Effects Of Different Straw Application Methods And Bulk Density On Water Content Characteristics Of Black Soil

The soil structure in the black soil area of Northeast China has been destroyed due to improper land use,and the sticky texture of the blac k soil,resulting in weakened infiltration capacity and decreasing soil water holding capacity year by year.Therefore,it is important to apply straw resources to the soil to improve soil water characteristics and infiltration characteristics and improve water use efficiency.In order to reveal the effect of straw application on soil moisture characteristics and infiltration characteristics,this paper set different bulk density of 、 and,by measuring the soil moisture characteristics curve under different straw application ratios,and analyzing the pore changes and soil shrinkage characteristics in the process of soil dehydration,to study the effects of mixed straw application on soil moisture characteristics.Through the indoor one-dimensional vertical infiltration test,investigated the effects of straw layer application and mixed application on soil water infiltration and water redistribution characteristics at different soil depths,and analyzed the effects mechanisms of straw application method,application depth and soil capacity on soil water transport to provide reference and theoretical basis for the improve of soil structure and soil water-holding properties in the study area by straw application.The main research results are as follows:(1)Under the same soil water suction,soil water content decreases with the increase of soil capacity,and mixing straw can increase the soil water content,and the higher the application ratio the more obvious the increase effect;Van Genuchten model and Gardner model can well describe the soil water characteristic curve after straw mixed application.The soil water supply capacity increased with the increase of the capacity at the same straw application rate,and the soil water supply capacity was the strongest at 3%,3% and 1% of the soil capacity at 1.2 、 1.3and 1.4,respectively.(2)The total porosity of soil decreases with the increase of soil capacity under the same straw mixing ratio,and the larger the soil capacity,the smaller the proportion of large and medium porosity in the soil.Straw mixing affects the distribution of soil pore space,and there are differences in the distribution of soil pore space size by mixing straw at different bulk weights: the soil bulk density of 1.2,increase the soil total porosity,mix proportion was 1% increases the most obvious effect,while effectively increasing the proportion of large and small pore spaces and decreasing the proportion of medium pore spaces.When the soil bulk density is 1.3 and1.4,the total soil porosity and the proportion of macropores will be reduced,with the greatest reductions occurring at 3% and 1% mixes respectively,and also increased the proportion of medium and small pores.(3)The soil shrinkage was inhibited by mixing straw,and the soil shri nkage will increase logarithmically with the increase of soil water suction.Under the same straw ratio,the soil shrinkage degree decreased with the increase of soil bulk density.The soil shrinkage was inhibited by mixing straw at the same soil capacity,with the strongest inhibition of soil shrinkage at 3%mixing rate at 1.2 and 1.3,and the best inhibition of soil shrinkage at 1% mixing straw at 1.4.(4)The cumulative infiltration volume decreases with increasing soil capacity f or the same infiltration time.Priority flow occurred in the process of straw layer application,but no preferential flow occurred in the process of straw mixed application.Power function can well reflect the variation of soil moisture front under differe nt straw application methods.All straw application methods slow down the transport of wetting fronts and reduce the cumulative infiltration volume and infiltration rate,resulting in a reduction in soil water infiltration,with the cumulative infiltration volume decreasing with increasing straw application depth.The straw layer application process resulted in preferential flow,whereas no preferential flow occurred in the straw mix application.The Philip model,the Kostiakov model and the Horton model al l fitted the soil infiltration process after straw application well,with coefficients of determination greater than 0.90,0.93 and 0.95 respectively,with the Horton model fitting more accurately.(5)At the same soil depth,the water content of the soil profile decreases with increasing soil capacity.The results showed that straw layer application had effect on soil water movement after entering the straw layer,but had no significant effect on soil water redistribution above the straw layer.The difference in water content between 24 h and 48 h of mixed application of straw water redistribution is relatively small,which could promote the process of water redistribution.