Analysis of yield-determining process and its application to yield-prediction and culture improvement of lowland rice : LXXXVI. Relation between the nitrogenous nutrition and the constituting factors of the number of spikelets per unit area

Abstract

The relation between nitrogenous nutrition and the components of the number of spikelets per unit area was investigated and obtained the following results. 1. The number of panicles and primary rachis branches per unit area was mainly affected by the amount of nitrogen absorbed by the time of neck node differentiation, and little affected by the amount of nitrogen absorbed after the time of neck node differentiation. 2. The number of secondary rachis branches was mainly affected by the amount of nitrogen absorbed by the time of late spikelet differentiation, except the cases where an abnormally large number of spikelets were degenerated by the abnormal climate or an extremely large amount of nitrogen was absorbed in the reduction division stage. And at heading time, in general, the number of secondary rachis branches was correlated with the amount of nitrogen absorbed by heading time. 3. The relation between the number of spikelets per panicle and the amount of nitrogen absorbed by rice plant was similar to the relation between the number of secondary rachis branches per unit area and the amount of nitrogen absorbed by rice plant. 4. In treatments which were nearly equal in the number of spikelets per unit area, the more amount of nitrogen absorbed by the time of neck node differentiation were the more number of panicles and primary rachis branches per unit area, but the less numder of secondary rachis branches per unit area and number of spikelets per panicle. 5. Nitrogen contents in leaf blades in each stage did not directly affect the components of the number of spikelets per unit area, but only in cases where the nitrogen contents were correlated with the amount of nitrogen absorbed the nitrogen contents affected the components of the number of spikelets per unit area.