تخمین تابع عرضه و تقاضای محصولات کشاورزی حوضه آبریز هیرمند

برآورد عرضه و تقاضای بخش کشاورزی و شناخت عوامل موثر بر آن می‌ تواند موجب کارآتر شدن سیاست ‌ها و برنامه ‌ریزی ‌ها در این بخش شود. هدف اصلی مطالعه حاضر شناسایی سیاست ‌های مورد نیاز برای تعادل عرضه و تقاضای محصولات کشاورزی منطقه سیستان بود؛ و بدین منظور، متغیرهای تاثیرگذار بر عرضه و تقاضای محصولات کشاورزی سیستان در حوضه آبریز هیرمند طی دوره زمانی 97-1379 با استفاده از نظام معادلات هم‏زمان به روش حداقل مربعات سه ‏ مرحله ‌ای بررسی شدند. یافته‌ های تحقیق نشان داد که در بخش کشاورزی، عواملی چون سطح زیر کشت زراعی و باغی، نیروی کار، سرمایه، تقاضای آب و نیز قیمت محصولات کشاورزی اثر مثبت و معنی‌ دار بر عرضه محصولات کشاورزی داشته‌‏اند؛ همچنین، اثر عوامل جمعیت و درآمد حاصل از بخش کشاورزی بر تقاضای محصولات کشاورزی مثبت و معنی ‌دار و اثر قیمت محصولات کشاورزی بر تقاضای محصولات کشاورزی منفی و معنی‌ دار بوده است.

estimation of supply and demand function of agricultural products in hirmand catchment of iran

introduction: the agricultural sector plays a key role in the economic planning of any country and is of prime importance to its economic and social development. one of the goals of this sector is to achieve a sustainable production growth as well as a productivity growth. the most pressing need of people is the availability of food community, the sole provider of which is the agricultural sector. shortages or fluctuations in crop prices have been one of the major problems in iran’s economy, causing discontent for most people in the community, which is challenging the authorities, including officials’ concerns about the stability of agricultural commodity prices in the market. in this study, factors affecting supply and demand of agricultural products in hirmand catchment in sistan region of iran were investigated. given the importance of supply and demand of agricultural products in this region, identifying the factors influencing the supply of products is necessary to implement effective policies in line with government decisions to expand the supply of agricultural products. thus, the factors and variables affecting the supply and demand of agricultural products in the region can influence the factors and variables affecting the supply and demand functions of agricultural products.materials and methodssimultaneous equations system: in this model, an endogenous variable is a function of another endogenous variable, which also requires the introduction of another equation. accordingly, instead of a multi-equation equation (system of equations), these conditions violate the ordinary least squares (ols) assumption. a simultaneous equation system is used when there are several dependent variables that are interdependent, so a system of equations or multiple equations is defined. results and discussion: according to the study results, the variables entered in the agricultural supply model of sistan region in hirmand catchment explained the variation of dependent variable by 0.97 percent and the statistical value is 1.62. there was a positive and negative correlation while all the coefficients of the variables were significant at the one percent level; in addition, the crop and garden area coefficients, agricultural labor force, agricultural capital, water demand, and stable crop prices were estimated 1.20, 3.41, 0.95, 9.15, 0.0004, and 3.36, respectively. based on the estimated results, the demand function of agricultural products was statistically significant. demand for agricultural products is a function of crop prices, agricultural income and population, which the coefficient of crop price demand function was estimated negative (-30.84) while those of population and income of the agricultural sector were found to be positive (1.339 and 5.55, respectively).conclusion: analysis of model estimation results showed that there was a significantly positive relation between supply and demand of agricultural products, indicating that the agricultural supply is a function of crop and garden cultivation area, labor force, capital, water demand and agricultural price. the greatest impacts were on the variables of capital, cultivation area and agricultural price on the agricultural supply. therefore, increasing any of these variables may cause changes in the supply of products.