不同播期直播稻氮素吸收、利用效率的差异

Differences of nitrogen absorption and utilization efficiency in direct seeding rice with different sowing date

以中熟中粳、迟熟中粳和早熟晚粳3种类型具有代表性的4个水稻品种为材料,通过大田分期播种试验,对直播稻产量、氮素积累量、氮素吸收速率和氮素利用效率的差异及其之间的相互关系进行系统的比较研究。结果表明:随播期的推迟,产量呈显著或极显著的下降趋势,主要是由于每穗颖花数与结实率的下降,穗数与千粒重变化不大;拔节期植株含氮率表现为逐渐上升的趋势,抽穗期和成熟期均表现为逐渐下降的趋势;拔节期、抽穗期和成熟期的植株吸氮量均呈显著的下降趋势;拔节前氮素吸收总量呈逐渐下降的趋势,其占植株总吸收量的比例呈逐渐上升的趋势,拔节至抽穗期和抽穗至成熟期的氮素阶段吸收量及其占总吸收量的比例均呈逐渐下降的趋势;播种至拔节期阶段的氮素吸收速率呈上升趋势,而拔节至抽穗期、抽穗至成熟期呈显著或极显著的下降趋势;氮素吸收利用率、农学利用率、生理利用率和偏生产力均呈不同程度的下降趋势。相关分析表明,产量与氮素吸收量、吸收速率及氮素利用效率的关系除拔节至抽穗期的氮素阶段吸收速率外均呈显著或极显著的正相关。在试验条件下,相对于迟播而言,直播稻早播的产量、各个时期的吸氮累积量、各个生育阶段的氮素积累量、拔节后的氮素吸收速率及氮素利用效率均较高。可见,直播稻早播有利于氮素的高效吸收和利用并取得高产。

Field experiments were conducted to compare the differences and relationships among yield, nitrogen（N） accumulation, N uptake rate and N use efficiency, with four representative rice cultivars of three types of early-maturing late japonica rice,late-maturing medium japonica rice and medium-maturing medium japonica rice （including japonica con- ventional rice and japonica hybrid rice） as experimental materials directly seeded at different sowing date. The results showed that： along with the delayed sowing date, （1） the yields decreased significantly or very significantly,which was caused by the decline of spikelets per panicle and filled grain percentage, while panicles and 1000-grain weight had a little change; （2） N content in plant increased in jointing stage increased but decreased in heading and maturity stage; （3） N uptake in plant of jointing, heading and maturity showed a significant downward trend; （4） N accumulation before joint- ing decreased,but its ratio to total rised, N accumulation and its ratio to total both from jointing to heading and from heading to maturity showed a gradual downward trend. （5） N uptake rate from sowing to jointing rised, but both from jointing to heading and from heading to maturity showed a significant or very significant downward trend. （6） N recovery N agronomic efficiency, N physiological efficiency and N partial productivity showed a downward trend of different degrees. （7） Correlation analysis indicated that there existed significant or very significant positive correlations betweenyield and N accumulation, N uptake rate and N use efficiency except N uptake rate from jointing to heading. Under the experimental conditions, compared with late sowing, yield, N uptake of every stage, N accumulation of every period, N up- take rate after jointing and N use efficiency of direct seeding rice which sowed early were higher. It was obvious that early sowing of direct seeding rice is in favor of the N efficient absorption and utilization and high yield.