Evaluation of different spatial estimating on estimating soil salinity, pH and CaCO3 percentage (Case study of Boukan region)

Understanding distribution of physical and chemical soil parameters is very important in recognizing, planning, and soil and water resources management in precision agriculture. Regard to the problems related to direct measurement, finding solution to estimate these parameters are very essential. The purpose of this study was to evaluate the spatial variation of some soil parameters such as; soil salinity, pH and CaCO3 percentage using different methods of interpolation and then to select the most suitable method for estimation of the proposed parameters in the Boukan region with total area 2992 Km2. Totally, 183 soil samples were taken from 0-30 cm soil depth in order to cover whole studied area and the amount of salinity, pH and CaCO3 percentage were measured in all soil samples. Then, different interpolation methods (kriging, cokriging, weighted moving average with powers of 2, 3, 4 and 5 and TPSS with powers of 2, 3, 4 and 5) with ArcGIS and GS+ software were used to analyze data. The proposed methods were evaluated by MAE (Mean Absolute Error) and MBE (Mean Bias Error) statistics indexes. The results of this study showed that the cokriging method with minimum MAE 0.218, 0.156 and 7.353 for salinity, pH and CaCO3 percentage respectively, is the most accurate method.