Prediction of Soil Water Retention and Available Water of Sandy Soils using Pedotransfer Functions

Quantitative knowledge of the unsaturated soil hydraulic properties is required in most studies involving water flow and solute transport in the vadose zone. Direct measurement of such properties is often expensive and time-consuming. In this study, extended nonlinear PTF were established and its prediction performance for soil water retention and available water content were compared to those of artificial network for the Aeolian sandy soils at Beigou in Zhangwu country. PTFs were evaluated based on root mean square errors (RMSE) and mean errors (ME) between the observed and predicted values for the following depth intervals (0-20 cm, 20-40 cm). Results showed ENR and ANN with bulk density far underestimated soil water at certain suction with ME values ranging from -0.02 to -0.15 cm3/cm3, while ANN, ANN with soil water at certain suction overestimated soil water at 10 kPa, 33 kPa, 40 kPa and 200 kPa suctionin with ME values ranging from 0.04 to 0.16 cm3/cm3.