Soil salinity is a measure of the total amount of soluble salt in soil. Assalinity levels increase, plants extract water less easily from soil,aggravating water stress conditions. This study was carried out todetermine salinity threshold value and slope of the yield decrement forwheat. In this research SWAP model was study for an arid regionlocated in central part of Iran including 94 villages belonged toirrigation network of Garmsar district. The data collected from theabove 94 villages for ...