| Soil crust is the dense structure formed by soil in arid and semi-arid regions under the action of rainfall and runoff compaction.Contour tillage is one of the measures that people often use to reduce soil and water loss.Studies about the effects of contour tillage and soil crust on runoff and sediment yield are mainly carried out in the loess plateau region,but less in the loess area of hebei province.In addition,the effects of single factor on runoff and sediment yield were studied more and the effects of interaction of factors on runoff and sediment yield were studied less.Therefore,in this study,loess area in hebei province was as study area and indoor artificial rainfall simulation was used to evaluate the effects of contour tillage and soil crust on runoff and sediment yield.In this study,the effects of the interaction of rainfall intensity,slope,tillage measures,and soil crust on runoff and sediment yield were also studied.The main research conclusions were as follows:(1)Compared with the straight slope,contour tillage could delay slope runoff generation and reduce slope runoff yield.With the increase of slope and rainfall intensity,the ability of contour tillage to reduce slope runoff decreased gradually.Compared with the straight slope,contour tillage could reduce slope sediment yield,especially under the conditions of gentle slope and low rain intensity.(2)Soil crust could promote slope runoff compared to non-crusted soil.With the increase of slope and rainfall intensity,the effect of soil crust on promoting slope runoff decreased gradually.In the process of rainfall erosion,the soil crust to some extent retarded the slope sediment yield.In the early stage of erosion,soil crust first inhibited the slope sediment yield,but with rainfall time,the runoff increased,soil crust promoted the slope sediment yield.It was found that,with the increase of the slope,the difference value of total slope sediment yield between soil crust and non-crusted soil decreased gradually.The total slope sediment yield of soil crust was only 1.05 times larger than that of non-crusted soil at 20°and there was no significant difference between them.The total slope sediment yield of soil crust decreased 39.37%than that of non-crusted soil under 30mm/h.But the total slope sediment yield of soil crust increased 38.65%and 11.08%respectively than that of non-crusted soil under 60mm/h and 90mm/h.Ridge height influenced the effect of soil crust on slope sediment yield.When the ridge height was lower,soil crust would increase slope sediment yield;when the ridge height was higher,soil crust would reduce slope sediment yield.(3)Through correlation analysis,results showed that rainfall intensity and slope had significantly positive correlation relationship with slope runoff and sediment yield(P<0.01).While tillage measures had significantly negative correlation relationship with slope runoff and sediment yield(P<0.01).The correlation between soil crust and slope runoff and sediment yield were not significant.According to the analysis of multivariate anova,results showed that the single effect of rainfall intensity,slope,tillage measures and soil crust were significant on slope runoff and sediment yield(P<0.01).The double factors effects of rainfall intensity × slope were not significant on slope runoff and sediment yield.The three factors effects of rainfall intensity × slope × tillage measures,rainfall intensityxslope × soil crust were not significant on slope runoff and sediment yield.The four factors effects of intensity × slope ×tillage measuresx soil crust were significant on slope runoff and sediment yield(P<0.01). |
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