Studies on the nutrition of rice plant . III. Partial efficiency of nitrogen absorbed by rice plant at different stages of growth in relation to yield of rice.
Tanaka, A.; Patnaik, S.; Abichandani, C.T.
Proceedings Indian Acad Science Sect B 49(4): 207-216
Rice plant of medium maturity, grown under low nitrogen supply (10 ppm) shows two peak periods of partial efficiency for nitrogen, when nitrogen taken up by the plant is most efficiently utilized in increasing grain yield. First such period occurs at the tillering stage and the second at flowering, between the boot and the milk stages. Nitrogen taken up by the plant between tillering and ear-initiation plays role in increasing tiller and panicle number per plant. During panicle development, from ear-initiation to flowering, nitrogen taken up increases number of filled grains per panicle and, after flowering, it increases effective 1,000 grain weight. The first period of maximum partial efficiency is, therefore, for increasing tiller number and the second for increase of panicle weight. If, however, the plant is grown at high levels of nitrogen (60 ppm) from the start, nitrogen taken up during the vegetative stage, up to ear-initiation is stored in the body of the plant and is used in the later growth and development, even if nitrogen supply is cut off later. High nitrogen supply, after ear-initiation, has a detrimental effect on growth and decreases grain yield because of decrease in number of filled grains per panicle and 1,000 grain weight. Chaffiness of panicle, under this condition, also markedly increases and the plant becomes more susceptible to neck infection due to blast.