秸秆覆盖红壤径流养分流失效益及径流剪切力影响研究

采用模拟降雨试验的方法,研究秸秆覆盖条件下红壤侵蚀效益及动力影响因素。模拟降雨强度2.0mm/min,坡度20°,径流小区(长1.5m,宽0.5m,深0.3m)条件下,供试土壤为赤红壤。结果表明:(1)秸秆覆盖减流效益达到69.3%,减沙效益达到99.2%;明显提高土壤的入渗速率,渗透效益达到了32%,秸秆覆盖有较好的水土保持效益。(2)秸秆覆盖有效减少径流总氮、径流溶解态氮、径流颗粒态氮、径流总磷、径流溶解态磷、径流颗粒态磷的流失,减少径流中氮流失效益均达到74%以上,减少径流中磷流失效益均达到78%以上,径流中元素流失均以溶解态氮磷元素大于颗粒态氮磷元素,秸秆覆盖减少径流中磷养分流失的效益大于氮养分的流失效益。(3)建立单位面积单位时间径流剪切力和产沙率、径流总氮、径流溶解态氮、径流颗粒态氮和径流总磷、径流溶解态磷、径流颗粒态磷流失速率的模型,初步推断径流剪切力是土壤侵蚀的主要动力因素。(4)秸秆覆盖和未覆盖的临界启动径流剪切力分别为2.8N/m2和1.5N/m2。

Effects of Straw Mulching on Soil Erosion Benefits and Runoff Shear Force Under Simulated Rainfall

By the experiments of simulated rainfall, the effects of straw mulching on nitrogen and phosphorus loss and runoff shear force were studied. Soil plots (1.5 m length × 0.5 m width × 0.3 m height) and rainfall intensity (2.0 mm/min) and slope gradient (20°) were established. Latosolic red soil was selected. The results showed that: (1) Straw mulching significantly decreased sediment yield and runoff volume, the benefit was 69.3% in sediment yield, and 99.2% in runoff volume. The infiltration rate of soil was improved at 32%, so straw mulching could conserve soil and water significantly. (2) Straw mulching significantly decreased the loss of runoff-associated total nitrogen, particulate nitrogen, dissolved nitrogen and total phosphorus, dissolved phosphorus, particulate phosphorus, and the loss benefits were more than 74% in nitrogen more than78% in phosphorus. The runoff-associated dissolved nitrogen and phosphorus loss were greater than the particulate nitrogen and phosphorus loss. Straw mulching reduced the runoff-associated phosphorus loss greater than that of nitrogen. (3) Cubic equations were established between runoff shear force per unit area per unit time and runoff-associated nitrogen and phosphorus loss rates and sediment yield rates, and the preliminary inference indicated that runoff shear force was the main dynamic factor of soil erosion. (4) The critical starting runoff shear force was 2.8 N m-2 under straw mulching, and 1.5 N m-2 under non-straw mulching.