【摘要】 【目的】紫色土坡耕地耕层浅薄，结构稳定性差，氮素流失严重，影响作物产量。在典型紫色土区开展田间试验，研究优化施肥配合秸秆还田防治紫色土区坡耕地农业面源污染和提高作物产量的效果。【方法】2019—2021年在重庆市典型紫色土区坡耕地上进行田间试验，种植制度为高粱-油菜轮作。设置常规施肥（CK）、优化施肥（IFT）和优化施肥+秸秆覆盖还田（IFT+SMT） 3个处理，调查了高粱、油菜产量及次降雨径流中的全氮（TN）、硝态氮（NO3^--N）和铵态氮（NH4⁺-N）含量。【结果】与CK处理相比，2019年IFT+SMT和IFT处理油菜产量显著增加了30.70%、26.34%,2020年分别增加了32.03%、27.48%（P<0.05）。大雨及以上等级降雨事件的径流量以及径流液中的TN、NO₃^--N和NH₄⁺-N浓度和流失量总体高于小雨、中雨。同样降雨条件下，IFT+SMT处理的径流深和径流系数多低于CK和IFT处理。2019—2021年，IFT+SMT处理的NO3--N平均浓度较CK处理均有所减少，但差异不显著。同一年份下，不同处理径流液间的TN、NO₃^--N和NH₄⁺-N的平均浓度均不存在显著性差异。在不同年份下仅有IFT+SMT处理的NH₄⁺-N浓度存在显著性差异（P<0.01）,2021年NH4⁺-N浓度分别比2019和2020年降低了39.55%和49.70%（P<0.01）。与CK处理相比，2019年IFT+SMT处理的TN和NO3^--N年累积流失量分别显著降低了10.19%和17.72%（P<0.05）,2021年的TN、NO3^--N和NH4⁺-N年累积流失量分别显著降低了21.65%、19.12%和33.24%（P<0.01）；然而，2020年IFT+SMT处理的TN、NO3^--N和NH4⁺-N年累积流失量较CK处理分别显著增加了39.56%、51.10%和40.42%（P<0.01）。IFT+SMT处理能有效减少NO3^--N流失。高粱、油菜产量均与径流量、NH4⁺-N年累积流失量呈显著正相关（P<0.05）。【结论】优化施肥+秸秆覆盖还田处理的径流系数、全氮和NO₃^--N浓度及流失量均有降低，尤其对NO₃^--N流失的阻控效果较为突出，此外，该处理还显著提高了油菜和高粱产量，提高了作物对氮素的吸收利用量，从而有效减少氮素流失。更多还原

【Abstract】 【Objectives】Purple sloping cropland is characterized by shallow tillage,poor structural stability and substantial nitrogen loss,which affects crop yields.We conducted a field experiment of optimized fertilization in conjunction with straw return to the field in a typical purple soil,to determine its effectiveness in preventing agricultural non-point source pollution,and improving crop yields on purple sloping croplands.【Methods】The field experiment was conducted from 2019-2021 in a typical purple sloping cropland of Chongqing,with the cropping system of sorghum-rape rotation.Three treatments of conventional fertilization (CK),optimized fertilization (IFT) and optimized fertilization+straw return (IFT+SMT),were set up to investigate the yields of sorghum and rape,and the contents of runoff total nitrogen (TN),nitrate nitrogen (NO3~--N),and ammonium nitrogen (NH4~+-N),and to analyze the nitrogen loss characteristics.【Results】The rape yield was significantly increased by 30.70%and 26.34%in 2019 and 32.03%and 27.48%in 2020 for IFT+SMT and IFT treatments,respectively,compared with CK (P<0.05).Heavy and above class rainfall events generally resulted in higher runoff volumes and elevated concentrations and losses of TN,NO3~--N,and NH4~+-N in runoff compared to light and moderate rainfall events.Under the same rainfall conditions,the IFT+SMT treatment exhibited lower runoff depth and runoff coefficient compared to the CK and IFT treatments.In 2019-2021,the NO3~--N concentrations of the IFT+SMT treatments all decreased compared to CK,but the differences were not significant.The concentrations of TN,NO3~--N,and NH4~+-N in runoff were not significantly different among treatments in the same year.Significant differences in NH4~+-N concentrations existed only for the IFT+SMT treatments under different years (P<0.01),the NH4~+-N concentrations in 2021 being 39.55%and 49.70%lower than those in 2019 and 2020,respectively (P<0.01).In 2019,compared to CK,the annual cumulative loss of TN and NO3~--N was significantly reduced by 10.19%and 17.72%for IFT+SMT treatment,respectively (P<0.05).In 2021,compared to CK,the annual cumulative loss of TN,NO3~--N,and NH4~+-N in the IFT+SMT treatment was significantly reduced by21.65%,19.12%,and 33.24%,respectively (P<0.01).However,the annual cumulative TN,NO3~--N,and NH4~+-N losses in 2020 were significantly increased in the IFT+SMT treatment compared to CK by 39.56%,51.10%,and40.42%,respectively (P<0.01).The IFT+SMT treatment was effective in reducing NO3~--N losses.Sorghum and rape yields were all significantly and positively correlated with runoff and annual cumulative NH4~+-N losses (P<0.05).【Conclusions】The runoff coefficient,TN and NO3~--N concentration and loss were reduced in the IFT+SMT treatment,especially the blocking and controlling effect on NO3~--N loss was more prominent,in addition,the treatment significantly increased the yield of rape and sorghum,increased crop uptake and utilization of nitrogen,thus effectively reducing nitrogen loss.更多还原