Soil Desiccation Characteristics And Influence Factor On The Gravel-sand Nuilched Field In The Arid Zone Of Central Ningxia, China

The gravel-sand mulched field is a kind of dryland conservation tillage method created by farmers relying on natural precipitation in order to resist harsh natural environments,using the mixture of gravel and coarse sand as the cover material.It has a significant role in improving soil environment,inhibiting water evaporation,increasing infiltration and so on.However,with the continuous improvement of soil water consumption of crops and forest grass and the unreasonable utilization of land,soil desiccation has been paid more and more attention.The production of soil desiccation will lead to the aggravation of crop yield fluctuations and the decline of the forest and grass,and will also obstruct the vertical infiltration of soil moisture and influence the process of land water circulation.Therefore,taking gravel-sand mulched field as the research object in the arid zone of central Ningxia.through the field observation of the basic physical properties and water content,four quantitative indexes(SDI,Soil dryness index;DSLT,Thickness of dried soil layer;DSL-SWC,Soil water content in the inner of dried soil layer;DSLFD,Forming depth of dried soil layer)are selected,with the help of classical statistics and geostatistics,GS+9.0,ArcGIS10.1,GWR4.0 and other software were used to study the spatial distribution characteristics and driving mechanism of soil desiccation,in order to support the continuous utilization of soil in the gravel-sand mulched field in the arid zone of central Ningxia.The results showed that:(1)There is a certain soil desiccation phenomenon under different grow plants in the g ravel-sand mulched field,and the soil water storage and available water storage are lower than the stable field capacity and water storage in the local field.The degree of soil desiccation from strong to weak is Caragana land>Oleaster land>Chinese wolfberry land>abandoned cropland>watermelon land.The environmental factors such as grow plants and clay content,saturated hydraulic conductivity,field capacity are important factors affecting the soil dryness index and soil water content in the inner of dried soil layer.(2)Soil water storage and available storage under different planted years in the gravel-sand mulched field are slightly higher than the stable field capacity and water storage in the field,but the water content of the soil which is planted at 16 a and 25 a is lower than the stable field capacity.With the increase of planting years,the drying strength and dry layer thickness are gradually increasing.The environmental factors such as planting years and field capacity are important factors affecting the thickness of dried soil layer and soil water content in the inner of dried soil layer.(3)There are obvious spatial variation characteristics and distribution patterns of soil physical properties on the gravel-sand mulched field in the study area,which is caused by the common effects of various factors and human activities within and outside the region.The classical statistics indicated that the soil bulk density is weakly variable,saturated hydraulic conductivity is strong variation,and other soil properties show moderate variability.The geological statistics indicated that the spatial variability of soil saturated hydraulic conductivity is mainly influenced by random factors,and the other soil properties is mainly influenced by structural factors.In spatial distribution,the content of clay silt,field capacity and permanent wilting permanent wilting point decreased gradually from the southeast to the north and West,and the content of sand was the opposite.The bulk density decreased gradually from central and south to four sides,the total porosity,the capillary porosity and the saturated water content were the opposite.The saturated water conductivity showed high heterogeneity,and the greater porphyritic in the South and northwest,and thus decreasing to around.(4)The phenomenon of soil desiccation is widespread on the gravel-sand mulched field in the study area,and there is obvious spatial variation characteristics and distribution patterns.The soil moisture content is decreasing in 60?600 cm and then increasing slowly.The quantitative indexes of soil desiccation are all medium spatial dependence,which are both the result of the combination of randomness and structural factors.The degree of soil desiccation decreased gradually from south and northeast corner to four sides,and there was a larger porphyry in some areas.There was a significant correlation between all quantitative indexes of soil dryness.(5)Soil bulk density,grow plants,planting years and clay content are the main factors affecting the degree of soil dryness.By comparing the GWR model and OLS model,the GWR model can not only improve the prediction accuracy and determining coefficient of the regression equation,but also reduce the residual difference,and can also pass the local parameter estimation to the spatial expression of the quantitative indexes of soil desiccation,the results more intuitive than OLS model.