Effects of Drainage after Submerged Direct-Seeding on the Effectiveness of Fertilized Nitrogen and the Growth and Yield of Rice Plants

[摘要] Drainage after seeding has recently been practiced in general for the improvement of seedling emergence in submerged direct-seeding rice(Oryza sativa L.)cultivation. We examined the relationship between water management after direct-seeding and the effectiveness of fertilized nitrogen to clarify the effects of drainage on the growth and yield of rice. It was confirmed that the drainage after seeding improved the seedling emergence rate and stimulated the initial growth of the seedling. When controlled release fertilizer(LPl00)was applied as basal dressing, water management after seeding had no effect on the growth and yield. However, when ammonium sulfate was applied, the yield was reduced by the drainage after seeding, due to the decrease in nitrogen uptake of rice at the panicle initiation stage, and resulting reduction in the number of spikelets. In this case, nitrogen uptake seemed to be reduced because nitrogen uptake in the early growth stage was increased by the increase in initial growth and tillering and because the content of ammonium nitrogen in soil was reduced by nitrification of the fertilized nitrogen during drainage. These results showed that the suppression of nitrogen uptake at the initial growth stage and the avoidance of nitrogen deficiency at the intermediate growth stage, are important to stabilize not only seedling emergence but also growth and yield for the management of drainage after seeding.

[学科分类] 农业科学（综合）

[关键词] Drainage;出芽;Growth;水稲;Nitrogen fertilizer;生育;Nitrogen uptake;施肥窒素;Rice;湛水直播;Seedling emergence;窒素吸収;Submerged direct-seeding;落水管理