Effects Of Different Straw Mulching Modes On Water And Salt Transport In Sandy Loam Soil

Evaporation of soil water mainly occurs via soil capillary.Water supply capacity of soil capillary determines intensity of soil evaporation.Severe soil evaporation leads to congregation of salt on soil surface,and then causes the problem of soil salinization in the arid earth of Northwest China.Explore a reasonable scheme to block the capillary channel on the surface of the soil,could potentially set effective partitions on the surface and below the surface of the soil,improve the soil moisture conservation capacity,and cut off the water supply capacity of the soil capillary.This can reduce soil water evaporation and effectively slow down the occurrence of soil salinization.From this view,this study adopts sand+straw and double-layer straw mulching mode,through indoor and outdoor simulation experiments and HYDRUS-1D model research,compares the water and salt transport law of sandy loam under different straw mulching modes,in order to provide theoretical support for soil salinization control and agricultural soil improvement in arid areas of Northwest China.Main contents and conclusions are as follows:(1)Through outdoor evaporation bucket simulation experiment,the inhibitory effect of sand and gravel+straw mulching on soil water evaporatio n was studied.Results showed that,compared with bare soil,the soil covered with sand and gravel+straw had the effect of moisture conservation and steam inhibition;soil water evaporation varies with the thickness of straw mulch.The greater the mulch thickness,the less the soil water evaporation.The cumulative evaporation of bare soil measured in the experiment is 1213.97g.Compared with bare soil,the evaporation of different mulches is reduced by 86.07%,91.77%and 94.50%respectively.(2)Through indoor soil column evaporation simulation experiment,the variation law of soil water evaporation under double-layer straw embedding was studied.Results showed that the evaporation process could be divided into three stages.Under the control of five group s covered with 80mm single layer straw(CK),0mm+300mm double layer straw(C1),80mm+220mm double layer straw(C2),80mm+300mm double layer straw(C3)and 80mm+380mm double layer straw(C4),the total evaporation of CK was 3154.20g for 1～10d,CK>C4>C2>C1>C3,11～18D,CK>C1>C4>C3,19～24D,C2>C1>CK>C4>C3,compared with CK The steam inhibition rates of C1,C2,C3 and C4 treatments were 2.04%,3.98%,8.63%and 2.66%respectively.The cumulative evaporation of C3 treatment was lower than the rest of controls other controls,Which indicates that 80mm+300mm double-layer straw mulching was a better way to inhibit soil water evaporation.(3)Through indoor soil column evaporation simulation experiment,the variation law of soil water evaporation under double-layer straw embedding was studied.Results showed that,different bury depth of double-layer straw was correlated with soil water evaporation,and the evaporation was not positively correlated with the buried depth of lower stra w.The fitting of soil water equation Y(28)a·x~b under different straw burial depth is the best,which is more in line with relationship between soil water cumulative evaporation and time.(4)Dynamic changes of soil moisture content and soil profile water distribution during wheat growth under double-layer straw mulching was also investigated through HYDRUS-1D model.Results showed that the variation trend of soil water content under different treatments was same during the study period.After irrigation,water distribution in each profile was positively correlated with the soil depth.The average soil water content of 0～20cm of topsoil is 0.161cm~3/cm~3,the water content of 20～40cm increases by 0.051 cm~3/cm~3 compared with the first layer,the water content of 40～60cm increases by 0.082 cm~3/cm~3 compared with the first layer,and the water content of 60～80cm increases by 0.065 cm~3/cm~3 compared with the first layer.(5)Dynamic changes of soil salt content and soil profile salt distribution under double-layer straw mulching were studied by HYDRUS-1D model.Results showed that each treatment could effectively inhibit the rise of salt in 40-80 cm layer,but the compound increase of salt in 0～20cm layer was obvious.The slope of the variation curve of 0～20cm interlayer conductivity versus time is the largest,and salt increase is in the accelerated stage 10-20 days after irrigation.According to the data calculation,salt content of 20cm soil layer under C3 treatment is the lowest,and the average conductivity is reduced by 4.57%,9.75%and 7.42%compared with the other three groups.Above all,this shows that burying double-layer straw at 80mm and300mm of soil layer behaves much better on the salt control of soil 0-20cm layer.