控释尿素对环洞庭湖区双季稻吸氮特征和产量的影响

缓控释肥料应用于我国水稻生产中,对化肥使用量零增长和农业可持续发展具有重要推动作用。本研究以连续在湖南进行6年(2013—2018年)的双季稻控释尿素施用试验为研究平台,分析控释尿素施用下环洞庭湖区早晚稻主要生育期地上部氮素累积、氮素阶段吸收速率与氮素利用的关系,探究控释尿素减施对水稻持续稳产增产的原因。结果表明:早稻各施氮处理均有1次明显的氮素阶段吸收速率峰值,控释尿素(controlled-release urea,CRU)处理氮素吸收相对延后,氮素累积主要在幼穗分化始期至抽穗期阶段,占生育期总量的35.31%~42.33%,其次为始分蘖期至幼穗分化始期和抽穗期至乳熟期。晚稻于始分蘖期至幼穗分化始期和抽穗期至乳熟期出现2次明显的氮素阶段吸收速率峰值,均以1.0 CRU(等氮量控释尿素)处理峰值最高;始分蘖期至幼穗分化始期、抽穗期至乳熟期水稻大量吸收氮素,累积增量分别占35.92%~40.52%和23.05%~24.58%。控释尿素还能显著提高双季稻产量,早晚稻分别以0.9 CRU(控释尿素减氮10%)和0.8 CRU(控释尿素减氮20%)处理最佳,控释尿素减施的晚稻增产效果优于早稻,且显著提高早晚稻氮肥吸收利用率、农学利用率和偏生产力。CRU处理早晚稻产量与幼穗分化始期、抽穗期、乳熟期、腊熟期氮素累积量和有效穗数均呈极显著正相关,且晚稻产量与穗长呈显著正相关;早晚稻幼穗分化始期氮素累积量与氮肥农学利用率、生理利用率呈显著负相关,氮肥偏生产力与早稻幼穗分化始期、抽穗期、乳熟期和腊熟期氮素累积量呈极显著或显著负相关,与晚稻抽穗期氮素累积量呈显著负相关。因此,控释尿素施用使水稻氮素阶段吸收速率、地上部氮素累积后延,有利于后期生殖生长及籽粒结实,显著提高双季稻产量及氮肥利用效率。结合双季稻吸氮特征和籽粒产量,建议环洞庭湖区早稻采用释放期较短的控释尿素或配合速效氮肥施用,进一步实现增产。

Effects of controlled-release urea on nitrogen uptake characteristics and yield of double-cropping rice around Dongting Lake area

The application of slow-and controlled-release fertilizer in rice production plays an important role in promoting the zero growth of fertilizer use and the sustainable development of agriculture in China.In this study,six consecutive years from 2013 to 2018 of controlled-release urea application in double-cropping rice in Hunan province were used to analyze the relationship between N uptake rate and N utilization in the above part of early-and late-rice in the main growth period by controlled-release urea application around the Dongting Lake district,and to explore the reasons for the sustained and stable yield increase of controlled-release urea on rice.The results showed that there was an obvious peak of N uptake rate in each stage of early rice by different N treatments,while N uptake in controlled-release urea(CRU)treatment was relatively delayed.And N accumulation was mainly from panicle initiation stage to heading stage,accounting for 35.31%–42.33%,followed by tillering stage to young panicle differentiation stage and heading stage to milk stage.Two obvious peaks of N uptake rates occurred in late rice from tillering stage to panicle initiation stage and from heading stage to milk stage,and the peak value was the highest at 1.0 CRU treatment.Large amount of N uptake from tillering stage to young panicle differentiation stage and heading stage to milk stage accounted for 35.92%–40.52%and 23.05%–24.58%of total amount of the whole growing period,respectively.Controlled-release urea could also significantly increase the yield of double-cropping rice,especially in early-and late-rice were treated with 0.9 CRU and 0.8 CRU respectively,and the yield increase of late rice was better than that of early rice with reduced application of controlled-release urea,and the N absorption efficiency,N agronomic efficiency and N partial productivity of earlyand late-rice were significantly improved.The yield of early-and late-rice treated by CRU was significantly positively correlated with N accumulation and effective panicle number at panicle initiation stage,heading stage,milk stage and waxen stage,and the yield of late rice was significantly positively correlated with panicle length.The N accumulation of early and late rice at the panicle initiation stage was significantly negatively correlated with the agronomic and physiological rates of N fertilizer.The N partial productivity was significantly or significantly negatively correlated with the N accumulation of early rice at the panicle initiation stage,heading stage,milk stage and waxen stage,and significantly negatively correlated with the N accumulation at the heading stage of late rice.Therefore,application of controlled-release urea delayed the N uptake rate and N accumulation in the aboveground part of rice,which was beneficial to the later reproductive growth and seed setting,and could significantly improve the yield and nitrogen utilization efficiency of double-cropping rice.Combined with N absorption characteristics and grain yield of double-cropping rice,it was suggested that controlled release urea with a short release period should be used for early rice around the Dongting Lake area or applied with quick-availability N fertilizer to achieve further increase in yield level.