15% in the Sognefjord area of Norway (Gjessing 1969). Although the displacement in spectral distri- bution from shorter to longer wavelengths is greater in the north than in southerly locations (Kvifte et al. 1983), the spectral distribution of photosynthetic active radiation and the near in- frared part of the spectrum can probably be omit- Fig. 1. Accumulated insolation, MJm 2 , in Sweden from April to September during an unspecified number of years (Ångström et al. 1974). 150 Seminar in honour of the 100th anniversary ofMTT AGRICULTURAL AND FOOD SCIENCE IN FINLAND AGRICULTURAL AND FOOD SCIENCE IN FINLAND 151 ted from agroclimatic mapping without risks of a serious error. Temperature The normal air temperature during the high sum- mer peak ranges from below 10°C to over 17°C in areas with agricultural production in the Nor- dic countries. Between a coastal area and the interior at the same latitude and altitude sum- mer temperatures may differ by more than 5°C. Temperature level is frequently used to determine the start and end of the growing season. When the passage of 5°C diurnal mean temperature is used as the criterion in both spring and autumn, the duration of the growing season varies from 220 to 120 days, the latter referring to areas with agriculture in northernmost and mountainous regions. The western and eastern transects from south to north in Figure 2 indicate higher peaks in the east, and a slower rise and fall in temperature curves, and a more pronounced north-south gra- dient in the west. Curves based on 30-year stand- ard normals are regular in shape, and so the av- erage temperature conditions of the growing sea- son can be characterised by selecting two month- ly means only (Fig. 3). A higher April tempera- ture indicates an early spring. In Norway, the April temperature is closely correlated with the time of the thaw, and distribution from north to south is seen along the ordinate. July tempera- ture indicates continentality, and distribution from west to east is shown along the abscissa. Figure 3 shows thatFinland, all the way from south to north, is on the continental side of the scatter diagram. Denmark has the highest tem- peratures in both spring and summer. Iceland represents an extreme maritime climate, but an equivalent is found in the Lofoten region of northern Norway. The two countries on the Scan- Fig. 2. Normal air temperature from 1931 to 1960 as 5-day means at certain sites in the Nordic countries. Norwegian data after Bruun (1967); Danish, Icelandic and Swedish data calculated by Fourier series from monthly means (J.E. Olesen, pers. comm.), and Finnish data from monthly means (R. Solantie, pers. comm.), cf, SNP (1992). Vol. 7(1998): 149-160. dinavianpeninsula, Norway and Sweden, partly overlap, northern Sweden partly with Finland, and southern Sweden with Denmark. Thermal- ly, mountainous sites in southern Norway and northern Sweden resemble coastal locations in northern Norway during spring and summer. The larger agricultural areas of the Nordic countries have the climatically most favourable conditions, i.e. higher April and July temperatures. The temperature sum is the climatic index most widely used to characterise the tempera- ture climate for agricultural production. Its ad- vantage is that it combines temperature level and duration of the growing period into a single term. Figure 4 shows that the temperature sum ofFin- land with a 5°C base ranges from 600 to 1300 day degrees. In Denmark, it ranges from ca. 1350 to 1700 day degrees from 1 May to 31 October (Mikkelsen and Olesen 1984). Along a western transect the temperature sum above the same base temperature in Norway ranges from about 550 to 1550 degree days for crop production ar- eas (B. Aune, The Norwegian Meteorological Institute, pers. comm.). Growing conditions have been characterised by means of the temperature sum in various ways in the Nordic countries, and a comprehensive comparison is not possible (SNP 1992). The tem- perature sum, which represents a general char- acterisation omitting other important factors such as radiation, soil moisture regime and specific requirements of individual crops, is a linear ap- proximation of therelationship between temper- ature and the rate of phenological development. It is therefore a useful index ofassessing the ther- mal conditions needed for a seed crop to reach maturity, and as such is widely used (e.g. Strand 1964). However, such a simple index may put typical coastal and inland areas in Norway into the same climatic zone for choice of cereal cul- tivars, even though the climatic conditions for grain production are quite different. Further- Fig. 3. Nordic sites distributed according to monthly mean temperatures of April and July 1931-1960. T Denmark, O Finland, A Iceland, O Norway, • Sweden. (Several pub- lic sources of the Nordic meteorological institutes). Fig. 4. Annual temperature sum in Finland with 5°C asbase temperature and recordings from 1931 to 1960 (Solantie 1976). 152 Seminar in honour of the 100th anniversary ofMTT AGRICULTURAL AND FOOD SCIENCE IN FINLAND more, the assumption of a linear relationship between temperature and rate of phenological development does not always hold, and the base temperature certainly varies with the phenolog- ical phase (Skjelvåg 1981b). An alternative approach can be illustrated by analysing climatic conditions for the phenolog- ical development of annual ryegrass (Lolium multiflorum L. var. westerwoldicum) in Aust- Agder county, Norway. There, the range of tem- perature from sea level to about 1000 m a.s.l. is similar to that from south to north in the whole country. Using daily weather records and start- ing with the first day of snowless ground (Skjelvåg 1987), we were able to calculate the earliest sowing day from weather and soil pa- rameters (Skjelvåg 1986b) and the rate of phe- nological development as a function of diurnal mean temperature (Skjelvåg 1986a), and to de- fine the end of the growing season by the pas- sage of a 6°C diurnal mean temperature for a 7- day period. Series of daily weather records over decades were applied to assess annual variation (Skjelvåg 1986c). On a clay loam at about sea level the number of summers in a 27-year peri- od permitting 4, 3 or only 2 harvests were 4, 17 and 8, respectively. At about 200 m a.5.1., 2 or 3 harvests per year were equally frequent, where- as no more than one harvest per year was ever possible at 920 m a.s.l. For a seed crop, a risk analysis of harvesting conditions should be in- cluded. Decisions under uncertainty are charac- teristic of crop production. More analyses of cli- matic risks of various types should therefore be carried out (e.g. Mukula and Rantanen 1987, Rantanen and Solantie 1987). Daylength Photoperiod varies regularly with season and latitude. From an equal duration ofday and night at the spring equinox, a maximum daylength of about 17 h is reached in southern Denmark and of 24 h at the Arctic Circle and northwards. Dur- ing the growing season, daylength varies from 14 to 24 h at the start and from 9 to 12 h at the end of the period (Fig. 5). An increase in daylength enhances the rate ofphenological development of long-day plants. In old Norwegian cultivars of spring cereals, the degree days requirement from sowing to yellow ripeness was reduced by 3-7% when the cereals were grown at 63°N rather than 60°N (Eikeland 1936). Since photoperiod affects the rate of de- velopment only before heading (Bleken and Skjelvåg 1986), the relative reduction in day degrees must have been about twice this figure during that phase. Such a reduction in thermal requirement contributes to successful cereal pro- duction in cool areas of the north. From phytotron experiments we know that a long photoperiod stimulates the dry matter pro- duction of grass seedlings of Nordic ecotypes (Heide et al. 1985). This stimulation compen- sates for a reduction in temperature of several degrees centigrade (Heide 1985). However, we Fig. 5. Photothermogram with corresponding 5-day air tem- perature averages (1931-1960 normals) and photoperiod including civil twilight to -4° at one location in Denmark, and at two locations in Norway. Each point represents a 5- day period, the right-hand branches of the curves describe the period from the passage of the 5°C diurnal mean in spring to the summer solstice, and the left-hand ones the remaining part of summer and autumn. 153 Vol. 7 (1998): 149-160. AGRICULTURAL AND FOOD SCIENCE IN FINLAND still lack proof as to whether this effect mani- fests itself in a crop stand (Hay 1990). Growth cessation ofperennial crops is strong- ly affected by photoperiod. We can assume that elongation growth has to stop early enough to ensure the accumulation of reserve carbohydrates before photosynthesis becomes negligible. Clear- ly an ecotype adapted to northern conditions must stop growing at a longer photoperiod than one of southern origin (Fig. 5). This phenome- non is recognised in grassland production. Foss (1968) grew 14 Nordic timothy ecotypes origi- nating from approximately 59°N to 69°N in the same field at 63°N. Regrowth during the period 14 July to 30 September decreased linearly with latitude of origin, r = -0.91. This response to photoperiod is favourably exploited in ensuring winter hardiness by using northern grass culti- vars at high-altitude areas farther south (Baads- haug 1974). Most perennial grasses of northern origin have a dual requirement for induction to flower- ing (Heide 1994). Primary induction is brought about by low temperature and/or short days, and secondary induction by long days. Seed yields have been poor for North Norwegian ecotypes of smooth meadow grass (Poa pratensis L.) transferred to Denmark for seedproduction, and have even failed when transferred to the Nether- lands and Canada (Heide 1980). Arctic ecotypes attain primary induction at longer days than southern ones. Thus, they will reach an early and advanced stage of flower development when grown in the long autumns of southern latitudes, making the primorida vulnerable to insect and winter damage, particularly in years and regions with unstable winter weather and recurrent freez- ing and thawing. Water supply Within the driest areas of the Nordic countries the mean annual precipitation is only 200-250 mm, but in the wettest areas it exceeds 4000 mm/yr. Large areas in the northeast get less than 500 mm/yr. More than 1000 mm/yr falls in south- ernmost Norway, to the west of the mountain range up to 69°N, and in the south of Iceland (Spmme 1968). Annual evaporation is estimat- ed to vary from about 200 mm in the north to 600 mm in the south of the Nordic countries (Johannessen 1970, Einarsson 1972). However, evaporation is most intense during the growing season, and a precipitation deficit is common in the larger agricultural areas. The main factors determining the natural water supply to plants are the amount and distri- bution of rainfall, soil moisture capacity, evapo- ration and the development of plant organs above and below the ground. Thus, soil and plant de- velopment assume as great importance as clima- tic variablesfor determining water balance, and this creates problems in defining a geographical index based on soil moisture characteristics. Simplified indices such as the potential pre- cipitation deficit (PPD) have therefore been es- tablished. PPD is defined as the difference be- tween potential evapotranspiration and rainfall during a specified period of time, disregarding soil moisture capacity and plant development. Utaaker (1979) calculated PPD for May to Au- gust 1966for a 160-km transect along the Sogne- fjord and found a variation from a deficit of 150 mm to a surplus of 250 mm. Probably the whole agricultural area of the Nordic countries falls within this range. In Sweden, from June to Au- gust 1951-1980, PPD was estimated to range from more than 100 mm in the southeast to a surplus of 100 to 150 mm locally in the south- west. The larger agricultural areas had a deficit (Eriksson 1986). More specific estimates have been made in Denmark and Finland. Actual evaporation from grassland in Finland was estimated to range from 150 to 350 mm/yr (Fig. 6). Based on weather records for 1931-1960 and for the period from thaw to the end ofJuly, a deficit of 120 mm was estimated for southwestern Finland, and a sur- plus of about 40 mm for the northernmost part of the country. In Denmark, detailed soil map information has been combined with weatherand 154 Seminar in honour of the lOOth anniversary ofMTT AGRICULTURAL AND FOOD SCIENCE IN FINLAND plant data to estimate irrigation needs.For spring barley the average need varied from less than 40 to up to 80 mm per season (Madsen et al. 1987). Other elements Several other factors besides the four climatic ones discussed above also influence conditions for crop production; one of these is overwinter- ing of perennial and biennial crops. It has been estimated that annual losses due to winter dam- age to grassland and biennial crops in the Nor- dic countries total NOK 900 million (Vinterher- dighet 1988). The climatic influence onoverwin- tering starts in the preceding summer and autumn with growth cessation, accumulation of reserves and hardening. It continues during the winter with dehardening, rehardening, the impact of frost, the creation of conditions conducive to water and ice damage, attacks by wintering fun- gi, and a general exhaustion of reserves with time. The situation varies markedly from region to region and is counteracted by both improved management practices and breeding for winter hardiness. A brief description of the predomi- nant types of winter damage in various parts of the Nordic countries is given elsewhere (SNP 1992). Internationally, attempts have been made to quantify relationships between climate and pests and diseases (e.g. Mischenko 1984); Nor- dic attempts in this field seem, however, to be lacking. Various operations in crop production are best carried out when it is not raining. The cost due to suboptimal timing ofsuch operations is a func- tion of weather, crop and technical equipment. Danish agrometeorologists have calculated the number of possible harvesting hours for spring barley in 1953-1980 for a range of required moisture contents of the grain (Olesen and Mikkelsen 1985a, 1985b). Agroclimatic mapping of this type emphasises the need for a high reso- lution level of weather observations; these are, however, still very scarce (SNP 1992). Fig. 6. Upper: Actual evaporation from grassland, mm/yr (after Solantie 1975, 1976). Lower; Difference between precipitation and actual evaporation of grassland from thaw to the end of July, mm (after Solantie 1987). Both: Based on weather records 1931-1960. 155 Vol. 7 (1998): 149-160. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Growth indices Characterisation of the climatic conditions for crop growth by means of a growth index com- bining radiation, temperature and soil moisture was proposed for Nordic conditions by Angus et al. (1980), and applied on a global scale by Hutchinson et al. (1992). A grassland model de- veloped by a Swedish team has been used for some Nordic locations. The start and end of the growing season was set to the passage of a diur- nal mean temperature of 5°C for a 7-day period. Radiation and temperature indices were calcu- lated according to Torssell and Kornher (1983), whilst a soil moisture index was estimated ac- cording to a model of Ritchie (1972) and modi- fied by Skjelvåg (1981a). The root zone field capacity of plant available water was set to 90 mm, which was assumed to be the available soil moisture content at the start of the growing sea- son. The phase I soil evaporation of the Ritchie model was set to 4.0 mm, and its a-value, which determines maximum soil evaporation in phase 11, to 3.5 mm/day05 , representing a sandy soil. The fraction ofplant available soil moisture read- ily available for plants was set to 20%. Leaf area index was set to 1.4 at growth start, allowed to increase to 2.0, and thereafter kept constant throughout the rest of the season. Long series of weather records were applied (Table 1). Poten- tial evapotranspiration was estimated according to Penman (1956) for Norwegian stations and according to a modified Penman equation for Denmark (Mikkelsen and Olesen 1991). For Finnish stations, Class A pan evaporation was adjusted by a factor of 1.06 according to Heldal (1969). The model estimates give indices of radia- tion related to plant growth (RI), temperature (TI) and soil moisture (SMI). These indices show curvilinear relationships between plant growth and radiation, temperature and availability ofsoil moisture to the crop, respectively. All the indi- ces were computed on a day-by-day basis using annual series of daily weather recordings. They have a valueof 0.0 when individual factors limit plant growth absolutely, and 1.0 when they are at their optimal levels. The combined growth index (GI) was definedas: GI = RI*TI*SMI. Soil moisture may be controlled by irrigation, but RI and TI cannot be controlled under field condi- tions. The combined effect of these two was de- fined as: RTI = RI*TI. All derived means or sums presented in Tables 1 to 3 are based on the daily values of long term series. Taking East Jutland (odum) as a reference site, the energy supply as characterised by RTI decreases northwards (Table 1). Along the coast ofNorway it decreases northwards in all months, but only slightly from 67°N to 70°N in July. Along a northeastern transect from Denmark through Finland to Pasvik in Norway, RTI re- mains high in June and July up to higher lati- tudes than it does in the west. At the beginning and end of the growing season, there is less dif- ference between western and eastern transects. The same difference between coastal and inland areas is seen by comparing locationsat about the same latitude, and even in May at about 60°N. In July, RTI attains about three-quarters of its maximum value of 1.0 in Denmark, southern Finland and southeastern Norway, but it is re- duced by one-third to about half of the maxi- mum value in the far north (Table 1). Earlier and later in the season the reduction is greater due to the shorter growing season in the north. Thus, the figures show that energy and thermal con- straints on crop production generally increase northwards and westwards. However, when we consider the total production potential as ex- pressed by GI, soil moisture conditions modify the above picture considerably. The difference between GI and RTI (Table 2) shows that the soil moisture deficit reduces crop production poten- tial more in the south than it does in the north, and more in the east than in the west (Table 2). Ley yields in Sweden, simulated by the same grassland model, though with a different soil moisture routine, agreed well with independent field observations, both as averages and as stand- ard deviations (Fagerberg 1991). Thus, GI may be an appropriate indicator of dry matter pro- duction potential. In the case of Denmark, with 156 Seminar in honour of the 100th anniversary ofMTT AGRICULTURAL AND FOOD SCIENCE IN FINLAND Table 1. Long-term daily means of the combined radiation and temperature index (RTI) multiplied by 100, at Nordic locations. Contributing indices only for days with diurnalmean temperature above 5°C, after passing 5°C fora 7-day period in spring and until passage of the same temperature in autumn. Month Location °N Years 3 4 5 6 7 8 9 10 11 odum, DK 56.3 1961-95 2 14 53 73 74 68 43 16 2 Sola, N 58.9 1957-91 1 11 43 62 65 61 37 15 2 Ås, N 59.7 1970-90 6 50 71 73 62 30 Helsinki, F 60.3 1971-90 4 47 70 76 62 28 5 BodO.N 67.3 1957-92 2 22 46 51 45 19 3 Apukka, F 66.6 1970-90 20 60 69 46 12 1 Tromso, N 69.7 1951-91 8 35 49 37 10 1 Pasvik, N 69.1 1957-91 8 41 52 38 9 odum at 56°N as a reference site, Table 3 indi- cates that the yield potential of an irrigated crop might be about 85%, 60% and 44% of that at odum at about 60°N, 67°N and 70°N, respec- tively. The difference between the coast and the interior at comparable latitudes seemed to be greatest at 67°N, between Bodo and Rovaniemi (Apukka). After reduction for soil moisture def- icit, the relative values of the accumulated GI at the same three latitudes along the coast of Nor- way became 101%, 69% and 52%, respectively, whilst in Finland and up to Pasvik in Norway the accumulated GI was 79%, 61% and 49% of the Danish reference. The bulk of the big differ- ence between west and east at about 60°N came between southeastern Norway and Helsinki, be- cause Ås, at about the same longitude as odum, attained 94% of the reference sum. At 67°N the advantage of Rovaniemi over Bodo under irri- gated conditions, RTI, turned into a disadvan- tage of similar magnitude under rainfed condi- tions, GI. In the far north, a similar, but much less pronounced, change appeared between coastal Tromsp and inlandPasvik. Table 2. Soil moisture deficit as long-term difference between the combined index ofradiation and temper- ature (RTI) and the combined growth index (GI), both multiplied by 100, ((RTI-GI)IOO). Contributing indices only for days with diurnal mean temperature above 5°C, after passing 5°C for a 7-day period in spring and until passage of the same temperature in autumn. Month Location °N Years 5 6 7 8 9 10 odum, DK 56.3 1961-95 Sola, N 58.9 1957-91 Ås, N 59.7 1970-90 Helsinki, F 60.3 1971-90 Bodo, N 67.3 1957-92 Apukka, F 66.6 1970-90 Tromsp, N 69.7 1951-91 Pasvik, N 69.1 1957-9169.1 1957-91 12 30 34 36 9 I 9 20 20 13 2 11 27 25 17 3 13 40 36 18 3 2 12 8 6 1 2 20 30 13 1 4 9 5 1 7 16 8 1 157 Vol. 7(1998): 149-160. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Table 3. Accumulated long-term annual indices over the growing season, defined as days between passage of a 7-day average of 5°C air temperature in spring and autumn, for a reference station at 56°N (odum, Denmark), and at 60°N (Ås, Norway). ‘West’ is the coast of Norway, and ‘East’ is Finland and Norway’s Pasvik, RTI = combined radiation and temperature index. GI = combined radiation, temperature and soil moisture index. °N RTI GI approx. West odum/As East West odum/As East 56 106 71 60 91 89 90 72 67 56 67 57 63 49 43 70 43 45 37 35 Table 4. Number of cultivars of spring barley (Hordeum vulgäre L.) and timothy (Phleum pratense L.) on national lists of recommended cultivars for 1997 in the Nordic countries, according to three types oforigin: ‘National’ = bred in the country, ‘Other Nordic’ =bred in another Nordic country, ‘Others’ = bred in other countries. National OtherNordic Others Sum Country Barley Timothy Barley Timothy Barley Timothy Barley Timothy Denmark 9 1 8 1 32 1 49 3 Finland 12 9 8 5 1 0 21 14 Iceland 02 83 00 85 Norway 5 4 4 1 1 0 10 5 Sweden 21 7 3 1 15 1 39 9 The above assessments by climatic indices refer to a hypothetical crop that might be asso- ciated with a pasture with a relatively low leaf area index. The full interaction of weather with a variety of crops was not explored. The origin of cultivars on national recommended lists may be taken as an indication of the constraints on the choice of suitable plant material in the dif- ferent Nordic countries (Helgadottir 1996, Med- delelser fra sortsafprpvningen 1997, Statens landbrukstilsyn 1997, Statens Växtsortsnämnd 1997, Växtsortsnämnden 1997). On the Danish list of spring barley cultivars, more than 60% were bred outside the Nordic countries, and on the Swedish list about 40%; the other countries each had one or none in this category (Table 4). For perennial timothy, only one out of three cul- tivars originated from other European countries on the Danish list and one out of nine on the Swedish list. In the other three countries only national cultivars or those from other Nordic countries were officially recommended for use. If we assume that the official performance test- ing of cultivars is an objective way of screening suitable plant material, these statistics clearly show the need for locally adapted plant material in marginal crop production areas. Assessment of production potential has to combine climatic parameters with soil data. Spe- cific requirements ofindividual crops make crop growth models useful tools in expressing pro- duction potential in agronomically meaningful ways (SNP 1992). The climatic constraints on crop production will be properly expressed only when climatic information is combined with soil data, the specific requirements of individual crops and with the relevant management prac- tices. Modern information technology offers great possibilities in analyses of crop produc- tion potential and its variation geographically as 158 Seminar in honour of the 100thanniversary ofMTT AGRICULTURAL AND FOOD SCIENCE IN FINLAND well as in time. A wide range of applications can be indicated from land capability studies, ad- ministrative duties, strategic and tactical plan- ning in agriculture and farm operational purposes to teaching. Acknowledgements. The author is indebted to Mr Endre Skaar, Mr Jorgen E. Olesen and Dr Reijo Solantie for pro- viding the weather data. The insightful comments on the manuscript from Dr Ole Hans Baadshaug are gratefully acknowledged. References Angstrom, A., Liljequist, G.H. & Wallén, C.C. 1974. Sver- iges klimat. 3:e uppl. Generalstabens litografiske anstalts förlag, Stockholm. 188 p. Appendix. Angus, J.F., Kornher, A. & Torssell, B.W.R. 1980. A sys- tems approach to estimation of Swedish ley produc- tion. Progress report 1979/80. Rapport 85. Institutio- nen för växtodlingslära, Sveriges lantbruksuniversitet. 29 p. Baadshaug, O.H. 1974. Jordbruksmessig utnytting av fjellfrakfene. En översikt over norske undersokelser. Forskning og torsok i landbruket 25, 4. Supplements- hefte. 53 p. Bleken, M.A. & Skjelvåg, A.O. 1986. The phenological development of oat (Avena sativa L.) cultivars as af- fected by temperature and photoperiod. Acta Agri- cultures Scandinavica 36: 353-365. Bruun, 1.1967, Standard normals 1931-60 of the air tem- perature in Norway. Det norske meteorologiske in- stitute Oslo. 270 p. Eikeland, H.J. 1936. Forsok med vårkveite, havre og bygg på forsoksgarden Voll og på 43 gardsfelt i Trondelag og More og Romsdal i åra 1926-1936. Melding frå Statens forsoksgard Voll. Landbruksdirektorens års- melding, tillegg H: 8-72. Einarsson, M.A. 1972. Evaporation and potential eva- potranspiration in Iceland. Vedurstofa Islands. Rey- kjavik. 27 p. Eriksson, B. 1986. Nederbörds och humiditetsklimatet i Sverige under vegetationsperioden. SMHI Rapport- er, Meteorologi och klimatologi (RMK) 46. 73 p. Fagerberg, B. 1991. The effect of weather fluctuations on simulated ley growth in Sweden. Swedish Jour- nal of AgriculturalResearch 21: 95-105. Foss, S. 1968. Vekstrytme hos timoteisorter. Forskning for forsok i landbruket 19: 487-518. Geisler, G. 1980. Pflanzenbau. Verlag Paul Parey, Berlin & Hamburg. 480 p. Gjessing, Y.T. 1969. Local climates and growth climate of the Sognefjord region, the radiation climates. Me- teorologiske annaler 5: 395-428. Hay, R.K.M. 1990. The influence of photoperiod on the dry matter production of grasses and cereals. Tans- ley Reviews No 26. New Phytologist 116: 233-254. Heide O.M. 1980. Studies on flowering in Poa pratensis L. ecotypes and cultivars. Metdinger fra Norges land- brukshogskole 59, 14. 27 p. - 1985. Physiological aspects of climatic adaptation in plants with special reference to high-latitude envi- ronments. In: Kaurin, A. et al. (eds.). Plant growth in the North. Norwegian University Press, Oslo. p. 1- 22. - 1994. Control of flowering and reproduction in tem- perate grasses. New Phytologist 128: 347-362. - , Hay, R.K.M. & Baugerod, H. 1985. Specific daylength effects on leaf growth and dry matter production in high-latitude grasses. Annals ofBotany 55: 579-586. Heldal, B. 1969. Evaporation from different evaporation pans in relation to meteorological conditions. Met- dinger fra Norges landbrukshogskole 48, 25. 42 p. Helgadottir, A. (ed.) 1996. Nytjuplöntur ä Islandi 1997. Rannsöknastofnun landbunadarins. 15p. Hutchinson, MR, Nix, H.A. & McMahon, J.P. 1992. Cli- mate constraints on cropping systems. In: Pearson, C.J. (ed.). Field Crop Ecosystems, p. 37-58. (Vol. 18 of Goodall, D.W. (ed.). Ecosystems of the World). Johannessen, T.W. 1970.The climate of Scandinavia. In: Wallén, C.C. Climates of Northern and Western Eu- rope. World Survey of Climatology. Volume 5. p. 23- 80. Kvifte, G., Hegg, K. & Hansen, V. 1983. Spectral distri- bution of solar radiation in the Nordic countries. Jour- nal ofClimate and AppliedMeteorology22:143-152. Madsen, H.8., Holst, K.A. & Mikkelsen, S.A. 1987. The use of EC-soil map in modelling and mapping the root zone capacity and irrigation need. A case study from Denmark. EC- Workshop on computerization of land use data for agricultural and environmental plan- ning, 20-22 May 1987, Pisa, Italy. 14 p. Meddelelser fra sortsafprovningen 1997. Official sorts- liste. Meddelelser fra sortsafprovningen 16. Saernum- mer april 1997. 73 p. Mikkelsen, H.E. & Olesen, J.E. 1991. Sammenligning af metoder til bestemmelsen af potentiel vandfordamp- ning. Tidsskrift for Planteavls Specialserie. Beretning nr. S 2157-1991. 67 p. Mikkelsen, S.A. & Olesen, J.E. 1984. Computer-aided mapping of growing degree days for Denmark, cal- culated from monthly temperature normals. Acta Ag- ricultures Scandinavica 34: 330-338. Mischenko, Z.A, 1984. Agroclimatic mapping of the con- tinents. CAgM Report No 23. World Meteorological Organization, Agricultural Meteorology. 109 p. Mukula, J. & Rantanen, O, 1987. Climatic risks to the yield and quality of field crops in Finland. I. Basic facts about Finnish field crops production. Annates Agriculturae Fenniae 26: 1-18. NU B 1977.Naturgeografisk regionindelningav Norden. 159 Vol. 7(1998): 149-160. AGRICULTURAL AND FOOD SCIENCE IN FINLAND NU B 1977:32. Nordisk Ministerråd, Stockholm. 7:32. Olesen, J.E. & Mikkelsen, S.A. 1985a. A meteorological model for calculating the moisture content of ripe spring barley. Part I. Model description. Acta Agricul- tures Scandinavica 35: 361-368. - & Mikkelsen, S.A. 1985b. Ameteorological model for calculating the moisture content of ripe spring bar- ley. Part 11. Model results. Acta Agricultures Scandi- navica 35: 369-374. Penman, H.L. 1956. Evaporation: an introductory survey. Netherlands Journal ofAgricultural Science 4: 9-29. Rantanen, O. & Solantie, R. 1987. Climatic risks to the yield and quality of field crops in Finland. 11. Cultiva- tion zones and sub-divisions. Annates Agriculturae Fenniae 26: 19-37. Ritchie, J.T. 1972. Model for predicting evaporation from a row crop with incomplete cover. Water Resources ReserachS: 1204-1213. Skjelvåg, A.0.1981a. Experimental and statistical meth- ods of plant experiments used in an agroclimatic in- vestigation in Aust-Agder, Norway. Acta Agriculturae Scandinavica 31: 343-357. -1981b. Effects of climatic factors on the growth and development of the field bean (Vida Faba L. var. minor) 11. Phenological development in outdoor ex- periments. Acta Agriculturae Scandinavica 31: 372- 281. -1986a. Temperatur og fenologisk utvikling hos eitt- årig raigras. Forskning og forsok i landbruket 37: 219-224. -1986b. Utrekning av forste sådag ved vérobserva- sjonar. Forskning og forsok i landbruket37: 295-301. - 1986c. Fenologisk utvikling hos eittårig raigras i Aust- Agder. Forskning og forsok i landbruket 37: 303-311. - 1987. Forste berrmarksdag om våren i Aust-Agder, Norsk tandbruksforsking 1: 215-223. SNR 1992. Agroklimatisk karflegging av Norden. Skrifter och rapporter nr. 5. Samnordisk plantetoredling. 97 p. Solantie, R. 1975. Haihdunnasta Suomessa. In: Ylinie- mi, J. (ed.). Geofysiikanpäivät, Oulu 26.-27.5.1975. p. 195-202. - 1976. Järvien vaikutus lämpötilan mesoskaala-ana- lyysiin Suomessa. Ilmatieteen Laitoksen Tiedonan- toja 30. 72 p. - 1987. The difference between precipitation and evap- oration on cultivated areas from the disappearance of snow to the end of July 1931-1960. In: Atlas of Finland, folio 131 (Climate) 19n. National Board of Survey & Geographical Society of Finland. Somme, A. (ed.) 1968. A Geography of Norden. J.W. Cappelens Forlag, Oslo. 343 p. Appendix Statens landbrukstilsyn 1997. Offisiell sortsliste 1997/98. 20 p. Statens Växtsortsnämnd 1997. Sortslista 1997. Medde- landen från Statens Växtsortsnämnd 2/1997. 20 p. Strand, E. 1964. Dyrkingssoner for jordbruksvekster i Norge. Metdinger fra Norges landbrukshogskole43, 9. 16 p. - 1989. Resultater fra jord- og plantekulturforskningen, korn. In: Den gronne evotusjon. Landbruksforlaget, Oslo. p. 144-154, Torssell, B.W.R. & Kornher, A. 1983. Validation of a yield prediction model for temporary grasslands. Swedish Journal ofAgriculturalResearch 13: 125-135. Utaaker, K. 1979. Lokal- og vekstklima i Sogn. Forsk- ning og forsek i landbruket 30: 113-204. Växtsortsnämnden 1997. Meddelanden från Växtsorts- nämnden 3/1997. 23 p. Vinterherdighet 1988. Vinterherdighet i nordisk vekstfor- edling. Nordisk Ministerråd (Nord. 1988:84). SNP-pub- likation 19. 48 p. Appendix. SELOSTUS Kasvintuotannon ilmasto-olosuhteet Pohjoismaissa Arne Oddvar Skjelvåg Agricultural University ofNorway, Norja Ilmasto vaikuttaa nykyään satoon oleellisesti. Sen si- jaan ennen maaperän viljavuus rajoitti satoa ilmas- toa enemmän. Pohjoismaissa säteily vaihtelee alueel- lisesti vähemmän kuin lämpötila kasvukauden aika- na. Kasvukauden aikana mitatuista säteilystä ja läm- pötilasta voidaan laskea kasvin kasvua kuvaava ku- muloituva indeksiluku. Tämä vuotuinen kasvuindek- si saa 56. pohjoisella leveysasteella (odum, Länsi- Jyllanti) arvon 106 ja pienenee arvoihin 90, 60 ja 44 siirryttäessä pohjoiseen 60., 67. ja 70. leveysasteille. Norjan rannikolla ja Suomen sisämaassa 67. leveys- asteella mitattujen kasvuindeksien ero oli hyvin pie- ni tai vain noin 10 % Suomen sisämaan eduksi. Kun kasvuindeksiä laskettaessa otettiin huomioon myös kuvitteellisen hietamaalla viljellyn laitumen kosteus- olot, saatiin säteilyä, lämpötilaa ja kosteusoloja ku- vaavan kasvuindeksin summaksi odumissa 71. Nor- jan rannikolla 60., 67. ja 70. leveysasteilla lasketut arvot olivat 72, 49 ja 37, kun taas Suomessa vastaa- villa leveysasteilla indeksit olivat 56, 43 ja 35. Kas- vintuotannon potentiaalia voitaneen suoraan arvioi- da kumuloidun kasvuindeksin avulla. 160 Seminar in honour of the 100th anniversary ofMTT AGRICULTURAL AND FOOD SCIENCE IN FINLAND