Survey and Zoning of Soil Physical and Chemical Properties Using Geostatistical Methods in GIS (Case Study: Miankangi Region in Sistan)

In order to provide a database, it is essential having access to accurate information on soil spatial variation for soil sustainable management such as proper application of fertilizers. Spatial variations in soil properties are common but it is important for understanding these changes, particularly in agricultural lands for careful planning and land management.
To this end, in winter 1391, 189 undisturbed soil samples (0-30 cm depth) in a regular lattice with a spacing of 500 m were gathered from the surface of Miankangi land, Sistan plain, and their physical and chemical properties were studied. The land area of the region is about 4,500 hectares; the average elevation of studied area is 489.2 meters above sea level with different land uses. Soil texture was measured by the hydrometer methods (11), Also EC and pH (39), calcium carbonate equivalent (37) and the saturation percentage of soils were determined. Kriging, Co-Kriging, Inverse Distance Weighting and Local Polynomial Interpolation techniques were evaluated to produce a soil characteristics map of the study area zoning and to select the best geostatistical methods. Cross-validation techniques and Root Mean Square Error (RMSE) were used.
Normalized test results showed that all of the soil propertiesexcept calcium carbonate and soil clay content had normal distribution. In addition, the results of correlation test showed that the soil saturation percentage was positively correlated with silt content (r=0.43 and p 0.01) and negatively correlated with sand content (r=0.48 and p According to the produced maps soil electrical conductivity with coefficient of variation of 102.99 and low effective range (935 meter) showed a very high spatial variability which mostly depended on the soil type of Miankangi region. The content of calcium carbonate with an average of 18.66 percentage a relatively high figure and indicates calcium carbonate precipitation as one of the most soluble salts in the soil.Miankangi soils acidity in the neutral range (8.13) is alkaline. That is due to very low coefficient of variation obtained for pH, alkalinity of soil can be seen from its inherent feature. In addition, the high concentration of dissolved substances in studied soils represents further expansion of salinity in irrigated lands in the study area, which leads to reduce in soil quality and health due to irrigation and fertilization. Accordingly, it needs a proper management, implementation of targeted programs for prevention, and overcoming the salinity problems for the sake of improving the soil quality, as well as, achieving sustainable agricultural development in this region.