秸秆还田下寒地水稻实现高产高氮肥利用率的氮肥运筹模式

  【目的】  秸秆还田是东北寒地水稻种植区培肥土壤的重要措施，研究调整水稻基蘖氮肥与穗氮肥比例，为促进寒地水稻氮肥的合理施用提供科学依据。  【方法】  田间试验于2016、2017年在吉林省进行，供试水稻品种为吉粳511。上一季水稻收获后，秸秆9000 kg/hm2粉碎至10 cm左右，翻压还田。在总施氮 (N) 量200 kg/hm2不变的前提下，设置5个基蘖肥与穗肥比例处理5∶5 (N 5∶5)、6∶4 (N 6∶4)、7∶3 (N 7∶3)、8∶2 (N 8∶2) 和9∶1 (N 9∶1)，以不施氮肥 (N0) 为对照。在水稻6个生育期调查植株生物量和氮素含量，成熟期测定产量及产量构成因素。计算了氮素积累与转运特征，以及氮素利用效率。  【结果】  与N0处理相比，施氮提高了水稻穗数、穗粒数和结实率，进而显著提高了产量，以N 8∶2处理的水稻产量最高。水稻返青期至拔节期，氮积累量随基蘖氮肥占总施氮量比例的增加而增加，而齐穗期至成熟期阶段则表现为随基蘖氮肥占总施氮量比例的增加先增后减，氮素积累总量以N 8∶2处理最高。施氮显著提高了氮素转运量和齐穗后积累氮素对籽粒氮积累量贡献率，其中氮素转运量随基蘖氮肥占总施氮量比例的增加而增加，而齐穗后积累氮素对籽粒氮积累量贡献率随基蘖氮肥占总施氮量比例的增加先增后降，以N 8∶2处理最高。随基蘖氮肥占总施氮量比例的提高，氮素回收率、农学利用率、偏生产力和生理利用率均呈现先增后减趋势，均以N 8∶2处理最高。相关分析结果表明，水稻齐穗期前后氮素积累量与水稻产量均呈显著或极显著正相关 (r = 0.8943～0.9476)，其中水稻齐穗后氮积累量与产量的相关性高于齐穗前。  【结论】  在秸秆还田条件下，基蘖氮肥与穗氮肥比例为8∶2最有利于提高水稻齐穗期至成熟期氮积累量，促进氮素向籽粒的转运，使水稻产量和氮素利用效率协同提高。因此，在本试验条件下，总施氮量200 kg/hm2，基蘖肥与穗肥比例为8∶2的施氮制度是优化水稻氮素积累特性及获得高产的理想运筹模式。

Nitrogen fertilizer management for high nitrogen utilization efficiency and rice yield under straw incorporation in a cold region

  【Objectives】  In the cold rice-growing region, straw incorporation is a popular technology for sustaining soil fertility. Here, we studied the allocation of N fertilizer ratio for basal-tillering and panicle stage of rice production to provide a scientific basis for the rational application of N fertilizer in this region.  【Methods】  Field experiments were conducted in 2016 and 2017 in Jilin Province, using rice cultivar Jijing 511 as test materials. In the previous year, 9000 kg/hm2 rice straw was cut to about 10 cm long and buried into the soil with a plough. Using a total of 200 kg/hm2 N fertilizer, five basal-tillering/panicle application ratios were set up, including 5∶5 (N 5∶5), 6∶4 (N 6∶4), 7∶3 (N 7∶3), 8∶2 (N 8∶2), 9∶1 (N 9∶1), and no N fertilizer application (N0) used as the control. The rice plant’s dry matter and N content were analyzed in 6 growing stages, and yield and its components were investigated at harvest. The N accumulation dynamics, translocation characteristics, and N utilization efficiency were calculated.  【Results】  Compared with N0, N fertilizer application improved panicle number, grain number per panicle, and seed-setting rate of rice, and significantly increased yield as a result. Rice yield reached the highest in the N 8∶2 treatment. N accumulation from returning green stage to jointing stage increased with increased N ratio in basal-tillering stage, but that from the full heading stage to maturity stage increased first and then decreased, with the highest value in N 8∶2 treatment. N fertilizer application significantly increased N translocation and accumulation in the rice grains after the full heading stage. N translocation increased with an increased ratio of N in the basal-tillering stage. Moreover, accumulated N in the rice grains at the full heading stage increased firstly and then decreased, reaching the highest in the N 8∶2 treatment. Correspondingly, all the N recovery efficiency, agronomic efficiency, partial factor productivity, and physiological efficiency reached the highest in the N 8∶2 treatment. Correlation analysis showed a significant positive relationship between yield and N accumulation at the full heading stage (r = 0.8943?0.9476). However, after the full heading stage, the correlation coefficient was higher than the value recorded before this stage.  【Conclusions】  Under straw incorporation, the 8∶2 N fertilizer treatment for basal-tillering and panicle stage of rice production had the highest N accumulation from the full heading stage to maturity stage, increased N translocation to grains, improved yield, and N utilization efficiency. Therefore, under the experimental conditions, we recommend using 200 kg/hm2 N fertilizer at 8∶2 for basal-tillering and panicle stage of rice production to optimize N accumulation characteristics and improve yield.