等高耕作对不同坡度坡面土壤侵蚀过程的影响

Effects of Contour Tillage on Soil Erosion Process in Different Slope

等高耕作是一种典型的农业耕作措施,通过影响坡面填洼、入渗等进而影响坡耕地坡面土壤侵蚀过程。通过人工模拟降雨试验,设计降雨强度(90 mm/h)、5个地表坡度(3°,5°,10°,15°,20°)以及2种坡面处理(等高耕作和平整坡面),对径流强度、侵蚀率、径流含沙量、减流减沙效益等指标进行综合对比分析,与平整坡面进行比较,探究了黄土高原坡耕地等高耕作措施对坡面土壤侵蚀过程的影响。结果表明:(1)与平整坡面相比,等高耕作明显延缓坡面初始产流时间,使初始产流时间延迟11.58~31.91 min,随着坡度增大,等高耕作初始产流时间延长效应逐渐减弱。(2)等高耕作具有削弱径流强度和侵蚀率的作用,与平整坡面相比,等高耕作的坡面径流强度、侵蚀率和径流含沙量分别减少11.77%~94.92%,20.69%~99.27%和2.46%~88.40%。但等高耕作减少产流产沙能力有限,若坡面发生断垄,等高耕作坡面的径流强度、侵蚀率、径流含沙量都可能接近或大于平整坡面。(3)在降雨过程中,累计产沙量与累计径流量之间满足线性正相关关系,等高耕作累计产沙量随累计径流量的增大幅度始终小于平整坡面。(4)等高耕作在不同坡度均具有较好的减流减沙效益,减流与减沙效益分别可以达到45.35%~100%与58.92%~100%,且减沙作用明显优于减流作用。研究结果揭示了等高耕作对坡面侵蚀过程的影响机制,为坡耕地土壤侵蚀治理提供科学依据。

Contour tillage is one of the typical agriculture tillage measures,which affects the soil erosion process of sloping farmland by affecting the slope filling and infiltration.In this study,the rainfall intensity(90 mm/h),five surface slopes(3°,5°,10°,15°,20°)and two types of slop treatments(contour tillage and flat slop)were designed through artificial simulated rainfall experiments,comprehensive comparison and analyses of indicators such as runoff rate,sediment rate,runoff sediment concentration and runoff reduction and sediment reduction benefits were carried out,compared with the flat slope,the effects the contour tillage on soil erosion process of slopeing farmland on the Loess Plateau were explored.The results showed that:(1)Compared with flat slope,the initial runoff producing time on the slope was significantly delayed by 11.58~31.91 min under contour tillage.With the increase of slope,the effect of prolonged the initial runoff producing time under contour tillage was gradually weakened.(2)The runoff rate and sediment rate were weakened under contour tillage.Compared with flat slope,the slope runoff rate,sediment rate and runoff sediment concentration under contour tillage were reduced by 11.77%~94.92%,20.69%~99.27%and 2.46%~88.40%,respectively.However,the ability of contour tillage to reduce runoff and sediment production is limited,and the runoff tate,sedimeat rate and runoff sediment concentration under contour tillage slope may be closed to or greater than that of the flat slope if ridge breaking occurs on the slope.(3)In the process of rainfall,the relationship between the accumulated sediment production and the accumulated runoff meet the linear positive correlation,and the increase of the accumulated sediment production with the accumulated runoff under contour tillage is always smaller than that of flat slope.(4)The contour tillage has good benefits of runoff and sediment reduction on different slopes,the benefits can reach 45.35%~100%and 58.92%~100%respectively,and the sediment reduction effect is obviously better than the runoff reduction effect.The results revealed the influence mechanism of contour tillage on slope erosion process,and provided a scientific basis for soil erosion control in slope farmland.