翻耕除草对不同坡长下紫色土氮磷流失的影响

为揭示自然降雨下翻耕除草和坡长对紫色土氮、磷流失的影响,通过野外设置径流小区(2个坡面:翻耕除草与自然恢复;3种坡长:20,40,60 m,共9个小区),定位监测研究不同处理下产流产沙及氮、磷流失特征。结果表明,同一坡面不同坡长间产流产沙差异不显著(P0.05);同一坡长不同坡面处理小区的径流量、产沙量差异极显著(P0.01)。与翻耕除草相比,自然恢复坡面20,40,60 m坡长小区径流量分别减少77.55%,62.62%,79.56%,产沙量分别减少85.21%,94.97%,96.25%。仅在40 m坡长下,不同坡面处理径流中DN、DP流失量差异不显著(P0.05),其他坡长DN、DP流失量差异显著(P0.05);各坡长不同坡面处理下泥沙中TN、TP流失量差异极显著(P0.01)。与翻耕除草相比,自然恢复坡面处理径流中DN、DP流失量分别减少75.13%,80.22%,泥沙中TN、TP流失量分别减少96.07%,96.38%。在翻耕除草坡面处理下,降雨强度与径流量、产沙量及泥沙中的TN和TP流失量呈极显著幂函数关系;在自然恢复坡面处理下,上述关系均不显著。研究结果可为紫色土氮、磷流失及面源污染防治等提供理论参考依据。

Effects of Tillage and Weeding on Nitrogen and Phosphorus Losses of Purple Soil at Different Slope Lengths

To clarify the influences of tillage and weeding and slope length on the losses of nitrogen (N) and phosphorous (P) under natural rainfall in purple soil area,9 plots combined with two land disturbances (tillage and weeding and natural restoration) and three slope lengths (20,40,and 60 m) were established to compare the runoff and sediment yield,and N and P losses. The results showed that slope length had no remarkable effect on the runoff and sediment yield under the same land condition (P>0.05),while tillage and weeding plots significantly differed the runoff and sediment yield from natural-restored plots under the same slope length (P<0.01). Natural-restored plots of 20,40,60 m respectively reduced runoff by 77.55%,62.62%,79.56%,and sediment yield by 85.21%,94.97%,96.25%,compared with the tillage and weeding plots. There were significant effects of land disturbance on runoff-related DN and DP losses under 20 and 60 m plots (P<0.05) and on sediment-related TN and TP losses across all plot lengths (P<0.01). Natural-restored plots could reduce the losses of DN and DP in runoff by 75.13% and 80.22%,and the losses of TN and TP in sediment by 96.07% and 96.38%,respectively. Rainfall intensity had significantly power relationship with runoff and sediment yield,and TN and TP losses with sediment-related under tillage and weeding plots,but there was no significant relationship under natural-restored plots. The results can provide theoretical reference for N and P losses and non-point source pollution control in the purple soil area.