Effect of stocking rate and grazing initiation date on milk production was studied. About two hectares grass-clover mixed sward was divided evenly into two paddocks and each paddock was grazed by five (G5) and seven (G7) Holstein lactating cows. Grazing was commenced on May 1 in 1995 (early initiation date) and May 20 in 1996 (late initiation date). Herbage mass was higher in G5 than in G7. CP content of herbage was slightly higher and NDF content of herbage was lower in G7 than each in G5. Late initiation date brought higher herbage mass during grazing period than that of early initiation date. CP content of herbage was lower in late initiation date than that in early initiation date and NDF content of herbage was higher in late initiation date than that in early initiation date, in particular from July to August. Total herbage intakes of G5 and G7 during grazing period in early initiation date were 7.2 and 8.2tDM/ha and those of G5 and G7 in late initiation date were 7.2 and 7.8tDM/ha, respectively. FCM yields derived from herbage in G5 and G7 during grazing period in early initiation date were 8.2 and 9.8 t/ha and those of G5 and G7 in late initiation date were 7.8 and 9.3 t/ha, respectively. These results suggested that high stocking rate produced more milk output per unit area, but date of grazing initiation had no clear effect on milk production.

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An experiment was designed to examine the effect of pre-grazing grass height on milk production by dairy cows under rotational grazing. Two levels of pre-grazing grass height were prepared, and one was maintained at low grass height (20 cm GH20) and the other was maintained at high grass height (30 cm GH30) throughout the grazing season by adjusting rest period. Cows were grazed for five hours per day at the stocking rate of 7.5 cows/ha from May to October. GH20 brought higher crude protein and lower neutral detergent fiber contents of herbage than those of GH30. GH30 brought higher herbage allowance and, hence, higher herbage intake per animal than that of GH20. Supplementary feed intake and total intake were higher in GH20 than in GH30. Milk yield per cow was slightly higher in GH20 than in GH30, but there was no significant difference between the treatments. Milk yield from herbage per cow was also not affected by grass height. The efficiency of herbage utilization on FCM yield (FCM kg/TDN kg) was tended to be higher in GH20 than in GH30. Herbage intake per unit area was higher in GH30 than in GH20 and the difference reached approximately 1 tDM/ha. However, the difference of milk yield per unit area, derived from herbage, was small (GH20:11.1 t/ha vs. GH30:11.5 t/ha). Low grass height increased herbage nutritive value and would increase nutrient intake or utilization, whereas high grass height increased herbage intake because of high herbage allowance that was brought by high herbage mass. These results would offset the effect of pregrazing grass height on milk output per unit area.

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In the present study we examined the relation between the survival rate of mulberry trees planted into pastures and cattle grazing. Planting methods of mulberry trees were in rows (with a spacing of 3 m between rows and 0.7 m between plants 4,762 trees/ha) and in sparsely planting (with pairs of mulberry plants planted per spot 2,222 trees/ha). The survival rate of mulberry trees subject to grazing decreased yearly, and was 16-28% in row planting and 39-56% in spersely planting after four years of grazing. On the contrary, most mulberry trees harvested by clipping still survived after four years. Browsing and trampling by cattle thus inflicted relatively severe damage to the mulberry trees. Unless a useful method to control cattle grazing of mulberry is found, the use of mulberry fields as grazing pastures cannot be practically implemented.

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In the semi-natural grasslands of Aso region,the vegetation has historically been maintained through artificial treatments such as controlled burn. In several grasslands location,however, these burns have been discontinued recently due to labor shortages. Therefore,we compared the vegetation where controlled burns have been stopped and that of grasslands where burns are still performed. For our study,we selected five Miscanthus-grasslands sites:one site where controlled burns continue,and four discontinued-burn sites that vary depending on when controlled burns were stopped (one year ago,six years ago, eight years ago,and approximately thirty years ago). In all five investigatory sites,the community coverages were almost 100%, with community heights between 110-178cm. We observed a higher number of plant species in the site where controlled burns were still practiced compared to the sites where the practice has been discontinued. Where controlled burns had been stopped,the standing dead litter were calculated to be 3 to 8 times that found in the controlled-burn site. The litter were seen to be between 162-602g/m^2 in the stopped-burn areas,while such matter was rare where controlled burns were still performed. In the discontinued-burn grasslands,we found lower coverage,weight and number of stems of Miscanthus sinensis than that found in continued-burn area. The degree of succession (DS) in the discontinued-burn grasslands area tended to be higher than that in the continued-burn area. Species diversity,H',was lowest in the area where burning was stopped one years ago,with H'tending to be higher as the period of burn discontinuance increased. In the mentioned above,it was cleared that stopped-burn made standing dead litter increased temporarily,and it was suggested that vegatation of the semi-natural grassland where controlled burns have been stopped changed to forest gradually.

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The objective of this study was to determine the effects of plant height in a meadow fescue (Mf) pasture being grazed on plant yield,nutritive value and persistency of the pasture. The effect of integration of conservation with grazing on persistency of the Mf pasture was also investigated. When pastures were grazed when plant height had reached 20cm,yield and nutritive value of the plants in the Mf pasture were the same as those of plants in the perennial ryegrass (Pr) pasture, the efficiency of utilization of the Mf pasture was greater than that of the Pr pasture,and persistency of the Mf pasture was inferior to that of the Pr pasture. When the Mf pasture was grazed when plant height had reached 25-30cm,the plant nutritive value was slightly lower but the plant yield was 33% greater and persistency of the pasture was improved compared with those in the case of grazing at a plant height of 20cm. There was little improvement in persistency of the Mf pasture by integration of conservation with grazing.

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Two experiments were carried out in 1999 and 2000 to determine chemical composition,characteristics of silage fermentation and nutritive value of Galega (Galega orientalis Lam.). In 1999,the full-bloom galega and alfalfa harvested on the same day,and three types of silage,direct-cut silage with 0.5% formic acid (DF silage),wilted silage with no additives after 1 day of wilting (W-1 silage) and wilted silage with no additive after 3 days wilting (W-3),were prepared to investigate the effects of wilting on chemical composition and characterstics of silage fermentation. Contents of CP and undegraded CP of full-bloom galega were higher than those of alfalfa harvested at the same time. The quality of DF silage and W-1 silage of both alfalfa and galega was poor:both types of silage had high pH and high concentrations of ammonia -N and butyric acid. The quality of W-3 silage of both alfalfa and galega was good,although pH was high. In 2000,the nutritive value of wilted silage of the first growth galega harvested at full bloom was investigated using four sheep in cross-over design. Dry matter digestibility (DMD) and total digestible nutrients (TDN) of galegan silage were 56.9% and 53.6%, respectively, similar to those of alfalfa silage (DMD;57.1%,TDN;52.0%). The results indicated that,like alfalfa,suppression of clostridia activity and improvement in fermentation quality of silage are possible for galega if galega is wilted to a DM levels of more than 50%. The results also indicated that galega has a considerable potential as a new fodder legume for ruminants in Japan.

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Changes in growth and nitrate-nitrogen concentration of oat (Avena sativa L.) and sorghum (Sorghum bicolor Moench) from November to January were investigated under heavy nitrogen applied conditions in 1998 and 2001. Nitrate-nitrogen concentrations based on dry matter of sorghum plants did not decrease during the experimental term. On the other hand, nitrate-nitrogen concentration based on dry matter of oat plants dramatically decreased with increasing dry matter content, while no obvious change was observed for nitrate-nitrogen concentrations based on fresh matter. The decrease in nitrate-nitrogen linked with the increase in dry matter content for oat. Forage quality of oat plants did not decrease even if the plants were harvested at mid winter with a dry matter content of over 60%. In conclusion,dry matter content of oat plants should be increased to reduce nitrate-nitrogen concentration under excessively nitrogen fertilized conditions. For this purpose,a heading day should be controlled to be before November. Sowing day for the oat cultivation to enhance dry matter content is calculated based on an average temperature of climatological grid map from south Tohoku to Kyushu district.

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This study was conducted to investigate the detailed distribution of the range of about 20×20km area by using the GPS unit and occurrence pattern of 13 invasive weed species such as Abutilon theophrasti,Cyperus esculentus,Sicyos angulatus and Solanum carolinense that are noxious weeds of forage crop fields. It showed that the most invasive weeds were abundant in paddy fields,forage crop fields and roadside in 1578 survey points,and that Bidens frondosa,A. theophrasti and C. esculentus were frequently appeared. The occurrence of A. theophrasti and C. esculentus was almost limited in the forage crop fields, although the over 50 percent of S. angulatus,Xanthium occidentale and Ambrosia artemisiifolia occurred in non-cultivated fields and furthermore invaded to the native vegetation fields. The point distribution map of the invasive weeds were made from the GPS data,intensive distribution was found in B. frondosa, A. theophrasti and C. esculentus,whereas Ambrosia artemisiifolia and S. carolinense showed the widely dispersed distribution. When made a circle from each distribution point to use a GIS tools and checked the connection pattern of the clamp,the radius of a circle of clamp and the connected clamp number were able to approximate with the index style decrease curve and there was the high correlations of or more r=0.95 with all species. Clamp data showed that the single occurrence was frequent in S. carolinense,A. artemisiifolia and Solanum spp. It is possible to use the GPS data for database of the future distribution expansion of the invasive weed with a geographic scale map,and that is effective for the Bio-resources and ecosystem protection to the invasive plants.

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