water-salinity production function of kochia in the north of golestan

abstract in order to optimize the water management in agriculture in semi arid and arid conditions water-salinity function should be evaluated. in order to evaluate salinity and deficit irrigation two experiments were conducted in 2008 and 2009. kochia was grown with six levels of saline water (1.5, 7, 14, 21, 28, and 35 ds/m) and three levels of applied water (25, 75, and 125 percent of the water requirement) in 2008 and four levels of applied water (50, 75, 100, and 125 percent) in 2009. data were analyzed using linear, quadratic, cobb-douglas and transcendental functions. results showed that quadratic function estimated yield better under salinity and water stress. marginal rate of technical substitution showed that water salinity and water supply can be substituted with the other in a wide range in order to achieve equal amount of yield. marginal production of water quantity and quality were 6.7 and 154 kg.ha-1 in 2008 and 4.8 and -511 kg.ha-1 in 2009, respectively.