水稲晩植による減収機構の解析 : (第5報) 苗代日数を異にした苗の生産能力

抄録

1. From our previous studies, it is evident that if the seeds sown sparsely in seed-bed they can produce higher yield, even when transplanted later than usual. But this method needs wide acreage and much labour to manage the seed-bed and there are some troubles in applying this. Then we tried to sow seeds lately in seed-bed and transplant seedlings lately to paddy fields because this method needs less acreage and labour. 2. Two varieties were used: "Sekiyama-No.2" is a heavy-panicle type and Ou-No.195" a mediate type. Seeds were sown at six different times to seedbed with ten days interval from 16th of April to 5th of June, and the seedlings were transplanted 20 or 30 days later than usual. 3. Seedlings Were transplanted individually with the rate of six hills per 3.3m (90.9 × 60.cm) in a paddy field in order to give a good enough space for growing. 4. Both varieties showed low yields when it was transplanted lately owing to decreasc of pancle numbers. 5. Wnen the both varieties were transplanted 30 days later than usual, and also "Sekiyama-No. 2" transplanted 20 days later than usual, the length of nursery period gave no influeuee on the yield. In other words there is no difference of yields between the rice crop derived from the seedlings grown for only 30 days and that derived from seedlings grown for as long as 70 days in seed-bed, when they were transplanted 30 days later than usual season.