Determine the optimal production functions of wheat in arid areas (Case Study: Southern Khorasan in Iran)

Water shortage and qualitative decrease of water sources and soil in southern Khorasan province (in east of Iran) are the major causes of decreased production. This research intended to investigate the production of wheat cultivars in salinity and deficit irrigation conditions. The determination of water-salinity optimum production, itsfunction for wheat varieties, obtaining water use efficiency under these conditions by means of production assessment indicators, and providingiso-yield curves for wheat varieties, in order to apply for agricultural water resources management programming in Southern Khorasan werecarried out in farming years 2013-2014. The research program consisted of three levels of the salinity of irrigation water (S1, S2, S3 =1.4, 4.5,9.6 dS/m, respectively), two wheat varieties (Ghods and Roshan) and four levels of irrigation water (I1, I2, I3, I4 =26.7, 40.1, 53.4, 66.7 cm,respectively). The experiment had three replications according to a randomized complete block design with split plot layout (factorialform), which considered water quality as main plot and water quantity as sub plot. Then, obtained data were estimated based on differentforms of production functions (Linear, Cobb-Douglas, Quadratic and Transcendental) and data value .Optimum production function for eachwheat variety was also estimated which led to the following results: First, quadratic production functions for both Ghods and Roshan wheatwere recognized as optimum production functions in Birjand region. Second, it was recommended to irrigate the wheat in this region on thebasis of 75% of water requirements, and devote the preserved 25% water to neighboring areas. Third, the effect of deficit irrigation ondecreasing the production was more than that of the salinity of irrigation water, and the total effects of salinity and deficit water together were less than the sum effects of each factor in isolation. Fourth, the investigation of production assessment indicators showed that, in all level treatments, Roshan wheat in relation to both salinity and water deficit might be proved to be more resistant than Ghods wheat.

Keywords:

Birjand , Salinity , Yield function , Water shortage , Wheat