[Characteristics of nutrient loss by runoff in sloping arable land of yellow-brown under different rainfall intensities].

In order to investigate the loss characteristics of N and P through surface flow and interflow under different rainfall intensities,a field experiment was conducted on the sloping arable land covered by typical yellow-brown soils inXiangxi River watershed by artificial rainfall.The results showed that the discharge of surface flow,total runoff and sediment increased with the increase of rain intensity,while the interflow was negatively correlated with rain intensity under the same total rainfall.TN,DN and DP were all flushed at the very beginning in surface flow underdifferent rainfall intensities;TP fluctuated and kept consistent in surface flow without obvious downtrend.While TN,DN and DP in interflow kept relatively stable in the whole runoff process,TP was high at the early stage,then rapidly decreased with time and kept steady finally.P was directly influenced by rainfall intensity,its concentration in the runoff increased with the increase of the rainfall intensity,the average concentration of N and P both exceeded the threshold of eutrophication of freshwater.The higher the amount of P loss was,the higher the rain intensity.The change of N loss was the opposite.The contribution rate of TN loss carried by surface flow increased from 36.5% to 57.6% with the increase of rainfall intensity,but surface flow was the primary form of P loss which contributed above 90.0%.Thus,it is crucial to control interflow in order to reduce N loss.In addition,measures should be taken to effectively manage soil erosion to mitigate P loss.The proportion of dissolved nitrogen in surface flow elevated with the decrease of rainfall intensity,but in interflow,dissolved form was predominant.P was exported mainly in the form of particulate under different rainfall intensities and runoff conditions.