持续秸秆还田减施化肥对水稻产量和氮磷流失的影响

目的] 探究持续性秸秆还田减施化肥对水稻产量和氮磷随径流流失的影响，为当地农业资源循环再利用和防控农业面源污染提供科学依据。方法] 在四川省广汉市开展连续3 a (2018—2020年)的田间小区试验，设置常规施肥处理(T₁)和秸秆还田+常规施肥减氮28.57%，减磷25.11%(T₂)2种施肥方式，分别测定了地表径流中氮磷浓度、流失量，水稻秸秆、籽粒的产量和氮磷吸收量、水稻收获时土壤养分。结果] 随着秸秆还田年限的增加，T₂可达到显著的增产效果，其中2020年T₂比T₁增产16.93%。与T₁相比，T₂的总氮和硝态氮流失量分别增加6.25%～14.97%，6.99%～15.03%，可溶性总氮、总磷和可溶性总磷流失量分别降低0.94%～6.03%，4.66%～10.32%和5.77%～21.15%。土壤中全磷、速效磷、硝态氮和铵态氮含量的年际变化显著(p<0.05)。与T₁相比，T₂处理显著降低了土壤8.79%的全磷和30.56%的速效磷。结论] 持续秸秆还田与减施化肥在保证作物产量的同时，减少了化肥投入量，降低了磷素的径流流失量，但增加了氮素径流流失的风险，在实际农业生产中应进一步优化处理。

Effects of Continuous Straw Returning Combined with Reduced Fertilizer Application on Rice Yield and Loss of Nitrogen and Phosphorus

Objective] The effects of straw returning combined with reduced chemical fertilizer application on rice yield and nitrogen and phosphorus losses with runoff were studied in order to provide a scientific basis for the recycling and reuse of local agricultural resources and the prevention and control of agricultural non-point source pollution.Methods] A three-year (2018-2020) field plot experiment was conducted that included two treatments:conventional fertilization (T₁), and straw returning + conventional fertilization reduced by 28.57% for nitrogen and 25.11% for phosphorous (T₂). The concentrations and losses of nitrogen and phosphorus in farmland surface runoff, yield, nitrogen and phosphorus uptake by rice straw and grain, and soil nutrients at harvest were determined.Results] As the number of straw returning years increased, T₂ achieved a significant increase in yield. Compared with T₁, the yield of T₂ increased by 16.93% in 2020. Compared with T₁, the loss of the total nitrogen and NO^-₃-N for T₂ increased by 6.25%~14.97% and 6.99%~15.03%, respectively. The loss of the soluble total nitrogen, the total phosphorus, and the soluble total phosphorus for T₂ was 0.94%~6.03%, 4.66%~10.32%. and 5.77%~21.15%, respectively, lower than observed for T₁. The interannual changes of total phosphorus, available phosphorus, nitrate nitrogen, and ammonium nitrogen in soil were significant (p<0.05). Compared with T₁, T₂ significantly reduced soil total phosphorus by 8.79% and available phosphorus by 30.56%.Conclusion] Continuous straw returning combined with reduced chemical fertilizer application ensured the crop yield and reduced the input of chemical fertilizer and the loss of phosphorus in farmland runoff, but increased the risk of nitrogen runoff loss. Therefore, the continuous straw-returning system should be further optimized in actual agricultural production.