不同减氮栽培模式对杂交籼稻氮素吸收利用及产量的影响

  【目的】  探索不同减氮栽培模式对水稻氮素吸收利用及产量的调控效应，为水稻减氮高产栽培提供理论依据。  【方法】  选用杂交籼稻品种‘成优981’和‘宜香优2115’为试验材料，以常规高产栽培为对照(湿润灌溉、种植密度20.0×104/hm2、施氮量187.5 kg/hm2，T0)，设3种减氮栽培处理:单一减氮(湿润灌溉、种植密度20.0×104/hm2、减氮10%，T1)，增密减氮(湿润灌溉、种植密度24.0×104/hm2、减氮10%，T2)，控水增密减氮(轻干湿交替灌溉、种植密度24.0×104/hm2、减氮10%，T3)。研究不同减氮栽培模式对水稻根系生长、氮素吸收利用及产量的影响。  【结果】  1)与常规高产栽培(T0)相比，单一减氮栽培(T1)水稻根干重、根系α-NA氧化量、根系伤流强度有显著降低；增密减氮栽培(T2)水稻根干重与T0基本相当，但根系α-NA氧化量、根系伤流强度显著降低；控水增密减氮栽培(T3)在拔节期和抽穗期的水稻根系生长指标与T0差异较小，成熟期多显著高于T0。2)与T0相比，T1在拔节、抽穗、成熟期的氮素积累量多显著降低；T2和T3在拔节、抽穗期的氮素积累量与T0差异较小；抽穗至成熟阶段的氮素积累量、成熟期穗部氮素分配量均为T3>T0>T2>T1；氮肥吸收利用率、农学利用率和偏生产力均表现为T3>T2>T1，且T3上述指标均较T0有所提高。3) 4种栽培模式的水稻产量表现为T3>T0>T2>T1。T1较T0产量降低6.37%，其中有效穗数和穗粒数均显著降低；T2主要降低了穗粒数和千粒重，因而产量也有所降低；T3较T0增产1.78%，主要提高了结实率和千粒重。  【结论】  单一减氮显著降低水稻根系生长量和氮素积累量，进而造成显著减产；增密减氮能有效提高水稻根系生长量和氮素积累量，减少产量损失；控水增密减氮栽培能显著提高水稻中后期根系生理活性和氮素积累量，并促进氮素由营养器官向穗部转运，提高氮肥利用率，实现减氮高产。

Effects of nitrogen-reduction cultivation models on nitrogen accumulation and yield of hybrid indica rice

  【Objectives】  To assess the effects of the cultivation models on nitrogen (N) use efficiency and grain yield of hybrid indica rice under nitrogen-reduction.  【Methods】   The hybrid indica rice cultivar Chengyou 981 and Yixiangyou 2115 were selected as the planting materials. The conventional high-yielding nitrogen application rate (187.5 kg/hm2) with wet irrigation and 20.0×104/hm2 of plant density was set as the control cultivation model or treatment (T0). Other three cultivation models/treatments in the experiment were N-reduction cultivation models: 10% reduction of N application rate with wet irrigation and 20.0×104/hm2 plant density (mono-nitrogen reduction, T1), 10% reduction of N with wet irrigation and 24.0×104/hm2 of plant density (increased density under nitrogen-reduction, T2), and 10% reduction of N with alternate wetting and moderate drying irrigation, and 24.0×104/hm2 of plant density (controlled irrigation and increased density under nitrogen-reduction, T3). The root growth, N absorption and utilization, and grain yield of hybrid indica rice were investigated.   【Results】  1) Compared with the conventional high-yielding treatment (T0), the root dry weight, root α-NA oxidation and root bleeding intensity of rice in T1 were significantly reduced; the root α -NA oxidation and root bleeding intensity decreased significantly in T2; and the root growth indices in T3 were similar to T0 at jointing and heading stages, but significantly higher than T0 at maturity stage. 2) Compared with T0, the N accumulation of rice at jointing, heading and maturity stages in T1 significantly decreased, while the N accumulation at jointing and heading stages in T2 and T3 were slightly different from T0. The N accumulation during heading and maturity stages and N allocation in panicle at maturity stage were T3>T0>T2>T1. The recovery efficiency, agronomic efficiency and partial factor production of N fertilizer were T3>T2>T1, and the indices of T3 were also higher than T0. 3) The rice yield was in the order of T3>T0>T2>T1. T1 decreased yield by 6.37% compared with T0, owning to the significant decrease in effective panicle number and spikelets per panicle. T2 had a lower yield than T0, owing to the decreased effective spikelet number and 1000-grain weight; T3 had a higher yield than T0 by 1.78%, owning to the increased seed setting rate and 1000-grain weight.  【Conclusions】  Reduction of N fertilizer input would significantly inhibit root growth and activity, affect the N uptake and accumulation of rice, and result in significant yield reduction. Increasing densities under nitrogen-reduction could effectively increase the root biomass and N accumulation of rice, but could not offset the yield loss caused by decreased effective spikelet number and 1000-grain weight. Controlled irrigation combined with increased densities and reduced N input could significantly improve root physiological activity at the middle to late stage, N accumulation and translocation from vegetative organs to the panicle of rice, nitrogen use efficiency and yield.