Abstract
Under various nitrogen conditions rice plants, var. Norin-No. 29 were cultivated and its influences on the ripening process were investigated. Results obtained mav be summarized as follows : (1) Grain yield increased with the increase of nitrogen, supplied during ripening period, but too much nitrogen reduced the yield. (2) Such effect of nitrogen were observed when the fertilizer was applied one week before heading time and 5 days after heading but could hardly be observed when it was given 18 days after heading. (3) The plants which were deficient in nitrogen were inhibited rather in the later process of ripening than, the earlier, but reverse result was observed in the plant which had the abandant supply of nitrogen. (4) The inhibition of ripening under nitrogen deficient contition was due to the decrease in photosynthetic activity of leaves but under excessive nitrogenic condition the inhibition of ripening was due to the inhibition of translocation of photosynthesized matter to panicle. (5) The lowest nitrogen level in average of about 1.0-1.4% from 5 to 35days after heading should be maintaind in the leaf blade in order to obtain the best ripening.
