برآورد تقاضای آب در تولید محصول یونجه (مطالعه موردی شهرستان‌های قروه و دهگلان)

Water is one of the most valuable natural resources in the world, which will be in demand by various sectors. Water deficit is one of the important challenges of environmental crisis in the Middle East, including Iran. The agriculture sector is the largest consumer of water by irrigated agriculture in every region that is intensified because of consecutive droughts in recent years. One of the methods for managing this crisis is water pricing that uses the economic value of water in agriculture sector. Farmers pay far less than the real price of utilization water in the agricultural sector. They also pay lower taxes for water than other nonfarm consumers. Therefore, the allocation of water among farmers is inappropriate. This mechanism is the main reason of non- optimal use of water and it led to excessive extraction of water resources.
Qorveh and Dehgolan townships are the main agricultural region of Kurdistan Province. They are producing a quarter of the province's agricultural products and 42000 tons of Alfalfa produced annually in these regions. As these have the second rank in producing Alfalfa over the country. In addition, given the high number of livestock, factories and dairy industry need to hay crops, especially alfalfa for grown in the province of Kurdistan.
In this study, the data were collected via 100 questionnaires that completed by farmers and plantation owners by authors and utilized stratified sampling in 2010-11 year. The Cochran sampling method is used to calculate the sample size. In the present study, flexible and non-flexible functions including Translog Production Function, Generalized quadratic Production Function, Generalized Leontif Production Function, Transcendental Production Function and Cobb– Douglas Production Function were investigated for determining the best model to estimate the shadow price by some test and statistics. The results showed that the Cobb - Douglas function had better performance than other considered functions. This function has more suitable form relative to other functions. R2 and F statistic were used to evaluate the goodness of estimates and significance of the regression in five considered functions, respectively. Based on the JB statistic the distribution of error correction functions is Normal. In addition, the maximum likelihood test was used to compare the Cobb – Douglas Production function as conditioned function and other functions as non-conditioned functions. The values of LR statistics confirmed the superiority of Cobb-Douglas function than other considered functions. According to the above-mentioned criteria, it can be concluded that the Cobb-Douglas function form is more suitable than other functional forms for investigating alfalfa crop production in the study area. The MP will be achieved from the coefficients of the variables in the equation of the above function. Based on the results, inputs such as seeds, fertilizers and cultivated area have positive elasticity, so they consume in optimal region. But labor, water, machinery and pesticides have negative elasticity, due to the excessive consumption of these inputs. Therefore, these inputs are used in the non-optimal and non-economic in alfalfa products. Then, the consumption of these inputs must decrease. The highest and lowest average productivity belonged to the cultivated area and water. Marginal productivity show cultivated area and seed inputs are used efficiently. Also, other inputs, especially used water are inefficient consumption by farmers. This result confirms the obtained previously outcomes. Also water pricing for farmers is 28.51 Rails per cubic meter while the estimated economic value is 84.94 Rails per cubic meter in the study area. Thus, farmers have to pay only 30 percent of the economic value of water. In this study, as well as studies in the mountainous region, that conducted by Ahmadpor and sabouhi (2009) and Ehsani and et al (2010), the market price and water economy is low. Because, the water price which government takes from farmers is lower than the real price to promote sprinkler irrigation system in the region. The other reasons are that the Ghorveh and Dehgolan Townships are located in a mountainous region which the water deficit is not serious and important. The above factors caused the lake of the markets and economy water in this area. Also the obtained price elasticity is equal to -2.59 and it is less than minus one, which indicates the importance of this pricing policy to control excessive water consumption .Price policies could be an important factor in controlling Non- optimal consumption of water in the world.
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