Deriving crop production functions to estimate wheat virtual water and irrigation water price

Wheat is one of the most strategic agricultural crops across the word and its production plays a significant role in human nutrition. Water resources scarcity and sequential droughts events in Iran are two challenging issues in providing water for strategic crops such as wheat. In the other hands، large amount of wheat is annually imported to the country which needs more attention to wheat virtual water and its economy. The objectives of this study were to determine the amount of green and blue virtual water of wheat، irrigation water price and virtual water flow in Iran and in particular in Fars province for ten consecutive years. Consequently، the cultivated areas، crop production and precipitation data were collected for the period of 2000 to 2010. The potential evapotranspiration of wheat for every province was obtained using NETWAT package. Calculating the actual evapotranspiration with FAO crop water production function، the effective rainfall as well as the blue and green virtual water and irrigation water price were determined. Results indicated that changing the land use from dry to irrigated farming and mismanagement of water and soil resources as well as disregarding the climate have increased the irrigated area، virtual blue water and costs being followed by decreasing dry farming cultivation area، virtual green water and crop yield in Fars province. Although the irrigated areas were increased in last two years in the country scale، the irrigated yield was reduced which increased virtual blue water and costs. There exists no scientific، economic، environmental and practical justification for such consequences and the costs which imposed on the government and people are not returnable.