保护性耕作对坡耕地土壤水分特性和水土流失的影响

在黄土高原西部丘陵沟壑区水土流失严重的坡耕地进行了2 a的定位试验,研究了不同耕作方式对坡耕地土壤水分特性和水土流失的影响.研究结果表明:(1)免耕+覆盖的保护性耕作方式保水效果明显,全年平均土壤含水量比传统耕作高出1%以上,单纯的免耕与传统耕作没有显著差异.(2)免耕可使耕作层土壤水分保持相对稳定,初春播种后土壤较长时间保持较高含水量有利于作物出苗;雨后免耕处理耕作层具有更强保水能力,从而使土壤水分保持相对稳定则有利于作物生长.(3)不同耕作方式对坡耕地土壤水分特性的影响与其对士壤结构的影响有关,免耕虽然增加了耕作层土壤容重,但也增加了团聚体的稳定性,降低了团聚体破坏率,增强了土壤抗蚀力,覆盖能降低免耕地表层土壤容重,增强其持水与保墒能力.(4)免耕措施未必能减少坡地径流量,但可显著降低土壤侵蚀量,免耕辅以秸杆覆盖的保护性耕作可有效防止水土流失,径流量和产沙量较传统耕作处理分别减少了8.35%和88.11%.

Effects of Conservation Tillage on Soil Water Characteristics and Soil Erosion in Slope Farmland

After two years' experiment in the west loess hilly and gully region with serious soil erosion,the effects of various tillage ways on soil water characteristics and soil erosion in slope farmland were studied. Results showed that (1) No-tillage with straw covering had good water conservation effect and its mean soil water content in a year was 1% higher than traditional tillage. There was no obvious difference between the no-tillage and traditional tillage. (2) Soil water content in cultivated layer kept steadily in the no-tillage,which benefits seedling emergence in early spring and crop growth after rainfall. (3) The effects of various tillage ways on soil water characteristics were related to the change of soil structure. Soil bulk density was increased by the no-tillage,the destruction ratio of soil aggregates was reduced,and the anti-erosion ability of soil was increased by the increment of the stability. Straw covering reduced soil bulk density and enhanced soil water retaining capacity. (4) The no-tillage might not reduce runoff on farmland,but it obviously controlled soil erosion. No-tillage with straw covering controlled soil and water loss efficiently and runoff and soil erosion were reduced by 8.35% and 88.11%,respectively.