Prediction and Error Analysis of Moisture Characterisitvs Parameters of Soil at Different Sampling Density

Generally,van Genuchten model(VG model) is used to study soil water retention curve(h-θ curve).Soil was sampled at different precision,and soil texture(sand,silt,clay content) and bulk density were used as inputs to predict soil water retention curve parameters of depths(0-20 cm) in top-soil by bagging artificial neural networks,which is based on pedotransfer functions.Furthermore,soil samples collected from watershed of Chenggou in Gansu Province were used to predict soil water retention curve parameters and to analysis on their bias.The results indicated that linear regression could be used to reduce the bias of prediction parameters and tested parameters;the accuracy of predicting saturated volumetric capacity was better than the accuracy of predicting soil available water capacity and field moisture capacity by BP artificial neural networks.