Analysis of Yield-Determining Process and Its Application to Yield-Prediction and Culture Improvement of Lowland Rice. : LXV. Meaning of the application of organic fertilizer on maximizing the yield of lowland rice.

摘要

For maximizing the yield of rice it is quite necessary to obtain high percentages of fully ripened grains under the condition in which too many spikelets per unit area have been borne. Conducting many experiments for long years, Matsushima, one of the authors, realized that it could by no means be achieved without using productive soil, but recently he noticed an idea that it might be achieved not by using any productive soil, but by controlling growth habit (i. e., shortening the lengths of upper 3 or 4 leaf-blades and those of inter-nodes for avoiding the mutual shading of individual leaves) and by increasing the rate of carbon assimilation per unit leaf-area after heading. The authors, therefore, tried to maximize the yield by growing rice plants by water-culture under community conditions, and compared them with those grown in ordinary paddy fields in which a large amout of compost was applied. (By using water-culture, one can easily control the growth habit of rice plants at any growth stage by increasing or decreasing the concentration of nitrogen in the solution.) As a result of it, the rice plants grown by water-culture yielded the amount of 101.6 kg and 77.2 kg of kernels (brown rice) per are, while those grown in paddy fields produced only 57.6 kg at the most. In the present experiment a main control of growth habit was done by decreasing the nitrogen concentration in the solution or taking off nitrogen from the solution during the period from 41 days to 20 days before heading, making the plants short in the lengths of upper 3 or 4 leaf-blades and those of inter-nodes and also thick in the thickness of leaf-blades. On the basis of these facts, the authors concluded the meaning of the application of organic fertilizer as follows; i. e., under the condition of no harmful effects caused by decomposing organic matters in soil being found, organic fertilizers (1) supply the necessary and sufficient amount of all kinds of nutrient elements to the plants through their whole lives, and (2) act as a "buffer" not to supply nitrogen to an excess during the period in which the lengths of upper 3 or 4 leaf-blades and those of inter-nodes are determined.