Influence Of Wind Erosion On Physicochemical Properties Of Farmland Soil In Bashang District

The wind erosion of farmland in the agro-pastoral ecotone of northern China is very serious,which causes loss of soil fertility and degradation of soil resources.Taking Kangbao County in Bashang district as a typical area,by model estimation,field sampling and laboratory test,this paper estimated the potential wind erosion loss of farmland under different farming methods.Then the loss characteristics of soil and the change characteristics of physicochemical properties in farmland soils led by wind erosion was studied in the paper.The main results are as follows:（1）Comparing with the wind erosion quantity of farmland estimated by the improved particle-size distribution comparison method,the WEEM model was built based on the natural environment of Bashang area was more suitable for estimating the wind erosion of farmland soil in Bashang area.Therefore,the WEEM model was chosen to estimate the average annual wind erosion of farmland in Kangbao County under tillage and stubble condition.The results showed that wind erosion quantity of farmland under plow tillage was from 12.18 to 69.77 t·hm^-2·a^-1,with an average of36.49 t·hm^-2·a^-1;that under stubble conditions was from 1.03 to 25.17 t·hm^-2·a^-1,with an average of 12.14 t·hm^-2·a^-1,which was only one third of that under plow tillage,thus surface residual coverage could alleviate the soil wind erosion.The wind erosion intensity showed decreasing tendency approximately from north to south due to the difference of rainfall and wind conditions between the south and the north region.（2）The physicochemical properties of aeolian sediment were greatly affected by properties of topsoil,showing that the contents of clay,silt,soil aggregates less than0.5 mm and nutrient in aeolian sediment presented the increasing trend with contents of corresponding material increased in situ soil.The contents of fine particle and nutrient of aeolian sediment were higher than that of situ soil,which indicate a large amount of fine particles and nutrients in the soil was lost during the wind erosion.Furthermore,it was found that the loss of clay,silt,organic matter and total nitrogen in soil under tillage conditions was 1.17 t·hm^-2·a^-1、7.64 t·hm^-2·a^-1、0.67t·hm^-2·a^-1、0.04 t·hm^-2·a^-1respectively,which were higher than those under stubble condition during wind erosion.Moreover,the loss intensity of fine particle and nutrient in farmland soil decreased from north to south both under tillage and stubble condition due to the difference of wind erosion intensity between the south and the north region.（3）Comparing with natural grasslands with weak wind erosion,the contents of clay and silt in farmlands decreased by about 30%and 14%,respectively,which leads to an increase in sand and the average particle-size.Also,the farmland soil has a various tendency of coarsening and desertification under the long-time effect of wind erosion.With the loss of fertile fine particles,the contents of carbon（C）and total nitrogen（N）in farmland soils decreased significantly,with a declining range of about29%and 24%,respectively.The ratio of C to N（C/N）also declined obviously and the shortage of carbon（C）element can become worse in the process of plant growth.In addition,the trend of the change of soil erodibility by wind was not obvious in farmland soils because of the influence of gravel and other factors.