A Comparison of Interpolation Methods for Preparing Soil Quality Maps: Case study: (Agricultural Faculty

Population growth rating, high food demand, and land resource challenges have led to more serious studies of production factors especially the scarce water and soil resources. One of the most basic data items in land resources is the soil map. Therefore, in the process of the present research for preparing soil maps of some soil quality indices at the Faculty of Agriculture Experimental Field (located in the southern part of Karaj city, Tehran) sampling of soil was carried out in 500×500 m grids. Following data normalization, the variograme was developed. For interpolation of soil parameters, Kriging, Cokriging as well as IDW methods were employed. The most appropriate model for interpolation was selected by means of cross validation and error evaluation methods, using RMSE. The results revealed that Cokriging is a more appropriate method than the others for prediction of some such soil properties as Cu, Zn, Mn, Pb, OC and CaCO3 because it was a method developed for limited number of sample cases. As for the rest of soil parameters, IDW was of the lowest number of errors and therefore, was selected as the fittest method for interpolation. Soil characteristic maps were finally prepared, using the most appropriate interpolation methods in GIS environment.