三峡库区坡耕地免耕秸秆覆盖下氮磷流失特征

为有效防治三峡库区坡耕地氮磷流失，在三峡库区长坪小流域连续进行两年野外径流小区监测试验。在自然降雨条件下进行免耕秸秆覆盖(SM)和对照(CK)两个处理的田间试验，研究了免耕秸秆覆盖措施对地表径流和氮磷养分流失的影响。结果表明：(1)降雨量与径流量极显著正相关，径流主要由几次暴雨事件造成，需要重点防范玉米季暴雨造成的水土流失。免耕秸秆覆盖能减少地表产流产沙，相比对照处理，免耕秸秆覆盖减少19.1%的径流流失，减少63.6%的泥沙流失。(2)免耕秸秆覆盖分别降低了21.3%,25.8%的总氮和总磷流失量，径流量和氮磷流失量呈极显著正相关，免耕秸秆覆盖主要通过减少径流量来减少氮磷流失。(3)坡耕地油菜—玉米种植制的氮磷流失风险期为6—7月初，该时期CK处理41.3%的径流量贡献了81.4%,52.1%的总氮和总磷流失，SM处理38.4%的径流量贡献了75.2%,48.2%的总氮和总磷流失，在该时期通过免耕秸秆覆盖可分别减少17.5%,31.7%的总氮和总磷流失。研究表明，免耕秸秆覆盖是控制三峡库区坡耕地氮磷养分流失的良好水土保持措施。

Characteristics of Nitrogen and Phosphorus Losses on Sloping Farmland Under No-tillage and Straw Mulch in the Three Gorges Reservoir Area

In order to effectively control the losses of nitrogen and phosphorus from sloping farmland in the Three Gorges reservoir area, the field runoff monitoring experiment was carried out in Changping Watershed for two consecutive years. A field experiment was conducted to study the effects of no-tillage straw mulching(SM)and control(CK)on surface runoff and nitrogen and phosphorus losses under natural rainfall conditions. The results show that:(1)there is a very significant positive correlation between rainfall and runoff; runoff is mainly caused by several heavy rain events; it is necessary to focus on preventing soil erosion caused by heavy rain in the corn season; no-tillage straw mulching can reduce surface runoff and sediment production; compared with the control treatment, no-tillage straw mulching reduces runoff loss by 19.1% and sediment loss by 63.6%;(2)no-tillage straw mulching reduced total nitrogen and total phosphorus losses by 21.3% and 25.8%, respectively; there is a very significant positive correlation between runoff and nitrogen and phosphorus losses; no-tillage straw mulching mainly reduces nitrogen and phosphorus losses by reducing runoff;(3)the risk period of nitrogen and phosphorus loss is from June to early July, during which 41.3% of runoff of CK contributes 81.4% and 52.1% of total nitrogen and total phosphorus losses, 38.4% of runoff of SM contributes 75.2% and 48.2% of total nitrogen and total phosphorus losses; in this period, total nitrogen and total phosphorus losses can be reduced by 17.5% and 31.7%, respectively, through no-tillage straw mulching. No-tillage straw mulching is a good soil and water conservation measure to control the losses of nitrogen and phosphorus nutrients from sloping farmland in the Three Gorges Reservoir area.