Two different size of leaflet of white clover varieties, Grasslands Kopu (large-leaved) and Grasslands Tahora (small-leaved) were sown at the weight ratio of 1:1 with perennial ryegrass in 1994. Treatments with intensive and extensive grazing using Jersey heifers were carried out over four years, 1995-1998. The number of heifers per a unit of acreage in the extensive grazing treatment was a half of that in the intensive grazing treatment. Observed herbage mass from the extensive grazing treatment was higher than that from the intensive grazing due to different intensity of grazing. The proportion of white clover in the sward was significantly lower in the extensive grazing treatment compared with the intensive treatment. The proportion of white clover in a sward for the intensive grazing treatment was a proper content of 20-30% during the experiment period. One hundred samples collected from each sward after the experiment of grazing for four years were measured for the length of central leaflets. The stolon tips of sample plants were cut and transferred to new pots two times with the plants of original varieties, Grasslands Kopu and Grasslands Tahora for the purpose of removing the effect of plasticity through a different grown environment. A wide variation was observed in samples from the extensive treatment with the higher proportion of plants having long leaflets. In contrast, for the intensive grazing treatment, a variation was found with the similar to that of Grasslands Tahora, small-leaved variety. This strongly suggested that Grasslands Tahora dominated gradually during the experiment period. The small-leaved variety of white clover would be adapted to the intensive grazing system and become dominant in such swards. Grasslands Tahora was bred for hill country of New Zealand and had greater stolon density giving improved persistence under intensive grazing in addition to good winter survival. From this experiment it was suggested that small-leaved variety, Grasslands Tahora would be recommended for intensive grazed swards in the cool regions of Japan when grown with perennial ryegrass.

View full abstract

In this study, a number and distribution of dung pats in a grazing paddock and a seasonal change of the area of individual dung pats and dung patches were investigated through the grazing season. Five (LS) or seven (HS) Holstein lactating dairy cows were grazed on about one hectare grass-clover mixed pasture from May to October for two years. Cows grazed 5 hr/day (2.5hr×2) on each paddock under strip grazing management. In each grazing, number and position of dung pats on the paddock were recorded, and also seasonal changes of the area of a dung pat and dung patch were measured through two years. Mean density of dung pats on the pasture was 0.021 and 0.025/m^2 on LS and HS in individual grazing cycles. A distribution pattern of dung pats fitted Poisson distribution (random) on LS. The distribution pattern of dung pats on HS was negative binomial distribution (contiguous), then it became to be a random distribution with progress of grazing. The area of a dung pat gradually decreased through the season, although the dung itself did not disappear at the end of grazing season. Seasonal change of the area of a dung patch was affected by the month of dung dropped and grazing conditions, while the area of a dung patch changed quadraticically in most case. Total area of dung pat was linearly increased on both treatment. Total area of dung pats occupied 1.3-1.5% on the pasture at the end stage of grazing season. Total area of dung patches on the pasture was markedly increased after July and reached maximum level at September on both treatments. The maximum area of dung patches on LS and HS reached about 20 and 11% on the pasture.

View full abstract

Seasonal change in nitrogen uptake by pasture plants in tall fescue (Festuca aruadiaacea Schreb.) grazed pasture during two years from 1996 to 1998 was estimated from nitrogen content of pasture plants and from the data in our previous report about net production. We compared the change in uptake to the soil nitrogen contents and discuss the interaction between pasture plants and soil nitrogen. For convenience, we divided a year into 6 periods and calculated the nitrogen uptake by pasture plants in each period. It increased during the periods May to July and August to October, which were the periods just after the fertilizer applications. At the end of each of these periods, the plant nitrogen mass increased. At the same time, available nitrogen and inorganic nitrogen in the soil increased. The 2-year average of the annual nitrogen uptake by pasture plants was 45.1gN/m^2/year, and this value was 3.1 times higher than the amount of nitrogen applied as fertilizer. It was thought that the majority of plants nitrogen uptake seems to originate from soil nitrogen. Applications of inorganic nitrogen fertilizer directly increased the soil inorganic nitrogen and increased nitro- gen uptake by pasture plants. This suggested that the increase in inorganic nitrogen in the soil reduced the competition between plant and soil microbial biomass, and consequently activated microbial biomass in the soil (priming effect). Under the C/N ratio in the present study (9.5-12.6), it is thought that the activation of soil microbial biomass leads to mineralization of soil nitrogen. To know the interaction between pasture plants and soil nutrients seems to be a key to understanding nutrient flow in grazed pastures.

View full abstract

A trial treated by two levels of grazing frequency and N fertilization was conducted to compare and evaluate the effects of snow cover on sward vegetation and soil N on grazinglands. Significant differences in pre-snow grass mass between two treatment levels still maintained after snow melting. Positive responses of total mass and standing crop to different N fertilization levels found at pre-snow cover were not detected at post-snow cover. Grass to litter ratios reduced from pre- to post-snow cover, especially at low grazing frequency. Tiller density of grasses in same treatments did not differ significantly between pre- and post-snow cover, while N fertilization had positive effects on tillering either before snow cover or after snow melting. High N and frequent grazing caused increases in total nitrogen (TN) contents as 16.6 and 8.2% respectively during pre-snow cover. TN contents post-snow cover increased compared to pre-snow cover. There were significant increases in available nitrogen (AN) contents pre- and post-snow cover at high N fertilization, but no significant differences between grazing frequencies. AN contents after snow melting considerably rose as average 3.2-fold for that pre-snow cover.

View full abstract

Zoysia japonica Steud. is a dominant species in native pastures in Japan that is persistent even without fertilizer application. The purpose of this study was to determine the growth and increase of grazed Z. japonica plants under a deciduous forest at three tree densities (thin:30 trees/10 a, medium:44 trees/10 a and dense:63 trees/10a). Z.japonica sods were transplanted in March 1996. The rooting ratios of Z.japonica sods were 75, 86 and 98% under thin, medium and dense tree densities, respectively. The highest rooting ratio recorded under the dense plot was attributable to the higher soil water content that was maintained under the dense canopy. Frequency of occurrence and ground coverage of Z.japonica increased in all the plots in second and third year after transplanting. The most rapid increase in growth and highest dry weight of Z.japonica was recorded in the thin plot with 75% frequency, 60% coverage and 573g/m^2 dry weight in October of the third year. Estimated leaf area index (ELAI) of the trees increased gradually from the first year to the third year in all plots. The highest ELAI value was recorded in the dense plot throughout the experiment. Amount of tree litter decreased from year to year in all plots, and a little difference was recognized among treatments. Therefore, the rooting of transplanted Z.japonica under the tree canopies did not seem to be inhibited by shading within the range of thinning intensity examined, although the growth of Z.japonica (both in frequency and coverage) was higher under low density of 30 trees/10 a with 9 meter high.

View full abstract

In this field experiment, in vitro dry matter digestibility (IVDMD) and nitrogen content of tropical forage legume Aeschynomene americana L. grown in drained paddy field and upland field in 1994 and 1995 were examined. Three Aeschynomene americana strains (cv. Glenn, CPI 93556 and cv. Lee) and phasey bean (Macroptilium lathyroides (L.) Urb. cv. Murray) were sown in the drained paddy field and the upland field on June 1 every year. IVDMD and nitrogen content were measured at intervals of 15-20 days from July to November. IVDMD and nitrogen concentration in Aeschynomene and phasey bean reduced with plant growth, especially, from August to September of high air temperature period. In 1994, water stress was occurred in upland field grown plants, but large decreases in IVDMD and nitrogen concentration did not arise. Compared with upland field grown plants, drained paddy field grown plants had lower IVDMD, owing to rapid growth and higher dry matter yields. Significant partial correlation coefficients were recognized between IVDMD and dry matter yield or stem/leaf ratio, and between nitrogen concentration and dry matter yield or stem/leaf ratio in Aeschynomene. The main contribution factor to the rate of decrease in stem IVDMD of plant grown in the drained paddy field was days of vegetation in all Aeschynomene strains, and that in leaf IVDMD was air temperature in Glenn, days of vegetation in 93556 and solar radiation in Lee, respectively.

View full abstract

Animal performances of steers (Aberdeen Angus and Holstein) and heifers (Aberdeen Angus) were investigated under the two types of intensive grazing system (SS and NS) on timothy (Hokushu, TY) swards (total area of 2.4 ha). One of the four herds (2 treatments of SS and NS×2 replications) consisted of four steers and two heifers of Angus and two steers of Holstein. The four experimental swards were divided into 35 paddocks respectively. In SS, from May- mid-June, 43% of total paddocks were used for grazing. The other paddocks were harvested for ensiling at early June, and then all the paddocks were used for grazing until the end of experiment. Herds of SS were supplied grass silage made from respective swards from mid-July to end of grazing. On the other hand NS swards were not harvest at all and were grazed rotationally using all paddocks from May to October. Grazing animals of NS were not supplied silage. Result obtained were as follows: (1)The herbage allowance in the SS sward, were kept the sufficient level at 4 kgDM/100kgBW throughout the grazing season. On the other hand that of the NS sward were fluctuated 2-8 kgDM/100kgBW. (2)Though dry matter digestibility (DMD) of TY on the SS sward were kept on level of about 70% during summer season, in the NS sward DMD of TY were fallen under 65%. (3)Total weight harvested as roll ball silage from the SS sward were 3,865 kgDM and dry matter digest- ibility were 71%. Daily intake of silage in SS herds were estimated 3.6kgDM/head/day from late June to end of grazing. (4)In summer daily gain of SS herds (0.70 kg/day) was high as compare with NS herds (0.28 kg/day). Therefor the total daily gain of SS herds was also higher than NS herds (0.81kg/day and 0.65 kg/day respectively). Cumulative body weight gains per unit land area over grazing season was higher in SS herds (721 kg/ha) than that in NS herds (624 kg/ha).

View full abstract

We isolated three strains of lactic acid bacteria (LAB) from sorghum (Sorghum bicolor Moench) silage stored at 4℃ for two months. Fermentative properties of these strains were compared with those of Lactobacillus plantarum NGRI 0320 which was previously isolated and selected as a silage inoculant. 1. The LAB isolates were identified as L. curvatus from their physiological properties and the partial sequence of their 16S ribosomal DNA which were examined in this study. 2. Lactic acid productivity of the LAB strains were examined in a model system for ensilage using milled alfalfa (Medicago sati a L.) hay cube added with water. In this experiment, the L. curvatus strains produced lactic acid more rapidly at 4℃ and 10℃ than the L. plantarum strain. 3. Effect of inoculation with the L. curvatus strains on ensiling was examined by preparing laboratory-scale silage of Italian ryegrass (Lolium multiflorum Lam.). After 30 day storage at 4℃, inoculation with the L. curvatus strains effectively improved fermentation quality of the silage, whereas inoculation with the L. plantarum strain had little effect. This effect of the L. curvatus strains should be due to their lactic acid productivity. These results suggested that the L. curvatus strains are hopeful as silage inoculants at low temperature.

View full abstract

We examined fermentative properties of Pediococcus Sp. M-9, which was isolated from silage and was putatively identified as P. acidilactici, by using a model system for ensilage and laboratory-scale ensiling of guinea grass (Panicum maximum Jacq.) and obtained results as follows. 1. Physiological properties of this strain resembled those of P. acidilactici. 2. Pediococcus sp. M-9 grew faster in MRS broth added with more than 1 M of NaC1, KC1 or glucose than some other Lactobacillus Spp. strains and should have higher tolerance to low water activity. 3. Lactic acid productivity of Pediococcus sp. M-9 and the Lactobacillus spp. strains in a model system for ensilage was examined. In case of the dry matter content of 16.8%, the Lactobacillus spp. strains produced higher amount of lactic acid than that of Pediococcus sp. M-9, whereas Pediococcus sp. M-9 produced higher amount of lactic acid in case of the dry matter content of 63.5% perhaps due to higher tolerance to low water activity than that of the other strains. Pediococcus sp. M-9 produced lactic acid at 52℃ unlike the other strains. 4. In ensiling process of guinea grass (P. maximum) with 65.0% of dry matter content, the silage inoculated with Pediococcus ap. M-9 contained higher amounts of lactic acid than that inoculated with L. plantarum. These results suggested that Pediococcus sp. M-9 is hopeful as a silage inoculant for plant materials of high dry matter.

View full abstract

Three basidiomycetes, Pleurotus salmoneostramineus, Pleurotus cystidiosus, Auricularia polytricha, were in- oculated at 25℃ on a bagasse-basal media for 30, 60, 90, and 120 days without fruiting and investigated on effects on chemical structure and rumen degradability of bagasse. The basidiomycetes degraded more hemicelluloses and lignin in the media than celluloses;the most powerful species, Auricularia polytricha, degraded hemicellulose and lignin up to 31% and 40.4% , respectively. Those were also accompanied with extensive breakdown of cross- linkages between lignin and carbohydrates, as estimated by lower concentration of ferulate ethers after the inoculation. In contrast with lower degradation of celluloses by basidiomycetes, rumen degradability of celluloses in the basidiomycetes-inoculated bagasse was improved by about 250-400% of that of the original bagasse, in good agreement with microscopic observation of exposed cellulose microfibril around the hyphae. Lesser increased degradability of hemicelluloses in the rumen appeared to be associated with selective degradation of arabinose and xylose residues but not of uronic acids and glucose and mannose residues by the basidiomycetes. Changes in particle sizes, moisture retention, and cellulose crystalline index were also discussed in relation to the baggase degradability.

View full abstract

In order to clarify the relationship between forage production and the quality of napiergrass (Pennisetum purpureum Schumach cv. Wruk wona) in detail, changes in the respiratory activity (R_0, mg CO_2 dry matter weight^<-1> hr^<-1> at 25℃) and dry matter disappearance (DMD), which were in conflict with each other during aging, were investigated on each leaf and stem-nodal position of the tiller with four or more elongated internodes. In some plants, all of the fully expanded leaf blades were cut off to block the transport of assimilate from the same phytomer at three months after planting. The correlation between the nodal position and R_0 in the leaf was weak, while the R_0 and DMD in the internode of the stem decreased with the decline in the nodal position, suggesting that accumulation of senescent parts was predominantly processed in the stem. Defoliation of leaf blades caused no significant change in R_0 of the whole stem, suggesting that growth respiration was small in the stem. The mean respiratory activity (mR_0) and DMD in the whole tiller decreased markedly with aging and were mainly dependent on changes in the stem rather than the leaf. In the internodal stem, the DMD decreased constantly with the increase in the nodal position, whereas R_0 was severely decreased at the uppermost four or five inter- nodes, and then, was parallel to DMD at the lower internodes. This suggests that R_0 is closely correlated with the extent of DMD. The relationship between carbohydrate metabolism, R_0 and DMD in aging were discussed in accordance with the negligible effect of defoliation on the R_0. From these results, it is inferred in napiergrass with four or more elongated internodes, that aging and DMD should be predictable from the R_0.

View full abstract

Downward movement and leaching of nitrate-N was studied following cattle urine application (60gN/m^2) to bahiagrass (Paspalum noraturn Flugge) dominated pasture on 8 August (Aug. Plot) and 15 October (Oct. Plot) 1991. Soil samples were taken at 1-2 week intervals by auger (2 cm diameter, six cores per sampling) at 15 cm increments to a depth of 150cm. Ammonium- and nitrate-N analysis were carried out on 10% KC1 soil extracts. Water potentials were recorded by mercury manometer tensiometers installed at 10cm intervals to 150cm. Daily rainfall was recorded throughout the experiment (1 Aug. 1991-31 July 1992). Most of the urine-N was transformed to nitrate-N within two and five weeks after application in the Aug. and Oct. plots respectively. Downward movement of nitrate through the soil was influenced greatly by soil water conditions. Seasonal changes in the top boundary phase of downward water movement in the soil were estimated by the hydraulic gradients of water potential and located at about 60 cm throughout most of the season. Nitrate-N loss by leaching was estimated by measuring the amount of nitrate contained in the soil from top boundary to a depth of 150 cm. By this method, nitrate-N leached amounted to 21.5 gN/m^2 (35.8% of applied urine-N)and 34.9 gN/m^2 (58.2% of applied urine-N) in the Aug. and Oct. plots respectively.

View full abstract