evaluation of the economic changes of planting pattern resulted from sugar beet planting area variation (case study: qazvin plain)

sugar beet is one of the major products in qazvin plain that allocated most of planting areas to itself after wheat, barley and corn. in recent years, restriction on water resources decreased sugar beet planting area in this plain. therefore, in this study, the effects of increase in sugar beet planting area on planting pattern, grower's gross profit, and inputs utilization under water shortage was investigated. to achieve this goal, positive mathematical programming model and products yield function based on water requirement was used. data were collected from the questionnaires completed by 127 growers in 2012-13. data were analyzed by spss software and the model was solved by gamz software. results showed that increase in sugar beet planting decreased wheat, barley and canola planting area and increased the grower's gross profit. it also resulted in reduction in inputs utilization such as water, capital, and machines in large fields and increase in utilization of the aforesaid inputs for small and medium fields. in conclusion, increasing sugar beet planting area which resulted in reduction in fertilizer and pesticide application is recommended as a proper solution for reducing environmental pollution in southern regions of qazvin plain.