典型农作措施对沙溪庙组壤质紫色土坡耕地径流氮流失的影响

明确典型农作措施对紫色土坡耕地径流氮(N)流失的影响可为优化面源污染防控措施提供科学依据。基于2019—2021年沙溪庙组发育的壤质紫色土坡耕地不同降雨等级次降雨产流事件，分析了常规施肥(CK),优化施肥(T1)和优化施肥+秸秆还田(T2)措施下径流、径流中总氮(TN)、硝态氮(NO₃-N)及铵态氮(NH₄-N)流失浓度和流失量的变化特征。结果表明，与CK相比，T1和T2的径流深分别减小了4.24%、12.71%,但减小程度不显著(P>0.05);CK与T1的径流系数相等，且比T2增加了12.5%(P>0.05);相比CK,T1和T2的TN浓度增加了19.35%、25.8%(P>0.05),TN流失量则均增加了11.54%(P>0.05),表明T1和T2的施用也有增加土壤N流失的潜在风险。与中雨、大雨和大暴雨事件相比，暴雨事件的径流深分别增加了6.5%—191.11%(P<0.05),而TN、NO₃-N及NH₄-N的流失量分别增加106.38%—177.14%(P>...

Effects of representative agricultural measures on runoff nitrogen loss in loamy purple sloping croplands originating from Shaximiao Group

Interpreting the effects of representative agricultural measures on runoff nitrogen (N) loss in purple soil sloping croplands can help to provide the scientific basis for optimizing the preventive and control measures of non-point source pollution. During 2019-2021, in accordance with the recorded rainfall events grouped into different rainfall categories on the loamy purple soil sloping cropland originating from Shaximiao Group, the characteristics of runoff yield, the concentrations and losses of total nitrogen (TN), nitrate nitrogen (NO₃-N) and ammonium nitrogen (NH₄-N) in runoff under three representative agricultural measures including conventional fertilization (CK), optimized fertilization (T1), and optimized fertilization+straw returning (T2) measures were carefully examined. The results showed that compared with CK, the runoff depth decreased by 4.24% and 12.71% for T1 and T2, respectively, though these changes were not significantly different (P>0.05). The runoff coefficients in CK and T1 were equal and both 12.5% higher than that in T2 (P>0.05). TN concentration increased by 19.35% and 25.8%, and its loss increased by 11.54% in T1 and T2, respectively, compared with CK (P>0.05), indicating that the applications of T1 and T2 also have a potential risk of increasing soil N loss. Compared with moderate rain, heavy rain and large rainstorms, the runoff depth under rainstorms increased by 6.5%-191.11% (P<0.05), and the losses of TN, NO₃-N, and NH₄-N under rainstorms also increased by 106.38%-177.14% (P>0.05), 32.14%-360% (P<0.05), and 55.56%-600% (P<0.05), respectively. Additionally, compared with rainfall amount and runoff coefficient, runoff depth showed relatively stronger correlations with the study N loss variables (R²=0.32-0.76), indicating that runoff depth may be more suitable to describe the dynamics of N loss when developing the prediction models. Our results imply that the risk of soil N retention and inorganic N migration with runoff should be considered when optimized fertilization and straw returning measures are adopted.