Using OK and IDW Methods for Prediction the Spatial Variability of A Horizon Depth and OM in Soils of Shahrekord, Iran

Abstract

This study attempts to evaluate some interpolation techniques for mapping spatial distribution of A horizon depth and OM in Shahrekord, Iran. 15000 hectares of South West Shahrekord soils were studied in which totally 92 soil profiles were excavated and classified according to USDA. The performance of methods was evaluated by RMSE, ME and R². Calculated RMSE for depth of A horizon were 0.01074, 0.19670 and 0.19858, respectively by IDW and OK (with Spherical and Exponential models). The RMSE for surface horizon OM were obtained 0.05593, 0.12121 and 0.05078, respectively by IDW and OK (with Spherical and Exponential models). The results showed that IDW could estimate the variability of A horizon depth and Ok (with Exponential semivariogram) could estimate the variability of depth of A horizon more better than other methods. The weakness of kriging in prediction of spatial continuity of depth of A horizon is due to effects of variability of soil forming factors in evolution of soils evolved in different landforms of study area which could take out the stationary assumptions.

Keywords: Ordinary Kriging, Inverse Distance Weighting, Evaluation of models