Optimization of fertilization and straw returning on purple sloping croplands effectively increases crop yield and reduces total runoff nitrogen loss
[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 by 21.65％,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％,and 40.42％,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.
万方数据
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