ANALYSIS AND MODEL FITTING FOR PURPLE SOIL WATER RETENTION CURVE UNDER DIFFERENT MEASURES OF SOIL AND WATER CONSERVATION IN THE THREE GORGES RESERVOIR AREA

Soil water retention curve is one of the important soil hydrodynamics parameters in quantitative study of soil water retention and movement,which can reflect the basic properties of soil,such as water retention,water supply,and water availability,et al.In this thesis,characters of purple soil water retention curves under different measures of soil and water conservation were discussed,through analyzing soil water retention curves under contour hedgerow-intercroping system and rock ridge terrace-intercroping system.Then the measured datas were taken to fit four common soil water retention curve models respectively,in order to select the best model for the purple soil in the Three Gorges Reservoir Area.The results showed that the difference of purple soil water retention among different treatments could be observed easily.Based on the same soil water suction,soil water content was the highest for contour hedgerow treatment,secondly for rock ridge terrace treatment,and the lowest for the control.With the increase of soil water suction,the difference among treatments was more obvious.Both Gardner model and van Genuchten model were suitable for expressing purple soil water retention curve.According to practical needs,one of them could be selected.Generally,Gardner model was suitable for simple and quick field soil water management,and van Genuchten model was suitable for soil hydraulic properties estimation and application.