Research On Soil Infiltration Of Different Land Use Types In Purple Soil Area

Purple soil is one of the most important soil types in China.It is mainly distributed in 15 provinces(regions)such as Sichuan,Chongqing,Guizhou,Hunan,Yunnan,Guangxi,Jiangxi,Guangdong,Hainan,Hubei,Fujian,Zhejiang and so on,with a total area of approximately 290,000 Km2.The soil erosion is serious in this area,and the modulus of soil erosion can reach as high as 5500~15000t/km2·a,which is one of the areas with the most severe soil erosion in China.The soil infiltration rate is an important parameter to analyze the process of simulating soil erosion,and it is also an indispensable part of soil erosion prevention and control.The infiltration properties of purple soil and its influencing factors have been widely studied,but there are few reports on the quantitative calculation of the matrix and preferential inflow of purple soil.This study takes purple soil slope farmland and grassland of Damotan Village,Xiema Town,Beibei District,Chongqing as the research object.The soil matrix infiltration and total infiltration rate of different land use types in purple soil were quantitatively determined by the surface ring infiltration meters,and the preferential inflow rate was calculated.The differences of soil infiltration performance of different land use types were comparatively analyzed.The Philip infiltration model and Kostiakov infiltration model were used to fit the total infiltration process and matrix infiltration process measured at different test sites.The differences of soil physical and chemical properties of different land use types in this area were analyzed.Linear regression analysis of soil physical and chemical properties of different land use types and the measured soil infiltration rates was conducted by SPSS,and the correlation between soil infiltration performance and soil physical and chemical properties of different land use types was obtained.The results of this study can reflect the infiltration characteristics of purple soil more realistically,and provide some basis and reference for the mechanism of soil preferential flow in the purple soil area.The main conclusions are as follows:(1)The soil infiltration properties of different land use types are different.The soil total initial infiltration rate of corn land is 45.39~75 mm/min,the soil total steady infiltration rate of corn land is 3.39~5.79 mm/min,the matrix initial infiltration rate of corn land is 8.38~32.66 and mm/min,the matrix steady infiltration rate of corn land is3.15~4.20 mm/min,the preferential flow initial infiltration rate of corn land is37.01~42.34 mm /min,and the preferential flow steady infiltration rate of corn land is0.04~1.59 mm/min.The soil total initial infiltration rate of grassland is 27.81~41.18mm/min,the soil total steady infiltration rate of grassland is 5.99~12 mm/min,the matrix initial infiltration rate of grassland is 13.04~15 mm/min,the matrix steady infiltration rate of grassland is 5.69~6.72 mm/min,the grassland preferential flow initial infiltration rate is 14.77~26.18 mm/min,and the preferential flow steady infiltration rate of grassland is 0.30~5.28 mm/min.The indexes of soil infiltration performance of different land use types are different.In the process of matrix infiltration,the initial rate,the steady infiltration rate and the average soil infiltration rate are larger in the grassland.In the process of total infiltration and preferential inflow,the initial rate is larger in the corn field,and the steady infiltration rate and the average soil infiltration rate are larger in the grassland.The ratio of soil matrix infiltration rate to priority inflow rate of different land use types increases with time.In the first 10 minutes of infiltration process,preferential flow dominated,and then matrix infiltration dominated the next 90 minutes.The ratio of cumulative infiltration of soil matrix and cumulative infiltration of preferential flow in different land use types ranged from 0.5 to 2.0,and the soil matrix had the same important role as preferential infiltration in the soil hydrological process in purple soil area.(2)Different infiltration models have different fitting effects on soil infiltration process for different land use types.The total infiltration process of the corn field measured can well characterize the total infiltration characteristics of the soil,however,the total infiltration process of the grassland characterize the total infiltration characteristics of the soil with relatively large errors.The measured soil matrix infiltration process of the corn field and grassland can well characterize the infiltration characteristics of soil matrix.Compared with the Philip infiltration model,the fitting effect of Kostiakov infiltration model is better.(3)The soil infiltration properties of different land use types are quite different,and the physical and chemical properties of soil are the main influencing factors.The correlation of soil infiltration performance to physical and chemical properties of different land use types is very different.The main manifestations were: Soil infiltration performance of corn land was positively correlated with sand content,powder content,soil moisture content,organic matter and porosity,while negative correlated with viscosity content and bulk density.The soil infiltration performance of grassland waspositively correlated with sand content,powder content,organic matter and porosity,while negatively correlated with viscosity content,soil moisture content and bulk density.The infiltration performance of the same land use type soil in different infiltration processes(total infiltration,matrix infiltration,and preferential infiltration)had significant differences in the correlation between infiltration performance and physical and chemical properties of soils.Plant roots and soil thickness are also important influencing factors for the differences in soil infiltration performance of different land use types.