不同耕作方式对紫色土侵蚀及磷素流失的影响

【目的】研究川中丘陵区紫色土零散坡耕地在玉米成熟期由降雨引发的水土流失及磷素流失特征，为该区坡耕地养分流失预测评价、防治以及协调区域土地管理，改善生态环境提供理论依据。【方法】采用人工模拟降雨和微小区试验相结合的方法，在玉米成熟期，对平作、顺坡垄作及横坡垄作3种耕作方式的地块进行人工降雨，降雨强度为1.7 mm?min-1,历时40 min。研究人工降雨对地表侵蚀、壤中流量及其磷素流失的影响。【结果】顺坡垄作地表侵蚀量及磷素流失量均最大，其壤中流及磷素流失最小；横坡垄作地表侵蚀量及磷素流失量最小，而壤中流损失较大。不同耕作方式下壤中流总量虽然较地表径流少，但是其磷素含量却很高，总磷浓度均达到了0.2 mg?L-1,约为地表径流的1.3倍。【结论】紫色土零散坡耕地不易采用顺坡垄作，横坡垄作能很好的控制土壤侵蚀，但在日常耕作管理中需注意对垄的修复保护。在整个侵蚀过程中3种耕作方式的径流损失及磷素流失均以地表损失为主，径流中磷素以可溶性磷流失为主。

Effects of Tillage Practices on Soil Erosion and Phosphorus Loss in Sloping Cropland of Purple Soil

【Objective】The characteristics of soil erosion and phosphorus losses caused by rainfall on the scattered sloping cropland in purple soil during the maize maturity were studied in order to provide a theoretical evidence for the prediction, assessment and control of soil nutrient loss and coordinate land management to improve the ecological environment in purple soil area.【Method】The simulated rainfall experiments and runoff plot experiments were employed to investigate the characteristics of surface erosion, subsurface runoff and phosphorus loss among different tillage practices(flat planting, longitudinal ridge and cross ridge) during the maize maturity. Rainfall intensity is 1.7 mm•min-1, rainfall duration for 40 mins.【Result】Tillage practices had no significant influence on the phosphorus concentration in surface runoff，longitudinal ridge produced maximal amount of surface erosion and surface phosphorus loss. Meanwhile，it produced minimal subsurface runoff and subsurface phosphorus loss. Conversely, cross ridge produced minimal surface erosion and surface phosphorus loss，but the subsurface runoff was extremely serious. Although, the total of subsurface runoff were less compared with surface runoff under every tillage practice, but the phosphorus content was very high, the total phosphorus concentration all reached 0.2 mg•L-1, which were about 1.3 times higher than the surface runoff.【Conclusion】On the scattered sloping cropland, longitudinal ridges should not be adopted in normal agricultural production. Cross ridge was proven to be highly effective in control of both soil erosion and P losses, but attention needs to be paid to ridge repairing and protecting. In the whole process of erosion, the surface runoff was a large portion of the total runoff and phosphorus losses, and phosphorus loss in runoff was mainly in a form of dissolved phosphorus.