Analyzing the Geostatistical Methods in Spatial Monitoring of Saline and Sodic Condition of Soils under Treated - Wastewater Irrigation

Unmanaged use of natural resources such as soil would lead to deterioration of its quality and fertility. Consequently, spatial monitoring of these properties is necessary to find the optimal management options to protect soil fertility. Thus, in this study, the long-term effects of treated wastewater irrigation on qualitative properties of surface soil layer were spatially monitored using geostatistical methods and were compared with worldwide standards. Consequently, the soil qualitative properties including sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), electrical conductivity (EC) and acidity (pH) was analyzed in pixels with 150×105 meter dimension and the possibility of extracting raster maps using weighting moving average (WAM), kriging and co-kriging methods was investigated. Results showed that kriging and WMA had the least estimation error for ESP and the other parameters, respectively, based on the evaluating indices. Also using covariates does not have positive effect on increasing range of influence and interpolation accuracy. Comparing the prepared raster maps by the selected method with the standard values of Soil Survey Manual of USA showed that unmanaged use of unconventional water caused more than 97% of the study area to have saline soils. Also, hazard of sodium in the soils dominated to salinity problem in more than 94% of the study area. These could have irreparable damages under water crisis through degrading soil structure. In conclusion, for sustainable agriculture and food security in the study area it is necessary to offer management options for soil improvement such as leaching in uncultivated seasons or combined irrigation with fresh water to protect economic and environmental issues