A Comparative Study Of Three Typical Soil Properties And Infiltration Characteristics In The Water-wind Erosion Region Of The Loess Plateau

Soil erosion is serious in the water-wind erosion region of the Loess Plateau.The comparative study on the basic properties and infiltration capacity of the main soil types in this area are the basic work for controlling water and soil loss.In order to clarify the differences in properties of three typical soils widely distributed in the area,and provide a theoretica basis for different soils to carry out differentiated treatment.In this paper,the basic properties,root system,aggregate and infiltration characteristics of loess,aeolian sand and feldspathic sandstone in cropland and grassland were analyzed,and the ratio of compounding and improvement of the three soils were investigated.Results showed that:(1)The physical properties and root characteristics of the three soils at 0-30 cm were significantly different.On the whole,the loess was better than the aeolian sand,and the feldspathic sandstone was worse.Specifically,water-stable aggregates,organic matter,root length density,mean root diameter,root surface area density,saturated water content and total porosity showed as loess > aeolian sand > feldspathic sandstone.Loess has the most silt content,aeolian sand has the most sand content,and feldspathic sandstone has the most clay content.The physical properties and root system characteristics in grassland of aeolian sand and feldspathic sandstone were better than that of cropland,and which in grassland of loess were better than corpland in the 0-10 cm soil layer,and the lower layer were opposite.(2)The composition of large soil aggregates was aeolian sand > loess > feldspathic sandstone,and that in the surface layer of loess was better than corpland,the lower layer was the opposite,in aeolian sand was slightly better than corpland,and in feldspathic sandstone was opposite with aeolian sand.As the aggregate patical size increases,the proportion of large aggregates in loess was gradually higher than that in feldspathic sandstone,and the demarcation point was 2 mm particle size.Aggregates stability of aeolian sand was worst due to high structural damage rate and irregular shape.Feldspathic sandstone has good mechanical stability but poor water stability.Loess has the best water stability and more regular shape.The aggregate characteristics of loess were better than those of aeolian sand and feldspathic sandstone.Soil aggregate stability could be enhanced by increasing the content of soil organic matter,silt and clay.(3)The infiltration rates measured by Disc permeameter showed that feldspathic sandstone > aeolian sand > loess,and that of grassland was better than cropland.The saturated hydraulic conductivity measured in laboratory showed that loess > aeolian sand >feldspathic sandstone.The opposite experimental results reflect the small size and poor water stability of aggregates in feldspathic sandstone,higher particle size of microaggregates in aeolian sand,and larger particle size of aggregates in loess.Loess maintained good pore structure while the porosity in feldspathic sandstone and aeolian sand collapsed and lost during soaking.The number and porosity of macropores were consistent with disc infiltration performance,where pores > 0.5 mm accounted for 41～75% of the infiltration contribution.The difference in saturated hydraulic conductivity between different soil layers indicates that the improvement of soil by vegetation was limited to the shallow layer,and the parent material in the lower layer can be improved by compounding.The best compounding ratios were 1:1:1 and 1:3:1(loess: aeolian sand: feldspathic sandstone).In which aeolian sand could provide good water conductivity,loess could provide high clay and silt content to enhance aggregate stability,and feldspathic sandstone could enhance water holding capacity.The higher content of large aggregates and organic matter,the better the stability of aggregates,the stronger the infiltration capacity of aeolian sand and feldspathic sandstone.The higher content of sand and organic matter,the lower the content of clay and silt,the stronger the infiltration capacity of loess soil.