Abstract
1) Newly bred N (Nasu)-line No. 4 of Italian ryegrass was sown to upland field from late August through late September of the next year at about half a month interval. 2) Germination was good at average daily temperature 6-23℃, while time to germination period being shorter at 12-26℃. Germination period at 5-20℃ was the day when integrated average daily temperature after germination reached 110-130℃. Germination below 5℃ was much retarded and that above 24℃ was inferior. 3) Inter-nodal growth of the grass was faster in calendaar days in accordance with earliness of germination period. But the days spent for about 1cm growth after germination was longer as earlier the sowing. 4) Total forage yield up to July was higher as earlier the sowing but the sowing from early August to late October gave 1.5-1.8 ton/a. Daily forage yield was higher when the grass was sown at August-October or February-March. 5) The followings were observed that above 5℃ in average daily temperature grass growth incresed, at 10-20℃ vigorous growth attained, at 20-25℃ growth declined as higher the temperature and above 25℃ serious summer depress of growth resulted. From above, it was made clear that production efficiency was highest with vigorous growth in April-June and next to this the efficiency was higher in October-November with good growth. 6) In crude protein content, differencies were not observed regarding to growth stage nor sowing period. 7) Better method of cultivating Italian ryegrass is to get higher forage yield with better production efficiency by effectively utilizing two seasons of optimum growth temperature in spring and autumn. In autumn when average daily temperature goes down below 25℃, it is desirable to sow seed as early as possible.
