Studies On The Soil Hydraulic Properties And Pedo-transfer Functions In Fengqiu County

Problems of soil water, solute transport and preferential flow have become the central issue of soil physics studies, but it is difficulties to obtain the field data of the parameter of soil hydraulic properties such as water content( 6), saturated hydraulic conductivity(Ks), unsaturated hydraulic conductivity (K( 6 )) and water retention curve of soil(h( 6 )) needed to study those problems in practical works. In this paper, we have studied the fluvo-aqic and erosion sandy soil in Fengqiu county,Huanghuaihai and tried to find the practical and feasible ways to solve problems of the parameter of soil hydraulic properties. The results show as follows. 1. Soil saturated hydraulic conductivity in field was studied by disc- permeameter. Disc~permeameter can measure saturated hydraulic conductivity of soil layer of every depth above ground water level with less time, labor and water than other methods. At the same time, this method could eliminate the negative effect of big holes such as soil crevice, earthworm and root pole on determining saturated hydraulic conductivity. 2. Parameters of four experimental models describing soil water retention curve were determined by least square method and Picard iteration. The results showed that Van Genuchten model had some applicability. 3. Based on a great many of fundamental soil physical properties and soil water-retention data in Fengqiu county, pedo-transfer function models of soil water content, saturated hydraulic conductivity and Van Genuchten model parameters( 6 ~, 6 r?a, n) were established by the use of multivariate stepwise regression analysis respectively. The results showed that soil water content, saturated hydraulic conductivity and parameters of Van Genuchten model had some linear correlation with basic soil physical properties. In water content model, predicting accuracy of soil water content from 0 to -3OkPa potential was enhanced by incorporating one measured soil water content(at -3OkPa potential) as an additional independent variable, and that of soil water content from -lOOkPa to -l500kPa potential was enhanced obviously by incorporating one measured soil water content(at -I 500kPa potential) as an additional independent variable. The fitted effect of soil saturated hydraulic conducti- vity had far from ideal because of experimental errors. The fitted effect of parameter estimation model of Van Genuchten model on clay soil was very well but the effect on sandy soil was not good because of big errors. 82 4. The PTFs model could predict soil saturated water content, residue water content and parameters a,n of Van Genuchten model based on surface soil fundamental physical properties in Fengqiu county by GIS, however, it was not good enough to predict soil saturated hydraulic conductivity. There are few studies on soil Pedo-transfer function in China now, but applying soil pedo-transfer function to determine soil water hydraulic parameters has important role in the studies of soil water, solute transport and field water circulation.