Verification of Soil Moisture Simulating Accuracy on Dry-Land Winter Wheat and Spring Maize Field by EPIC Model on the Loess Plateau of China

Abstract

EPIC model is an effective tool to simulate soil water which is the key factor to influence the crop production on the Loess Plateau of China. So there is a practical meaning to evaluate the simulation results of soil water. In Loess Plateau amount of rainfall varies greatly throughout the year. So it’s annually and monthly distribution has a great significance for the development of crop production and recovery of soil moisture in different layers. In this study, the accuracy of simulated monthly soil moisture was assessed, based on measured monthly soil moisture (0-2m soil layer) data from 1987 to 1996 at Changwu Agricultural Station. Results showed that RRMSE (Relative Root Mean Square Error) between simulated and measured soil moisture (0-2m soil layer) in winter wheat field and spring maize field was 2.8% and -0.2% respectively, the value for RMSE (Root Mean Square Error) was 0.023m/m and 0.015m/m respectively. The accuracy of simulated soil moisture influenced by the precipitation amount of simulated years were lower in extreme rainfall years (extreme rainy years and extreme drought years) than in other rainfall years. Therefore, the modified EPIC model predicted well soil water in different soil layers and provided basis for the EPIC users to research the law of soil moisture changes in arid cereal land at Changwu arid-plateau. If reasonable crop database, soil database and meteorology database are built up into the EPIC model, the accuracy of simulated soil moisture will be increased.