Study On Runoff And Sediment Yield And Soil Water Distribution Of Different Tillage Patterns In Northern Slope Farmland

In the north of China,the sloping land is widely distributed,the rainfall months are concentrated and the rainfall is large.In addition,human disturbance and unscientific farming methods have a comprehensive impact on the soil structure of the sloping land,resulting in different degrees of damage.It leads to the frequent occurrence of soil and water loss on the slope and the disorder of soil water distribution pattern,which is extremely unfavorable to the growth of crops and the prevention and control of soil and water loss on the slope land.Therefore,it is of great significance for the protection and effective utilization of soil and water resources to study the effect of soil and water conservation and the spatial distribution of soil water on different cultivation patterns,the research object of this paper is soybean field with 10° slope in North China,under natural rainfall conditions,the amount of abortion sand and soil water content of 0 ~ 100 cm in the inner slope of soybean were monitored in the four kinds of treatment of slope surface: conventional tillage,zero tillage,no tillage straw cover and contour ridging,the effect of water and sand reduction on slope surface of different farming modes and the mechanical composition characteristics of soil particles were analyzed,the temporal stability and spatial distribution of soil moisture on different tillage patterns were summarized,the optimal tillage model suitable for cultivated land on the northern slope is defined.The main conclusions of this paper are as follows:(1)The runoff and sediment yield of different tillage patterns were CT > CR > ZT > NT;The influencing factors of runoff are as follows: rainfall > vegetation coverage > wind speed > 25 cm deep soil temperature.and the influence degree of the sediment yield is runoff > rainfall > vegetation coverage > wind speed;The protective effects of different tillage patterns on different soil particles are different,among which NT,ZT,CT and CT are the best for coarse sand,fine sand,silt and clay,and CT,CT,CT,ZT and NT are the worst.(2)The relationship between the fractal dimension of soil particles lost by different tillage patterns is nt > ZT > CR > CT,which indirectly shows the protection effect of different tillage patterns on the stability of slope soil structure;The fractal dimension of lost sediment particles is directly proportional to the content of silt and clay particles,and inversely proportional to the content of coarse sand and fine sand particles,and the content of clay and coarse sand particles has a greater impact on it;The mechanical characteristics of the particles are analyzed by the theory of moment method,the coefficient of unevenness and the coefficient of curvature of the grading curve.(3)The depth of 0-40 cm in the vertical direction of the soil moisture content of the slopein the different cultivation patterns experimental plot is nt > ZT > CR > CT.When the soil depth is more than 40 cm,the relationship between the soil moisture content and the soil moisture content begins to fluctuate,in the horizontal direction,the relationship between the soil moisture content of CT and ZT treatment slope is less affected by the total rainfall during the soybean growth period,which is shown as: downhill > middle slope > uphill and downhill? middle slope > uphill,while the soil moisture content of NT and Cr treatment slope changes slightly with the total rainfall during the soybean growth period.(4)The spatial distribution pattern of soil moisture in different cultivation patterns showed the characteristics of lower wet and upper dry,but the spatial distribution range and location of relative wet and dry soil areas were different,among the three factors considered,the effect on soil moisture content is: cultivation mode > profile depth > slope position;Compared with CT treatment,Cr,ZT and NT significantly increased soybean yield and water use efficiency,with an average increase of 8.77%,15.68% and 26.74% in yield and 6.32%,11.6% and 20.61% in water use efficiency;It is concluded that "no tillage straw mulching" is the optimal farming mode.(5)With the minimum SDRD value as the evaluation index,the differences of soil moisture time stability in different cultivation modes are as follows: NT ? ZT > Cr ? CT;For sloping farmland,the accurate effect of different evaluation indexes of soil moisture time stability is as follows: The correction value of the SDRD minimum value measurement point > SDRD minimum value measurement point = ITS minimum value measurement point > MABE minimum value measurement point > MED closest to 0;Based on Spearman's rank correlation coefficient,the temporal stability of soil moisture in each plot showed NT >ZT > CT > CR.(6)When CT and NT treatment were in the range of 0-100 cm,the stability of soil was better in time;In ZT and CR treatment,when the depth of the soil profile is greater than80 cm and 90 cm,the relative position of the extreme dry and wet state of the soil will change;In the depth range of 0-100 cm,except for ZT,the representative points of soil moisture content in different depth soil layers of other cultivation modes are all located in the middle of the slope,while ZT tends to the middle and lower part of the slope.The estimation effect of the average value of soil moisture in each plot will become more accurate with the deepening of the profile depth;In different depth range,the stability of soil moisture was different among different treatments,and the similarity of spatial distribution pattern of soil moisture was NT > ZT > CT > CR.(7)The coefficient of variation of soil water content in different depth ranges is between6% and 19% in the whole experimental area,in which the upper layer(0-50cm)soil waterbelongs to medium strength variation,while the lower layer(50-100cm)soil water belongs to weak strength variation;Compared with random factors,structural factors have more influence on spatial variation of soil water content;The range of spatial autocorrelation distance of soil water content is 12.748-66.300 m,the average of the range of the lower soil is larger than that of the upper soil,and the semi variance fitting model of soil water content is mainly Gaussian model.