秸秆连续还田对水稻产量和氮素利用的影响

为明确秸秆还田比例对水稻产量和氮素利用的影响，于2019—2021年生长季在贵州省思南县塘头镇进行了田间小区定位试验。试验设6个处理：CK为不施肥，S₀为常规施肥，S₁（常规施肥+秸秆还田5 t/hm²）、S₂（常规施肥+秸秆还田10 t/hm²）、S₃（常规施肥+秸秆还田15 t/hm²）、S₄（常规施肥+秸秆还田20 t/hm²）。结果表明：2019—2021年秸秆还田均以S₃处理产量最高，分别比S₀处理增加20.16%、8.66%、14.40%，2019年产量增幅最高。造成产量差异的原因是秸秆还田提高了水稻有效穗数、穗粒数、千粒重和结实率，进而显著提高产量。秸秆还田与水稻籽粒产量的拟合分析表明，在籽粒产量最高处秸秆还田量为15.43 t/hm²。秸秆还田均能提高年份间氮肥偏生产力和氮素收获指数，在2019年，氮肥偏生产力以S₃处理最高，而氮素收获指数以S₄处理最高，分别比S₀增加42.81%和24.30%；在2020年以S₃处理最高，分别比S₀增加55.98%和22.61%；在2021年以S₃处理最高，分别比S₀增加21.75%和15.88%。秸秆还田增加了年份间氮素生理利用率，均以S₃处理最高，比S₀处理分别增加72.97%、76.14%和52.98%，且年份和秸秆还田处理这2个因素对氮素生理利用率和氮素农学效率有极显著的提高。因此，综合水稻产量、秸秆还田拟合结果以及氮素利用率，秸秆还田量以S₃处理较为适宜。

Effects of Continuous Straw Returning on Rice Yield and Nitrogen Utilization

To clarify the impact of straw returning ratio on rice yield and nitrogen utilization, a field plot positioning experiment was conducted in Tangtou Town, Sinan County of Guizhou Province during the rice growing season from 2019 to 2021. Six treatments were set up in the experiment: CK was no fertilizer, S₀ was conventional fertilizer, S₁ was conventional fertilizer + straw returning 5 t/hm², S₂ was conventional fertilizer + straw returning 10 t/hm², S₃ was conventional fertilizer + straw returning 15 t/hm², and S₄ was conventional fertilizer + straw returning 20 t/hm². The results showed that from 2019 to 2021, the yield of S₃ treatment was the highest, increased by 20.16%, 8.66% and 14.40% respectively compared with that of S₀ treatment, and the yield increase in 2019 was the highest. The reason for the yield difference was that straw returning to field improved the number of effective panicles, the number of grains per panicle, 1000-grain weight and seed setting rate of rice, and then significantly increase the yield. The fitting analysis of straw returning and rice grain yield showed that the highest grain yield was achieved by straw returning amount of 15.43 t/hm². Straw returning could improve the nitrogen partial factor productivity and nitrogen harvest index between years. In 2019, the nitrogen partial factor productivity of S₃ treatment was the highest, while the nitrogen harvest index of S₄ treatment was the highest, which were 42.81% and 24.30% higher than those of S₀ respectively. In 2020, the nitrogen partial factor productivity and nitrogen harvest index of S₃ treatment were the highest, with an increase of 55.98% and 22.61% over those of S₀ treatment respectively; and in 2021, the nitrogen partial factor productivity and nitrogen harvest index of S₃ treatment were also the highest, with an increase of 21.75% and 15.88% over those of S₀ treatment, respectively. Straw returning increased the physiological utilization rate of nitrogen between years, and S₃ treatment had the best effect, with an increase of 72.97%, 76.14% and 52.98% respectively compared with that of S₀ treatment from 2019 to 2021. Moreover, year and straw returning treatment significantly improved the physiological utilization rate of nitrogen and agricultural efficiency of nitrogen. Therefore, considering rice yield, straw returning fitting results and nitrogen utilization rate, S₃ treatment is more suitable for straw returning.