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The extracellular enzyme plays a crucial role in nitrogen (N) conversion. Soil colloid serves as an important transporter of N transport in hydrological processes. This study investigated soil colloid-mediated N loss co-transporting with soil extracellular enzymes. Five simulated rainfall experiments were conducted under four tillage treatments in a purple sloping farmland in Sichuan, China. The N concentrations, soil mineral colloids, and four carbon (C), N and phosphorus (P) acquisition extracellular enzymes (βG, AP, NAG, and LAP) in surface runoff and interflow were measured. The results showed that cross-slope tillage with straw returning practices significantly reduced the concentrations of TN, PN, NH4+, and DON in surface runoff. The activities of N and P acquisition enzymes in interflow were higher than in surface runoff, while C acquisition enzymes showed the opposite trend. The BG and AP enzymes dominated in surface runoff, while AP and NAG dominated in interflow. The concentrations of fine soil mineral colloids (SMC, φ |
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