In this study, we aimed to clarify how the spatial heterogeneity of a semi-natural grassland community at both the community and species levels is affected by grazing intensity. We examined three pastures with different grazing intensities light : (Pasture L), medium (Pasture M) and heavy grazing (Pasture H). Heterogeneities at both levels ranged from random/low to aggregated/high. The spatial heterogeneity at the community level was high in Pasture L, and low in Pastures M and H. The differences among the spatial heterogeneities at the community level were due to most of the dominant species in Pasture L having a higher heterogeneity than those in Pastures M and H. Pasture L was composed of a mixture of many species that had high heterogeneities, but Pastures M and H were composed of both highly heterogeneous species and weakly heterogeneous species. These differences in the spatial heterogeneity at the species level can be partly explained by the propagation types (clonal or non-clonal) of the species. The results of this study suggest that grazing intensity altered species composition and the spatial heterogeneity at the species level, and as a result, when grazing intensity was heavy, the spatial heterogeneity at the community level was low.

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Nitrogen (N) dynamics were studied through monitoring from June 1999 to June 2001 in grassland of Tsukui Region, Kanagawa Prefecture, Central Japan. Atmospheric N inputs were estimated by the determination of dissolved inorganic nitrogen (DIN : NO_3^- + NO_2 + NH_^4〜) and dissolved organic nitrogen (DON) in open bulk precipitation. Annual atmospheric DIN inputs were 12.5 kg N ha^<-1>yr^<-1> (1999/2000) and 13.0 kg N ha^<-1>yr^<-1> (2000/2001), respectively. Total dissolved nitrogen (TDN : DIN + DON) inputs originating from atmosphere were 19.9 kg N ha^<-1> (1999/2000) and 25.1 kg N ha^<-1>yr^<-1> (2000/2001) in open bulk precipitation of grassland. Annual atmospheric TDN inputs corresponded to 28% (1999/2000) and 35% (2000/2001) of the local standard nitrogen fertilizer application of 72kg N ha^<-1>yr^<-1>, respectively. Annual atmospheric DON inputs were 37% (1999/2000) and 48% (2000/2001) of TDN. In soil solution, TDN concentration increased, depended on the predominant NO_3^- with soil depth up to 40 cm. At 10cm depth of soil, DON concentration in soil solution showed high level as high as the atmospheric DON concentration. In this study, atmospheric DON was considered as an important source for N cycle in grassland ecosystem. The local standard level of N fertilizer application in grassland of Tsukui area caused the N excess as a result of no consideration of the atmospheric N input. This study recommends that it is necessary to reconsider both application amount of N fertilizer and atmospheric N input as total N (DIN+DON) input.

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This study was conducted to determine the changes of nutrient composition and losses of during field curing in hay and silage making, and to develop prediction equations estimating the changes and losses. Average concentrations of organic cell wall (OCW) and organic b (Ob) were increased, and organic cell content (OCC), organic a (Oa), estimated total digestible nutrient (TDN), crude protein (CP), phosphorus (P) and potassium (K) decreased during field curing. Average temperature had a significantly positive correlation coefficient with the decrease in TDN concentrations in field curing. Accumulative rainfall had a significantly positive correlation coefficient with the decrease in K concentrations. Dry matter harvested had significantly negative correlation coefficients with losses of TDN, CP, P and K. The following equations to estimate the decrease in TDN concentration and TDN loss during field curing were developed by multiple regression analyses : TDN decrease (%)=4.13 + 0.15 × ARF + 1. 37 × TED - 13.74 × 3^<rd>H TDN loss (%)= 48.85 - 44.12 × DMH + 2.09 × TED + 12.95 × 1^<st>H (ARF ; accumulative rainfall (mm), TED ; tedding (times), 3^<rd>H ; third harvest (dummy variable), DMH dry matter harvested (t/10a), 1^<st>H ; first harvest (dummy variable)) The more precise equations to estimate the loss in TDN, CP, P and K were derived by dividing the data into mono and mixed species pasture groups than pooling the data.

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To clarify the selection criteria of the resistance to sheath blight (Rhizoctonia solani Kuhn) in Sorghum, a field inoculation test was carried out in 1985. The materials used were 72 varieties and lines, which were classified into grain type, dual purpose type and sorgo type by objective of use. The most pathogenic isolate to sorghum, AG-1, that had been obtained from sorghum at the National Grassland Research Institute, was inoculated onto barley grains. The grains were spread on the hill and covered with soil two months after seeding. Resistance to the disease was evaluated by the relative lesion height (RLH), which is the ratio of the height of lesion on the sheath (HL) to flag leaf collar (HF) at maturity. Yield loss by the disease was evaluated by the relative dry matter weight (RDM), which is the ratio of the dry matter weight of inoculated plants to non-inoculated plants. The HL of 72 varieties in inoculated plants varied from 9 cm to 70 cm, and the RLH varied from 7.4% to 100%. The RDM varied from 24.8% to 100%. There were varietal differences in the yield loss by sheath blight among 72 varieties. The relationship between RLH and RDM was fitted by reciprocal model significantly (p<0.001). The reciprocal model for RDM, as based on the relationship between RLH (x) and RDM (y), was as follows : 1/y=0. 0100 + 0.0002 (x-14.2) The common criteria of the resistance, which are considered to be RLH of less than 200o and HL of less than 20 cm from the relationship between RLH and HL, is effective from the viewpoint of the relationship between RLH and RDM

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It has been reported that nuclear DNA content shows close correlations with geographical distribution in natural populations of orchardgrass (Dactylis glomerata L.) in central Europe (REEVES et al., 1998). D. glomerata has established dominant natural populations in disturbed habitats in the northern part of Japan, but the population abundance is less in the eastern part of Hokkaido, the northernmost island of Japan, because of winter injury. In this study, we examined the variation in nuclear DNA contents in natural populations of D. glomerata along the abundance gradient in the eastern part of Hokkaido. Relative abundances of natural populations were recorded at 16 sites, and their nuclear DNA contents were measured using a flow cytometer. A significant difference was found between nuclear DNA contents in the populations (p<0.001), and nuclear DNA content showed a positive correlation with relative abundance (r = 0.610) and with lowest temperature before snow cover (r = 0.504) at the sites. The results of this study suggest the association between variation in nuclear DNA content and ecological conditions at growing sites

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To evaluate the white clover (Trifoliam repens L.) populations that exist in mainly natural lawn-type grasslands of the northern-Tohoku region, image analysis was applied to quantify the eight leaflet features : perimeter (mm), roundness, asymmetry of a leaflet with respect to the midrib (%), total leaflet area (Total area, m^2), midrib length/maximum leaflet width (XY-ratio, %) ratio of the front area over the top of a midrib to the total leaflet area (Front area, %) ratio of the diamond area marked by the midrib and the maximum-width diagonal lines to the total leaflet area (%) and the location of the centroid of a leaflet along the midrib (%) The last five features were highly significant among thirteen populations (p<0.00l, p<0.00l, p<0.0l, p<0.00l, and p<0.0l, respectively). The cluster analysis was performed by using the four significant shape features other than Total area divided into three groups. One classified group, mainly collected in the artificial pastures, had leaflet shape profiles of a high XY-ratio and a small Front area. Another group, characterized by low XY-ratios, contained many of the native lawn-type grasslands. The cultivar, North White, had leaflet shape features that were unique and formed a group by itself.

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In this study, competition between white clover and weeds was ecologically observed for the establishment of a rational culture technique in white clover cultivation. The field test was conducted using white clover preceding plots and sweet corn preceding plots. In the white clover preceding plots, the white clover was extinct though the competition with the weed, and the weed finally flourished. In the sweet corn preceding plots, the white clover won the competition with the weed, and flourished, and the weed almost disappeared. Based on these above results, the difference of white clover growth in both test sections was clarified by a statistical technique and the isocline method. The competition relation in both test sections was modeled using Sakai-Ichimura model modified from Lotka-Volterra model. The competitiveness of the white clover with the weed in the white clover preceding plots and density effect of white clover affected on the competition coefficients a and β as system parameters of the model.

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This study was conducted to investigate the effects of growth temperatures and cutting heights on the regrowth of a tropical forage legume, phasey bean (Macroptilium lathyroides (L.) Urb.). Phasey bean was grown outdoors in pots and treated with three different growth temperatures (20℃, 25℃ and 30℃) from the 28th day after sowing. On the 47th day after sowing, the plants were cut at height of 7.5cm or 15cm above the soil surface. The plants were collected on the 2nd, 6th, 13th and 28th day of regrowth, and measurements were conducted for dry matter yield, nitrogen and total non-structural carbohydrate (TNC) contents and nitrogen fixation activity. After the cutting treatment, the dry matter weight of the plant tops in all temperature treatments decreased until the 2nd day, and that in the plant root showed a decrease until the 13th day of regrowth. The dry matter weight of whole plant cut at a height of 15cm was significantly higher (P<0.01) than that cut at 7.5cm on the 28th day of regrowth. In the 15cm cutting treatment, the dry matter weight was significantly higher (P<0.05) at 25℃ and 30℃ than at 20℃, while there was no significant response of dry matter weight to temperatures in the 7.5 cm cutting. The leaf area ratio (LAR) in the 15cm cutting treatment was higher than that in the 7.5cm cutting treatment. TNC content, nodule weight and nitrogen fixation activity in all treatments decreased until the 6th or 13th day after cutting. There were remarkable decreases in TNC content at three temperatures in the 7.5 cm cutting treatment and at 30℃ in the 15cm cutting treatment. In conclusion, phasey bean showed higher regrowth at 25-30℃ and 15cm cutting height than at 20℃ and 7.5cm cutting height. This was mainly due to differences in the amount of storage nutrients available for regrowth.

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Four Japanese Black heifers were used for two experiments. In experiment 1, two groups (spraying group of the repellent and non-spraying group) were set up. The experimental heifers grazed at the same time from 9:00 to 15:30 in the pasture. The number of pest flies, and grooming behaviour against the pest flies and grazing behaviour of focal animals were recorded continuously for two hours from 10:00. In the spraying group, time budget and mean duration of grazing, and the time spent and bites at feeding station (following as FS) were larger than in non-spraying group significantly. On the other hands, the number of steps between FSs in spraying group was fewer than non-spraying group significantly. In experiment 2, two groups as experiment 1 were set up, the heifers fed enough oats hay and formula feed at 8:30 and 15:30 were grazed from 9:00 to 12:00 in the pasture of little herbage mass. The resting behaviour of focal animal was recorded at one-minute interval, and grooming behaviour was observed continuously for two hours from 10:00. Time budget and mean duration of recumbency behaviour in spraying group were more than non-spraying group. In both two experiments, the number of pest flies and grooming behaviour in spraying group were fewer than non-spraying group significantly. These results indicate that pest flies induce grooming behaviour frequently, and their attack did not secure stable grazing and recumbency behaviours of grazing cattle in summer.

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We examined a method for sampling round bales and an effect of inoculation of lactobacilli (Lactobacillas rhamnosus or Lactobacillus plantarum) for whole-plant rice silage. In an experiment of laboratory-scale silage, inoculation of L. plantarum was most effective in improvement of the fermentation quality. In another experiment of the round bales, chemical components in the silage samples were largely variable among different sampling sites in each bale. However, the chemical components in mixtures of these samples were less variable within each bale than those in the individual samples. In this experiment, inoculation of the L. rhamnosus was proved to be effective by comparing the mixtures of the inoculated samples to those of the control samples. These results suggested that the sample mixtures could represent the round bales.

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This study was carried out in order to clear the critical daylength and its sensitive time of Kazetachi with a critical daylength less than 12.5 h. Days to flower initiaion were almost the smallest and not different among varieties at 12h daylength. The results suggest that an optimal daylength of sorghum is 12 h. A threshold daylength for initiating flower of Kazetachi was 12.25 h, so a critical daylength is considered to be around 12.25 h daylength. And its sensitive time at 12.25 h daylength was observed from 10 to 30 days after emergence of seedling (3 to 5 leaf stage).

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