Predicting and Mapping of Soil Hydraulic Properties in Karnataka

Abstract

Field capacity (FC) and permanent wilting point (PWP) are the two vital hydraulic properties that determine the availability and retention of the water for plant growth. In the present study, profile FC and PWP were mapped in Karnataka using 5352 soil profile datasets. Class pedotransfer function was developed based on soil texture classes, and the total profile FC and PWP were computed for 1 m soil depth. Primary and secondary terrain attributes, vegetation indices, lithology and climatic datasets were used as environmental covariates for the prediction of hydraulic properties. Random forest regression kriging model was calibrated using 80% of total datasets and validated using 20% of datasets. Root mean square error (RMSE), mean error (ME) and the coefficient of determination (R2) were calculated to assess the performance of models. The model recorded RMSE of 127 mm for total profile field capacity (TFC) and RMSE of 87 mm for total profile permanent wilting point (TPWP). The predicted TFC and TPWP in Karnataka are ranged from 58 to 521 mm and 35 to 342 mm, respectively. Available water content (AWC) was calculated as the difference between TFC and TPWP, and the results showed that northern Karnataka has lower AWC (< 50 mm) compared to the south and western part of Karnataka. The present high-resolution (250 m) maps of TFC and TPWP are useful for irrigation scheduling, land use planning and different crop modeling studies.