Effect of Salinity and irrigation regimes on Biomass Production of Kochia (Kochia scoparia) and Trend of Soil Salinityý.

In order to evaluate saline water and water scarcity effect on growth parameters, water-salinity production function and physiological parameters in field conditions, an experiments was conducted based on randomized complete block design by split plot arrangement where salinity as a main plot and water deficit as a subplot with three replications . Treatments were six levels of saline water (1.5, 7, 14, 21, 28, 35 and 42 dS m-1) and four levels of applied water (50, 75, 100, and 125 percent of full irrigation). Results showed that Kochia is sensitive to saline water at the earliest stages of growth, and the best plant height to start saline irrigation is between 10 and 15 cm plant height. It produced remarkable amounts of dry biomass 34 t ha-1 under suitable conditions (1.5 dS/m).Under severe drought and salinity (42 dS/m), kochia still could produce up to 16 t ha-1 biomass. Salinity tolerance of kochia was improved by increasing water application. Results of water depletion from different soil layers showed that kochia uptakes more water from the 30-60 cm soil depth under saline condition. The soil salinity (ECe) of this section was lower in comparison to the 0-30 cm soil depth. Additionally, the water uptake of the 30-60 cm soil depth improved the salt tolerance level of Kochia. Salinity reduced linear phase of growth and decreased biomass production. The effect of maximum crop growth rate was higher than maximum crop growth duration on biomass production. Green biomass index of Kochia increased compared to shoot biomass and ameliorated the reduction of the net assimilation rate. Salinity reduced water productivity and crop coefficient. Evaluation of yield response factor under water deficit and salinity showed that up to 21 dS/m there are not any significant differences among water deficit treatments, and then water deficit management can be used in Kochia. Kochia s root can selectively absorb and transport of Na+as well as K+ and by accumulating Na+ in root media, selective absorption of K+ was increased and maintained the Na/K ratio in plants. 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 4.8 and -511 kg.ha-1, respectively.