Study On Infiltration Mechanism Of Ridge Tillage On Gravel-Mulched Fields In Arid Region Of Northwest China

Rainfall resources have an important influence on soil moisture content and the development of dry farming in the arid regions of Northwest China.The gravel-mulched field has the effect of increasing precipitation infiltration and reducing surface runoff and soil moisture evaporation.The ridge-furrow rain harvesting technology can collect water flow,automatically regulate the soil moisture content between ridges and furrows,and improve the soil storage of precipitation resources.The tillage technology combined with gravel-mulched field and ridge-furrow rainwater harvesting can improve the soil conservation effect on precipitation resources and reduce the adverse effects of gravel-mulched field degradation.In view of this,this paper takes the tillage mode of the combination of gravel-mulched field and ridge-furrow rainwater harvesting technology in the northwest arid area of China as the research object,through the combination of simulation rainfall test and HYDRUS-2D numerical simulation,the influence of different precipitation intensity,soil-gravel mixing ratio and ridge way on the rainfall infiltration and migration of slope soil in gravel-mulched field is studied,and the reliability of the numerical model is verified by the experimental results.On this basis,the effects of different soil-gravel mixing ratios and ridge modes on soil moisture migration during maize growth period are simulated.The main research contents are as follows:(1)In order to investigate the effects of different precipitation intensities and ridge tillage methods on rainfall infiltration on gravel-mulched field slope,simulated rainfall experiments were conducted to study the effects of 15,54 and 93 mm/h rainfall intensities and single ridge,double ridge and flat ridge tillage methods on rainfall infiltration and migration on gravel-mulched field slope.The results showed that the cumulative infiltration of single ridge,double ridge and flat ridge in the lower part of the soil groove slope was greater than that in the upper part of the slope,and the cumulative infiltration of the upper and lower parts of the flat soil groove slope was greatly affected by rainfall intensity.The initial infiltration rate of soil water increased with the increase of rainfall intensity,and the infiltration rate of soil water in double ridge was higher than that in single ridge and flat tillage.The moisture content of the wet soil profile under the soil groove slope under the three different ridge tillage methods was higher than that on the soil groove slope.It is concluded that the Kostiakov infiltration model is suitable for the rainfall infiltration of soil on the slope of sandy land under different rainfall intensities,and the correlation coefficient R~2 is between 0.8164～0.9917.(2)In order to reveal the effects of different soil-gravel mixing ratios and ridge tillage methods on soil rainfall infiltration on the slope of gravel-mulched field,the effects of five different soil-gravel mixing ratios(10%,30%,50%,70%,100%(CK)and single ridge,double ridge and flat ridge tillage methods on rainfall infiltration and migration on gravel-mulched field slope were studied by simulated rainfall infiltration experiments.The results showed that the cumulative infiltration of single ridge,double ridge and flat ridge in the lower part of the soil groove slope was greater than that in the upper part,and the cumulative infiltration of the upper and lower parts of the flat soil groove slope was significantly related to the soil-gravel mixing ratio.With the increase of soil-gravel mixing ratio in coating layer,the cumulative infiltration decreased.Under the same soil-gravel mixture ratio covering condition,the soil moisture of gravel-mulched field with double ridges was slightly larger than that of single ridge,which proved that the rainwater harvesting effect of double ridges was better than that of single ridge to some extent.It is concluded that the Kostiakov infiltration model is suitable for the rainfall infiltration on the slope of gravel-mulched field under different soil-gravel mixing ratios,and the correlation coefficient R~2 is between 0.9352～0.9917.(3)Based on HYDRUS-2D,the numerical model of rainfall infiltration and migration of ridge-furrow soil on gravel-mulched field slope was established.The infiltration and migration of soil moisture on gravel-mulched field slope under different rainfall intensity,soil-gravel mixing ratio and ridging mode were simulated and analyzed.The reliability of the model was verified by experimental results.The coefficient of determination R~2 between simulated and measured cumulative infiltration is between 0.8009～0.9974,and the coefficient of determination R~2 between simulated and measured soil water content is between 0.7507～0.9968,indicating that the simulated values of cumulative infiltration and soil water content are close to the measured values,and the model is basically reliable.(4)Taking maize as the research object,based on HYDRUS-2D,the numerical models of natural precipitation infiltration and migration in maize growth period under different soil-gravel mixing ratios and ridge planting modes were established.The soil moisture migration law on the slope surface of gravel-mulched field under 10 treatments of 10%,30%,50%,70%and 100%five soil-gravel mixing ratios and single ridge and double ridge two ridge planting modes were simulated and studied.The results showed that the soil-gravel mixing ratio and ridging mode had significant indigenous effects on soil moisture content during maize growth period.Under the condition of the same soil-gravel mixing ratio,the soil moisture content of double ridge is greater than that of single ridge.With the increase of soil-gravel mixing ratio,the soil moisture content decreased,and were greater than the soil moisture content of CK.It can be shown that gravel-mulched field and ridge tillage play an important role in improving the utilization rate of precipitation resources and developing dry farming.