Spatial variability of soil properties and its application in predicting surface map of hydraulic parameters in an agricultural farm

Knowledge of spatial variation of soil properties is important in precision farming and environmental modelling. Spatial distribution of water content at field capacity (FC) and permanent wilting point (PWP) at different zones of a farm governs the available water for plant growth. These two soil hydraulic parameters play key roles in crop selection for different blocks of a farm, and in scheduling irrigation of crops in a field. In this study, spatial variation of bulk density organic carbon, silt and clay contents for two soil depths (0–15 and 15–30 cm) in the agricultural farm of the Indian Agricultural Research Institute, New Delhi were quantified and the respective surface maps were prepared through ordinary kriging. Particle size distribution shows better spatial correlation structure than bulk density and organic carbon content. Gaussian model fits well with experimental semivariogram of bulk density, and silt and clay contents. Hole-effect model was found to be the best to fit the experimental semivariogram of organic carbon content. Spatial correlation structure for both surface (0–15 cm) and subsurface (15–30 cm) soil layer remains the same, but the magnitude of spatial correlation differs. Crossvalidation of the kriged map shows that spatial prediction of basic soil properties using semivariogram parameters is better than assuming mean of observed value for any unsampled location. Pedo-transfer functions were coupled with the surface map of basic soil properties to generate a map of water content at FC and PWP. Evaluation of spatial maps of θFC and θPWP showed reasonable accuracy of these two hydraulic parameters for farm-level or regional-scale application.