Vol 4:479-494. Effects of plant species and harvesting system on grassland production in northern Finland Oiva Nissinen Agricultural Research Centre ofFinland, Lapland Research Station, Tutkijantie 28, Apukka, FIN-96900 Saarenkylä Finland Heikki Hakkola Agricultural Research Centre ofFinland, North Ostrobothnia Research Station The dry matter yields and forage quality of seven grassland plant species and mixed stands which included three cutting regimes (pasture 4-5 cuts, silage 2-3 cuts, hay and aftermath) were studied at two locations in northern Finland, Ruukki (64°40’N) and Rovaniemi (66° 35’N). Increased cutting frequency lowered the total dry matter yields of all plant species. Production of timothy (Phleum pratense L.) and smooth brome grass (Bromus inermis L.) swards was significantly reduced by tak- ing four or five cuts instead of one or two cuts. Meadow fescue (Festuca pratensis Huds.) and mead- ow grass (Poa pratensis L.) showed only a minor interaction with harvesting regimes and were less affected by the cutting frequency. The increased cutting frequency raised the crude protein content, this causing the highest protein yields despite the smaller dry matter yields. The inclusion of red clover in seed mixtures had a favourable effect on the crude protein content of grass swards. Stands of sown plants decreased and the proportion of weeds in yields increased with time, reflecting the suitability of plant species to various cutting regimes. Meadow fescue and meadow grass with rapid regrowth had a positive effect on sward density and also caused less invasion of weeds when the cutting frequency was increased. Key words: cutting frequency, dry matter, forage quality, botanical composition, Phleum pratense L., Festuca pratensis Huds., Poa pratensis L., Bromus inermis L., Trifolium pratense L. ntroduction Agriculture in northern Finland relies heavily on livestock, and nearly 80% of the cultivated area is used for growing grass forage, i.e. hay, silage, and pasture. The plants best suited for cultiva- tion under northern conditions are grasses with abundant vegetative growth, as they grow well in a cool climate and can benefit from the long day (Landström 1989). The production of grass- land plants is, however, impaired and the number of harvests reduced by the shortness of the grow- ing season (Pulli 1982). Moreover the most win- terhardy northern varieties grow very rapidly in the middle of the summer, but very slowly in late summer. On the other hand, the number of cuts is determined by the time of the last cut. This has to be chosen to ensure that the gathering of food reserves and hardening can take place be- © Agricultural Science in Finland Manuscript received March 1995 479 AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=Ax9u7dfmN_3pmfj0.zQvjAciBmaLvd1OQfgJ9Eg.6g15cSj7xZBzY9wX5eL0DAWkA1NM6qkO2JboM2gRTOYOjQ0JXrAgphLdjeSdCTyLOjLnTzyIuifLC0SGHAje0_p0zvfy5tz-4PCA5Y1WtTvQWD6udREau2FHUWMlySAy2HVFPNa0RYVGgEQc3D0YH_aULVQHe3zO4JHjzCU6Pvfa1lO-ngDqKwiEFz2jrT956WQAgKaaIaZmxK26h8mANpAzZtaix64p-PGZpCONkvKgPf7PtN7SPOJ9GtUd_3YwWSoGBl1E6kDVCF6S2mftDvZV3xo fore the onset of the long winter (Hakkola et al. 1987). As the time of harvest is linked to the development stage of the stands, some sort of aftermath crop is also harvested in northernmost Finland. There is demand for good-quality grass for- age for both summer and winter feeding. The most important factor influencing total yields is cutting frequency. Advanced mechanization in modern grassland management for silage-mak- ing has resulted in the use of intensive cutting systems. In northern Finland, however, this type of management has caused problems to grass- land yields and the viability of some plant spe- cies. In northern Finland, the straw formation of plants and the sharp increase in dry matter con- tent in early summer cause rapid changes in for- age quality. Fibrousness increases, and the crude protein content and digestibility decrease (Pulli 1980, Huokuna and Hakkola 1984). On the other hand, low temperatures reduce the fibrousness of the plants in the north. At the same morpho- logical development stage, plants in the north have better digestibility than those in the south (Deinum et al. 1981). In the autumn, stands are leafier and changes occur more slowly. Strong straw formation and slow regrowth are typical of timothy {Phleum pratense L.) and smooth brome grass (Bromus inermis L.). Straw formation in meadow fescue (Festuca pratensis Huds.) and meadow grass (Poa prat- ensis L.) is less strong and regrowth is better. Due to its better regrowth ability, meadow fes- cue thrives better than timothy in pasture and silage swards (Järvi 1976, Grönneröd 1988). Meadow grass, too endures many harvests dur- ing the growing period better than timothy (Grönneröd 1972, Landström 1978). Meadow grass has also had a higher yielding regrowth than timothy (Mason and Lachance 1983). Smooth brome grass has been found to thrive even more poorly than timothy in pasture and silage swards (Grönneröd 1972, Järvi 1982), whereas in hay swards, it has given high yields. The total yield ofa mixture oftimothy andmeadow fescue is often higher than that of pure stands of either plant species alone (Raininko 1968, Hakkola 1988, Jorgensen et al. 1994). Under variable growth and wintering conditions, a mixed sward also tends to be more reliable for cultivation than a pure stand (Nissinen and Hak- kola 1989, Jorgensen et al. 1994). Owing to its good resistance to frost and ice encasement, timothy is most winterhardy in the south and on the coast. The winterhardiness of meadow fescue, which withstands snow scald (Sclerotinia borealis) better than timothy, im- proves the farther north it is cultivated (Land- ström 1978, Nissinen and Salonen 1972,Årsvoll 1977). In second-year leys, a rapid increase in the proportion of meadow fescue at the expense of timothy has been reported in mixtures of tim- othy and meadow fescue (Raininko 1968, Hag- sand and Landström 1984, Nissinen and Hakko- la 1989, Jorgensen et al. 1994). The yield of meadow grass has not markedly decreased with an increase in age (Landström 1978, Hagsand and Landström 1984). According to Andersson (1988), meadow grass is best suited for long- duration pasture swards, and the farther north the better. Moreover, the yield of smooth brome grass has improved with the increasing age of the sward, and thus it is suitable for long-dura- tion hay swards (Järvi 1976). Since red clover (Trifolium pratense L.) is not very permanent, the yield of a mixed sward containing clover di- minishes more rapidly than that of pure grass mixtures (Hagsand and Landström 1984, Huoku- na et al. 1985). The protein content of meadow fescue is higher than that of timothy at the same develop- mental stage and at the same harvesting time (Salo et al. 1975). As, however, the yield of meadow fescue is often higher than that of tim- othy harvested at the same time, the protein con- tent of the yield may be lower in meadow fescue than in timothy. The crude protein content is higher in meadow grass than in timothy (Land- ström 1978, Hole 1985). Many studies have fur- ther shown that the protein content of smooth brome grass is higher than that of timothy at the same development stage, harvesting time and yield level (Olsen 1978, Järvi 1982). Red clover 480 AGRICULTURAL SCIENCE IN FINLAND Nissinen, O. & Hakkola, H.: Effects ofcultivation technique on grassland production Vol. 4: 479^94. increases the crude protein content of mixtures. According to the findings of Andersson (1986, 1989), the nitrogen compensating effect of red clover on protein content is greater than the ef- fect on the dry matter yield. In mixtures of plant species, meadow fescue has been found to increase the fibre content ow- ing to its earliness and red clover to reduce it (Hagsand and Landström 1984, Olsen 1978, Åman and Lindgren 1983). The fibre content of meadow grass is higher than that of timothy. Also, smooth brome grass has been found to contain more fibre in an early harvest than tim- othy and meadow fescue, but by the hay stage the fibrousness of timothy may be higher (Järvi 1982, Åman and Lindgren 1983). According to Olsen (1978), meadowfescue is more digestible than timothy when harvested at the same time. Correspondingly, timothy has been found to have better digestibility than meadow grass up to the flowering stage (Mason and Lachance 1983). Like meadow fescue, red clover has also im- proved the digestibility of plant species mixtures (Frankow-Lindberg 1989). In northern Finland, grass forage accounts for almost 60% of the feed units used per milk cow, and thus grassland production is of very great economic importance to cattle farms. The aim of this trial was to investigate the effect of the harvesting system and cutting frequency on the yield and quality of different grassland plants in Table 1. Plant species, varieties, seed mixtures and seed rates used in the trial. Plant Variety Seed rate kg/ha Timothy Iki 20 Meadow fescue Boris 25 Meadow grass Jo 0011 20 Smooth brome grass Kesto 30 Timothy/red clover Iki/Bjursele 15/5 Timothy/meadow fescue Iki/Boris 13/13 Timothy/meadow fescue/ Iki/Boris/ red clover Bjursele 10/10/5 northern Finland. In the field experiments, the superiority and suitability of the most important grass species and mixtures of plant species in pasture, silage and hay swards were compared. The main topics of interest were dry matter yield, forage quality and the persistence ofa sown plant species when different cutting frequencies were used in forage management under the conditions of a short growing season and low temperature sum. Material and methods The trial was carried out during 1987-1992 at the Agricultural Research Centre of Finland’s North Ostrobothnia Research Station in Ruukki (64° 40’N) and Lapland Research Station in Ro- vaniemi (66° 35’N). The field experiments were set up using a split-plot method, with threeharvesting systems - pasture, silage and hay - as the main plots. Plant species and their mixtures were as the split plots. There were four replicates. The species, seeding and nitrogen rates used in the trial are shown in Tables 1 and 2. In Ruukki, the soil used was medium fine sand, pH 6.0, Ca 903, K 51, Pl 5 and Mg 42 mg/ 1. In Rovaniemi, the soil was fine sandy till, pH 5.95, Ca 1254, K 118, P 13 and Mg 165 mg/1. The ground-cover percentage of the plot was evaluated visually in autumn and spring to re- veal winter damage. Before harvesting, the heights of stands were measured and the matur- ing phase was evaluated on a scale of 0-100% (100 = all heads or panicles visible). The swards were harvested by a forage plot harvester (Haldrup). The cuts at pasture stage were carried out when the stands were approx- imately 30 cm high. There were three to five cuts. For grass species, the first silage crop was har- vested when 20% of heads or panicles had ap- peared. In Ruukki, mixtures containing clover were cut later, at the start of clover flowering. In Rovaniemi, all plant species and mixtures were 481 AGRICULTURAL SCIENCE IN FINLAND Table 2. Fertilization of trial plots during years of harvest in 1988-1992. Harvest Locality Nitrogen/yield Total system 1 2 3 4 N P K Pasture Rovaniemi 80 50 40 40 210 35 140 Ruukki 90 60 50 200 33 133 Silage Rovaniemi 110 80 190 32 127 Ruukki 120 80 50 250 42 167 Hay Rovaniemi 80 60 140 23 93 Ruukki 90 70 160 27 107 Mixed stands with red clover (all harvesting systems): Rovaniemi 62 62 60 108 Ruukki 40 40 60 108 usually harvested at the same time. Each year, two or three silage crops were harvested. Hay swards were harvested when the stands were in full head or panicle and red clover was in full flower. In Ruukki, the last cut was carried out right at the beginning of September, and in Ro- vaniemi around 20th August. Botanical composition was determined from combined samples of about 500-1000 g from all replicates of the treatments. In some cases, the botanical composition of the pure stands of tim- othy, meadow fescue, meadow grass and smooth brome grass was assessed visually as the cover- age of sown and unsown species. One represent- ative crop sample from different replicates of each treatment was taken and analysed for dry matter, crude protein and fibre. Dry matter was determined by drying two parallel 200 g sam- ples of the chopped plant, first for two hours at 100°C and then for 14 hours at 60"C. For total nitrogen, the plant samples were analysed with the Kjeldatherm system (Gerhardt, Germany) and for fibre content with the Fibertec system (Tecator, Sweden). The digestibility of the or- ganic matter was tested in vitro by the cellulase- enzyme method of Friedel (1990). The effects of the harvesting systems and species and their interactions were determined by analyses of variance. For dry matter and crude protein yields the analyses ofvariance were car- ried out by the SAS program. The significance of the differences was tested using Tukey’s test (LSD P < 5%). Due to the very different climatic conditions at the two research stations, experimental data were examined separately. Analyses of variance were made only for dry matter and protein yields. The crude protein yields of the replicates of the treatments were calculated by mean crude pro- tein content of dry matter. Because of the lack of replicates, statistically reliable analyses could not be made for the botanical composition and qualitative values of grass forage. At both trial sites the weather was warmer and rainier than the average during the trial pe- riod. In Ruukki, the growing period (daily mean temperature above +5°C) averaged 160 days, the effective temperature sum (degree-days, base +5°C) 1102°C, and the precipitation in May-Sep- tember 314 mm. In Rovaniemi, the growing pe- riod was 132 days, the effective temperature sum 922°C and the precipitation 295 mm. The aver- age number of days with snow cover in Ruukki was 147, and in Rovaniemi 181. In all winters, the soil froze before the permanent snow cover formed. 482 AGRICULTURAL SCIENCE IN FINLAND Nissinen, O. & Hakkola, H.: Effects ofcultivation technique on grassland production Vol. 4: 479-494. Results and discussion Sward overwintering The effect of harvesting method on the amount ofwinter damage was relatively slight (Tables 3 and 4). In Ruukki, most winter damage occurred in fourth- and fifth-year swards, and the main causes of damage were frost and ice scorch. In Rovaniemi, an increase in damage due to low- temperature fungi was seen from the second crop year. At both trial sites there was more damage, on average, in swards harvested at the silage stage than in pasture or hay swards. In Ruukki, timothy suffered the least winter damage and meadowfescue the most. In Rovaniemi meadow fescue overwintered as well as timothy. Smooth brome grass had the highest annual variation in winter damage. At both trial sites, there was less winter damage in mixed swards than in pure stands. According to this trial, timothy thrives con- siderably better than meadow fescue in Ruukki, which is situated on the coast, where the snow cover is shallow. Meadow fescue was most se- verely damaged by frost and ice scorch in old swards. Timothy has better resistance to ice en- casement and frost than meadow fescue (Gud- leifsson 1986). The winter climate in Rovanie- mi is stable and the snow cover continuous throughout the long winter. As a result, attacks by snow moulds are a frequent problem. Meadow fescue is more resistant to snow scald (Scle- rotinia borealis) than timothy (Nissinen and Sa- lonen 1972, Årsvoll 1977). This explains the good overwintering of meadow fescue in Rova- niemi. In this trial, the poorer overwintering of sil- age swards than of pasture swards may have been due to the timing of the last cut rather than to the harvesting system. For many years, the last cut was carried out earlier in silage swards than in pasture swards, and the aftermath left for overwintering had time to become more lush before the onset of winter. This increased the incidence of pink snow mould (Fusarium nivale) and of speckled snow mould (Typhula sp.) in the swards. Dry matter yields According to the statistical examination of dry matter yields, the differences between harvest- ing systems and plant species, and the interac- tion of these variables, were significant at both trial sites (Tables 5 and 6). Increasing the number of cuts reduced the total yield of plant species and mixtures of plant species. The combined yield of dry hay and af- termath was the highest, and the yield of swards cut at the pasture stage was the lowest. The only exceptions to this were meadow fescue in Ruuk- ki, and meadow grass and smooth brome grass in Rovaniemi, which gave the highest yields of dry matter harvested at the silage stage. The ef- fect of harvesting system on dry matter yields was greater in Rovaniemi than in Ruukki. At both trial sites, production dropped sharply in fourth- and fifth-year swards. In Ruukki, the plant with the highest aver- age yield was smooth brome grass and in Rova- niemi, meadow fescue. Timothy yields were con- siderably higher in Ruukki than in Rovanie- mi. Meadow fescue, in contrast, thrived more poorly than timothy in Ruukki, but in Rovanie- mi gave higher yields than timothy. The highest yieldingplant species mixture was timothy and mead- ow fescue and the lowest timothy and red clover. The total yields of pasture swards in Ruukki were 5500 to 7680 kg/ha in the first- to third- year swards, and 2180 to 4200 kg/ha in the fourth- to fifth-year swards. The yield variations between plant species in Rovaniemi were 3340 to 6310 kg/ha and 1570 to 4900 kg/ha, respect- ively (Table 6). The highest yielding plants were meadow fescue and meadow grass and the mix- ture of timothy and meadow fescue. The lowest total yield with four cuts was obtained from smooth brome grass. A comparison of swards of different ages shows that yields of dry matter dropped most rapidly in timothy and in smooth brome grass (Figs. 1 and 2). 483 AGRICULTURAL SCIENCE IN FINLAND Nissinen, O. & Hakkola, H.: Effects of cultivation technique on grassland production Table 3. Average winter damage and the proportion (%) of sown plant species in first harvest of first- to fifth-year swards in Ruukki in 1988-1992. Winter Percent sown plants Plant species and damage Year of ley harvesting system % 1 2 3 4 5 Timothy Pasture 3 100 100 100 40 61 Silage 7 100 100 100 100 49 Hay 2 100 100 100 47 31 Meadow fescue Pasture 20 100 100 100 100 39 Silage 22 100 100 100 47 21 Hay II 100 100 100 24 13 Meadow grass Pasture 19 73 100 100 100 60 Silage 21 77 100 100 100 50 Hay 9 100 100 100 73 53 Smooth brome grass Pasture 21 100 100 39 85 15 Silage 12 100 100 100 100 26 Hay 12 100 100 100 87 93 Timothy/red clover Pasture 5 Timothy 92 82 81 47 56 Red clover 5 18 7 3 12 Silage 6 Timothy 90 52 57 47 44 Red clover 7 45 30 22 28 Hay 5 Timothy 87 77 62 55 56 Red clover 13 20 23 2 10 Timothy/meadow fescue Pasture 15 Timothy 73 50 27 25 35 Meadow fescue 25 50 65 40 13 Silage 19 Timothy 79 35 46 28 41 Meadow fescue 18 53 50 31 16 Hay 6 Timothy 75 54 30 20 36 Meadow fescue 21 43 63 28 11 Timothy/red clover/meadow fescue Pasture 9 Timothy 63 37 22 25 25 Red clover 3 26 4 1 14 Meadow fescue 32 37 67 50 16 Silage 14 Timothy 56 41 53 28 35 Red clover 9 29 27 6 19 Meadow fescue 31 28 17 36 20 Hay 8 Timothy 48 48 36 46 51 Red clover 15 26 10 1 15 Meadow fescue 35 23 41 IS IX 484 Vol. 4: 479^94. Table 4. Average winter damage and proportion (%) of sown plant species in first harvest of first- to fifth- year swards in Rovaniemi in 1988-1992. Winter Percent sown plants Plant species and damage Year of ley harvesting system % 1 2 3 4 5 Timothy Pasture 7 99 100 90 62 78 Silage 19 95 100 78 64 49 Hay 18 94 100 97 80 71 Meadow fescue Pasture 14 98 100 99 97 92 Silage 16 92 100 90 96 73 Hay 14 92 100 99 99 89 Meadow grass Pasture 11 99 100 98 99 94 Silage 14 97 100 96 96 77 Hay 14 82 100 92 96 66 Smooth brome grass Pasture 22 99 100 85 50 44 Silage 30 99 100 89 79 60 Hay 16 73 95 77 69 18 Timothy/red clover Pasture 5 Timothy 98 30 77 68 58 Red clover 1 67 14 9 12 Silage 22 Timothy 97 16 66 56 55 Red clover 1 83 21 22 9 Hay 23 Timothy 98 14 49 45 55 Red clover 1 85 46 41 17 Timothy/meadow fescue Pasture 9 Timothy 89 24 4 4 3 Meadow fescue 10 74 95 92 91 Silage 16 Timothy 93 7 5 1 3 Meadow fescue 6 92 94 98 68 Hay 10 Timothy 93 44 10 4 11 Meadow fescue 6 55 89 88 72 Timothy/red clover/meadow fescue Pasture 7 Timothy 92 16 14 7 8 Red clover 1 52 11 16 3 Meadow fescue 6 31 74 76 79 Silage 15 Timothy 84 15 20 7 1 Red clover 2 75 18 15 5 Meadow fescue 13 9 61 74 71 Hay 8 Timothy 86 7 9 6 7 Red clover 3 84 29 28 5 Meadow fescue 9 8 61 63 85 485 Nissinen, O. & Hakkola, H.: Effects ofcultivation technique on grasslandproduction In Ruukki, the highest yielding silage plants were smooth brome grass and timothy and in Rovaniemi, meadow fescue and meadow grass. The lowest yields were obtained from mixed swards oftimothy and red clover. The total yield of young swards in Ruukki was 7240 to 9620 kg/ha, and in Rovaniemi 5030 to 7330 kg/ ha. In old, fourth- to fifth-year swards, the lowest yields in Ruukki were obtained from meadow fescue, 1980 kg/ha, and in Rovaniemi from timothy, 2800 kg/ha. In Ruukki, production of grass for silage was highest with smooth brome grass, 3800kg/ha, and in Rovaniemi, with meadow fes- cue, 5980 kg/ha (Table 6). The yields of hay swards, including after- math, were generally higher than those of silage swards (Tables 5 and 6). In Ruukki, the highest yielding plant in hay swards was smooth brome grass, which had an average dry matter yield of 10640 kg/ha in the first- to fifth-year swards. In Rovaniemi, meadow fescue had the highest av- erage yield, 7170 kg/ha. In hay swards, timothy also thrived well at both trial sites. Aftermath accounted for one-third of the total dry matter yield an average. It is clear from the trial that the economic use of sown grassland can not be prolonged with the plant species studied in any harvesting sys- tem. The yield ofpasture and silage swards can, however, be significantly increased with the cor- rect choice of plant species. In the trial, timothy and smooth brome grass were highly unsuitable for harvesting at the pasture stage, which ex- plains well the poor yield production ability of timothy-dominated pasture swards in northern Finland. Meadow fescue and meadow grass also thrived well when there were several harvest cuts during the growing season. The yield formation of meadow grass was more rapid in Rovaniemi than in Ruukki, which supports the view of An- dersson (1988) that meadow grass thrives relat- ively better the farther north it is grown. In the trials dry matter yields were increased in plants harvested at a later stage of develop- ment, as found also by Raininko (1968). The smaller differences between total yields of sil- Table 5. Average dry matter yields of different harvesting systems and plant species in Ruukki and Rovaniemi in 1988- 1992 A. Harvesting system B. Plant species Statistical significance P SH 1 2 3 4 5 6 7 A B Ax B SE Ruukki 1-3 year 6700' 8520» 9190» 8620ab 8530"’ 8240b 9000 ’ 7040 8210 7320' *** *** *** 165 4-5 year 3120b 3230b 3920“ 2850'd 2310d 3830b 5000“ 2940'“ 3560'b 3450'h * *** *** 165 1-5 year 5310 6400b 7080“ 6320b 610Ob 6510b 7400“ 5400“ 6350 b 5770“ *** *** *** 145 Rovaniemi 1-3 year 5050b 6500“ 6610 5230“ 7080“ 6490b 5310“ 5490“ 691Ob 5860' ** *** *** 130 4-5 year 3290 4500b 4940“ 2980 5840 4520 2970' 3420 5380b 4580' *** *** *** 145 1-5 year 4340b 5700“ 5940 4330 6580 5700b 4370 4660 6300 5350 ** *** *** 130 *P < 0.05 **P