Evaluation and Comparison of Ordinary Kriging and Inverse Distance Weighting Methods for Prediction of Spatial Variability of Some Soil Chemical Parameters

Analysis and interpretation of spatial variability of soils properties is a keystone in site-specific management. The objective of this study was to determine degree of spatial variability of soil chemical properties with Ordinary Kriging (OK) and Inverse Distance Weighting (IDW) methods. Spatial distributions for 6 soil chemical properties were examined in a fallow land in Bajgah, Fars province, Iran. Soil samples were collected at approximately 60 0 m grids at 0-30 cm depth and coordinates of each of the 100 points were recorded with GPS. Kriging and inverse-distance weighting are two commonly used techniques for characterizing this spatial variability and interpolating between sampled points. Data were interpolated with OK and IDW with powers of 1-5. All studied soil chemical parameters were strongly spatially dependent, but the range of spatial dependence was found to vary within the soil parameters. Phosphorous had the shortest range of spatial dependence (49.50 m) and pH had the longest (109.50 m). The accuracy of OK predictions was generally unaffected by the coefficient of variation. We concluded, for all soil chemical properties, OK performed much better than the five IDW procedures in this study.