不同坡度坡耕地土壤氮磷的流失与迁移过程

The Processes of Nitrogen and Phosphorus Loss and Migration in Slope Cropland Under Different Slopes

采用人工模拟降雨试验研究不同坡度的土壤侵蚀程度,分析了土壤养分在不同坡度（5°,10°,15°,20°,25°）随坡面径流流失及水分入渗向下迁移的动态变化过程和机制。结果表明,在恒定降雨强度下,初始产流10min内,产流产沙量随时间迅速递增,随后缓慢增加并逐渐趋于稳定,总产流量大小为15°〉10°〉20°〉5°〉25°;10°总产沙量最大,15°和20°总产沙量相近,5°和25°总产沙量接近。不同坡度条件下总产流量和总产沙量随坡度的变化趋势均可用二次函数拟合,相关系数R2为0.65。10°~15°坡度之间存在一个对径流中养分浓度变化有显著影响的转折点。硝态氮在湿润层内的迁移过程用幂函数描述,铵态氮在湿润层内的浓度变化用三次多项式拟合,速效磷浓度在湿润层内随深度变化并不明显;硝态氮、铵态氮总流失量随坡度的变化趋势符合二次多项式变化,相关系数R2分别为0.91和0.77。20°时水溶性磷流失总量最大,为15°坡面的1.61倍。径流中初始养分浓度主要受养分在径流中溶解度的影响,在产流后期,土壤流失量对径流养分浓度的影响程度加大。

Took artificial simulation rainfall to study soil erosion degree in different slopes（5,10,15,20,25degrees）and analyzed process and mechanism of dynamic changes of the soil nutrient loss with runoff erosion and migration with water infiltration in different slopes.The results showed that under the constant rainfall intensity the runoff and sediment yield increased rapidly within the initial 10 minutes then increased slowly and gradually stabilized.The order of output flow was 15degree〉10degree〉20degree〉5degree〉25degree.10 degree total sediment yield was maximum,15 degree and 20 degree of the total sediment yield were similar,5degree and 25 degree of the total sediment yield were close.Under the conditions of different slopes,the trend with the slope of total runoff and total sediment yield could be fitted with a quadratic function and the correlation coefficient R2 was 0.65.And there was a critical value that had a significant effects on nutrient concentrations of runoff under slope degrees between 10 degree and 15 degree.In addition the migration process of nitrate nitrogen in wet layer could be described in the power function and the concentration change of ammonium nitrogen in wet layer was in agreement with cubic polynomial curve,while there was no significant change of the available P concentration with depth under the wet layer.The trend with the slope of the total loss amount of nitrate and ammonium were quadratic polynomial change,the correlation coefficient R2 was 0.91 and 0.77 respectively.The total amount of water-soluble phosphorus loss was maximum on20 degree,it was 1.61 times of 15 degree slope.Initial nutrient concentration in runoff influenced mainly by nutrient solubility and the quantity of soil loss had more effects on the nutrient concentration in the late runoff.