Pedosphere 20(1): 55--62, 2010
ISSN 1002-0160/CN 32-1315/P
©2010 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Estimating van Genuchten model parameters of undisturbed soils using an integral method
HAN Xiang-Wei1,2, SHAO Ming-An2 and R. HORTON3
1 Arid Land Research Center, Tottori University, Hamasaka Tottori, 1390, 680001 (Japan)
2 State Key Laboratory of Soil Erosion and Dry-land Farming on the Loess Plateau, Institute of Soil and Water Conser-vation, Chinese Academy of Sciences, Northwest A&F University, Yangling 712100 (China)
3 Department of Agronomy, Iowa State University, Ames, Iowa 50011 (USA)
      The van Genuchten model is the most widely used soil water retention curve (SWRC) model. Two undisturbed soils (clay and loam) were used to evaluate the accuracy of the integral method to estimate van Genuchten model parameters and to determine SWRCs of undisturbed soils. SWRCs calculated by the integral method were compared with those measured by a high speed centrifuge technique. The accuracy of the calculated results was evaluated graphically, as well as by root mean square error (RMSE), normalized root mean square error (NRMSE) and Willmott's index of agreement (l). The results obtained from the integral method were quite similar to those by the centrifuge technique. The RMSEs (4.61 × 10-5 for Eum-Orthic Anthrosol and 2.74 × 10-4 for Los-Orthic Entisol) and NRMSEs (1.56 × 10-4 for Eum-Orthic Anthrosol and 1.45 × 10-3 for Los-Orthic Entisol) were relatively small. The l values were 0.973 and 0.943 for Eum-Orthic Anthrosol and Los-Orthic Entisol, respectively, indicating a good agreement between the integral method values and the centrifuge values. Therefore, the integral method could be used to estimate SWRCs of undisturbed clay and loam soils.
Key Words:  horizontal infiltration, normalized root mean square error (NRMSE), root mean square error (RMSE), water retention, Willmott’s index
Citation: Han, X. W., Shao, M. A. and Horton, R. 2010. Estimating van Genuchten model parameters of undisturbed soils using an integral method. Pedosphere. 20(1): 55-62.
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