مرجـع دانـش پارس

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 years 1998 to 2007 were used to calibrate andsimulate yield of wheat using the SWAP model. The irrigation watersalinities of 2, 4, 6 and 8 dS m-1 were used and yield reductions versussoil saturation extracts were evaluated and salinity threshold value andslope of the yield reduction were determined. The results showed thatthe SWAP model predicts crop yield with good accuracy and thethreshold value and slope of the yield reduction is site dependent