Assessment of the SOILWAT model for predicting soil hydro-physical characteristics in three agro-ecological zones in Nigeria

Abstract

Soil hydro-physical characteristics influence soil nutrients availability and consequently affect crop performance. However, field determination of these properties for effective management of water for irrigation is laborious, time consuming and expensive. Hence, this study was initiated to assess the performance of the SOILWAT model for the estimation of soil hydro-physical properties. A total of 180 disturbed and 120 undisturbed soil samples were collected from three agro-ecological zones (Savannah, Derived savannah and rainforest) in Nigeria. The samples were analyze for hydro-physical and chemical properties. Soil texture and salinity data were varied in the SOILWAT model (Version 6.1.52) to predict soil physical properties for the three agro-ecological zones of Nigeria, respectively. Measured and predicted values of field capacity, permanent wilting point and soil available water were compared using T-test at α.05. The prediction of soil textural class using the SOILWAT model was sufficiently accurate for the three agro-ecological zones. However, bulk density, maximum water holding capacity, permanent wilting point and soil available water showed significant (p < .05) differences between measured and predicted values, and there were positive relationships between SOILWAT values and the observed values. Thus, the SOILWAT model could be adopted for predicting soil texture and permanent wilting point for savannah, derived savannah and rainforest zones of Nigeria. Also, the inclusion of organic matter input, silt adjustment and addition of salinity in the various moisture characteristics relationships and equations could enhance its performance. Keywords: Field capacity, Permanent wilting point, Soil available water, Soil texture, SOILWAT model