Zoning the Soil Affected by Wastewater Irrigation with Using IDW Method (Case Study, South of the Rey City)

Recently the limitation of water resources and necessity of using unusual waters is among the most important issues, especially in dried and semidried area. Less attention to water quality standards can led to less soil quality and reducing theirs functions. This study was done to investigate the spatial distribution of soil fertility characteristics including: pH, phosphorus, nitrate, organic carbon and electrical conductivity. For obtaining maps of the spatial distribution, sampling was done from 57 points in two difference depths, first (0-30 cm) and second (30-60 cm) in 1200 hectares of study area, with using systematic random sampling. To creating the maps, the GIS software V 9.3, was used. The resulted map of the spatial distribution of pH in the two depths indicates that according to standards of Soil and Water Research Institute, at the studied area the limitation of alkalinity is high. Also the results of spatial distribution maps for phosphorus indicates that 360 hectares of study area at depth 1, and 330 hectares at depth 2, has concentrated more than 15 mg kg,-1 , which is more than acceptable range, according to standards of Soil and Water Research Institute. Furthermore the results of spatial distribution maps for nitrate at two depths indicated that concentration of nitrate in study area was not more than acceptable standard, but its concentration is increased from north up to south. In addition maps of spatial distribution for changes in organic carbon at two depths showed that the amount of this parameter is suitable according to standards of Soil and Water Research Institute. Finally the results of electrical conductivity showed that the amount of this parameter at two depths in whole studied area, except in small area, is not more than acceptable amount.