Effects Of Ridge Tillage And Straw Returning On Soil Erosion At Sloping Croplands In The Black Soil Region

Soil erosion is a persistent natural hazard faced by today’s society.Unreasonable production activities accelerate the harm of soil erosion.As an important commodity grain production area in China,soil erosion in the black soil region of Northeast China has seriously restricted the agricultural production and economic development.Ridge tillage has many advantages and is a very common tillage method in the Chinese black soil region.Straw returning is an important way to effectively control soil erosion at sloping croplands,which is also an important soil and water conservation measure promoted widely in the black soil region of China.However,there are still deficiencies in the research on the effects of different ridge tillage and straw returning methods on soil erosion prevention and control based on field in situ croplands.Thereinto,the lack of quantitative analysis of runoff process and soil erosion process is especially obvious.In view of this,this paper studied the runoff process,runoff amount,runoff reduction effect,soil erosion process,soil erosion amount,and soil erosion reduction effect of different ridge tillage and straw returning patterns based on natural runoff plots located in situ sloping cropland by using the simulated rainfall method.The main conclusions are as follows:(1)The runoff rates and soil loss rates for different ridge tillage treatments gradually increased with an increase in the rainfall under the experimental conditions.Once ridge failure occurred,the peak values of runoff rates and soil loss rates increased as the rainfall intensity increased,and the traditional contour ridge tillage showed a more significant increase than those of the other treatments.The traditional contour ridge tillage effectively regulated the runoff and soil erosion processes at gentle croplands,but had ridge failure occurred at steep croplands.After the collapse of the ridge,the peak values of runoff rate and soil loss rate increased by 101.8%～192.9% and 63.3%～91.3% respectively compared with those before ridge failure for the traditional contour ridge tillage treatment.Additionally,the peak values of runoff rate and soil loss rate increased by 48.2%～776.5% and 79.0%～965.1% respectively compared with those before ridge failure for upslope longitudinal ridge + downslope contour ridge tillage treatment.Therefore,different ridge tillage patterns could significantly affect the runoff and soil erosion processes at sloping croplands.(2)Compared with the traditional longitudinal ridge tillage treatment,the total runoff amounts of ridge-furrow intervals tillage treatment,upslope longitudinal ridge + downslope contour ridge tillage treatment,contour ridge + drainage ditch tillage treatment decreased by45.5%,48.2%,44.2%;the total soil erosion amounts of them decreased by 85.2%,83.8%,88.0%,respectively.Furthermore,the traditional contour ridge tillage treatment could effectively decrease both runoff and soil erosion amount at sloping croplands before ridge failure.For the 5° slope gradient,the runoff reduction effects of traditional contour ridge tillage treatment,ridge-furrow intervals tillage treatment,upslope longitudinal ridge + downslope contour ridge tillage treatment were 83.9%,41.3%,40.8%;the soil loss reduction effects of them were 94.6%,79.8%,79.2%,respectively.For the 10° slope gradient,the runoff reduction effects of traditional contour ridge tillage treatment,contour ridge + drainage ditch tillage treatment were 38.1%,40.6%;the soil loss reduction effects of them were 65.2%,87.0%,respectively.Thus,the traditional contour ridge tillage pattern could effectively regulate runoff and control soil erosion at relatively gentle croplands,but it was better to add drainage ditch or some other drainage measures into the traditional contour ridge tillage at steep croplands to improve the runoff and soil loss reduction effects in the black soil region.(3)The runoff rates of different straw returning patterns increased with an increase in the rainfall,and the difference among the straw returning patterns became more obvious as the rainfall intensity increased.Compared with the longitudinal ridge tillage treatment without and straw returning,straw returning treatments delayed runoff yield time 14.0 min and 4.8 min under 50 mm/h and 100 mm/h rainfall intensity,respectively.The soil loss rates of straw returning treatment was significantly lower than that of the longitudinal ridge tillage treatment without and straw returning.The soil loss rates of straw returning treatment showed a relatively stable changing trend with rainfall.Therefore,the straw returning measures could effectively regulate runoff processes and control soil erosion processes.(4)Different straw returning patterns effectively decreased total runoff and soil erosion amounts at sloping croplands under the experimental conditions.The control effect of straw returning on total soil erosion amount was greater than that on total runoff amount.The runoff reduction effects of straw returning treatments were 37.0%～66.6% and 36.6%～64.9%;the soil loss reduction effects of straw returning treatments were 87.2%～96.8% and 82.6%～96.8%,respectively.Among them,the no-tillage with straw mulching had the best effect on reducing runoff and soil erosion,followed by the patterns of smashed straw turnover and deep application of straw.Therefore,the pattern of no-tillage with straw mulching was a suitable straw returning method for sloping croplands in the black soil region of Northeast China.