Influence of Drainage on the Growth of Rice Plant in Rice Field. : I) Effect of drainage of surface water on the growth, yield and nutrient uptake of rice plant

Abstract

The experiment was made to evaluate the effect of drainage of surface water on the growth, yield and nutrient uptake of rice plant. Rice plants were grown in both submerged and drained conditions. The water level in the submerged plots was maintained at 5 cm depth through the growing season. In contrast, the drained plots were kept under wet condition (no standing water) from one week after transplanting to harvesting time. Both plots mentioned above included much and less fertilization, each with powdery, granular fertilizer and soybean cake, respectively. The results obtained were as follows. 1) The drained plots, as compared with the submerged plots, generally showed the increased number of tillers in both tillering and booting stages, and the decreased number of panicles at harvest. The weight of dry matter per hill in the drained plot became to be inferior to that in the submerged plot as the rice plant grew, especially in the case of less fertilization. 2) It was found that the amounts of N, P₂O₅, K₂O and SiO₂ absorbed by rice plant were commonly decreased by the draining, but in some cases were temporarily increased at tillering stage. The absorption rate of nutrients of rice plant in the drained plots decreased remarkably in the case of less fertilization. 3) The grain yields in the submerged plots were higher than those in the drained plots, except for the much fertilization plots with granular fertilizer. In general, the reduction of grain yield by the draining were less in the much fertilization than in the less fertilization and less in granular than in powdery and soybean cake. Thus, it is suggested that the reduction of the grain yield in the drained plots are depend chiefly on the decrease of the nutrient uptake of the rice plant at later stage of growth, because the long time drainage decreases availability of N, P₂O₅, SiO₂ etc. in soil.