Evaluation of soil water retention pedotransfer functions for Vietnamese Mekong Delta soils

Abstract

Appropriate management of irrigation and drainage, which require the information of soil water retentioncharacteristics (SWRC), is of crucial importance for sustainable paddy rice production in tropical deltas.SWRC, however, is usually missing due to the lack of facilities, cost, and personnel training involved indirect measurement methods. Pedotransfer functions (PTFs) that provide the estimation of SWRC fromother basic soil properties are the alternative source of SWRC for practical soil water managements ormodeling purposes. Since developing new PTFs is a very arduous task which requires a large soil databaseof good quality, utilizing existing PTFs where possible is highly recommended. The objective of this studywas therefore to evaluate the applicability and reliability of published SWRC-PTFs for soils in tropicalVietnamese Mekong Delta (VMD) where paddy rice is the main agricultural practice. A number of well-known statistical regression and pattern-recognition PTFs were selected for the evaluation. By assessingthe correspondence between measured and PTF predicted values of SWRC, the results show that the PTFsderived from large databases of soils in the regions having similar climatological and pedological condi-tions to VMD soils are more reliable for predicting SWRC (RMSE varies in the range of 0.06–0.07 m³ m−³, and of 0.05–0.06 m³ m−³ for the prediction of soil water content at −33 kPa and −1500 kPa, respectively).The applicability index together with geographical information, therefore, could be used as integral indi-cators to select appropriate PTFs in cases no SWRC data are available for timely uses. Detailed evaluationof PTFs’ performance however revealed the limited potential of investigated PTFs to VMD soils. Furtherresearches to develop specific PTFs for tropical delta soils are recommended for accurate SWRC estimationin such regions.