Optimization of Cropping Pattern Using Linear Programming Method and Lingo software in Dehgolan Plain in Kurdistan Province, Iran

The optimal allocation of available production resources to the activities that bring the most benefit to farmers and also minimize water consumption, is one of the most important issues in agriculture management where disregarding this issue leads to inefficiency in the agricultural production system. Therefore, in this study; Linear programming has been used to allocate the optimal water resources as well as optimal cropping pattern in Dehgolan plain (Kurdistan province). Lingo software version 14 was used to run the linear programming model. Linear programming ran in 7 modes considering water constraints, cropping pattern, workforce, reduction in groundwater consumption, and minimizing water consumption to determine the optimal cropping pattern as well as a suitable solution for increasing net profit and water productivity. In addition, optimal cropping patterns were assessed in order to minimize water consumption. In general, the results of the current study showed that the net profit of these assessed seven scenarios increased 7.92 to 400 percent in comparison with the current cultivation pattern, while most of the scenarios considered both changes in the cropping pattern and minimizing water consumption. In the scenario of groundwater reduction, despite water availability decreased, the net profit compared to the current situation increased by 10.11%. Accordingly, it can be concluded that during the shortage of available water, such as droughts or applying the strategy of utilizing less groundwater to compensate for the groundwater withdrawal, economic benefits still can be increased along with decreasing water consumption by changes in cropping patterns. The results of this study indicated that optimization of cropping patterns is crucial for economy and water consumption purposes. Unfortunately, farmers in Dehgolan plain do not use available resources in optimal mode at present.
Extended Abstract
1-Introduction
​The allocation of limited available lands to the activities that bring the most benefit to farmers and also minimize water consumption is one of the key issues, and unawareness leads to inefficiency in the agricultural production system. The problem of water scarcity affects most of arid and semi-arid regions. Main parts of the Qorveh-Dehgolan plain, in Kurdistan province, formerly used as rain-fed agriculture and limited lands, were irrigated by surface water. However, these days, along with the exploitation of groundwater resources through wells, parts of the rain-fed lands have been converted to irrigate lands leading to a severe decline in the groundwater table in the last decade. Therefore, the groundwater level has decreased up to 70 meters in some areas of Qorveh-Dehgolan plain.​
2-​Materials and Methods
​Linear programming is used to optimally allocate water resources as well as cropping pattern in Dehgolan plain, Kurdistan province. Lingo software version 14 has been used to run the linear programming model. To find out the optimal cropping pattern, as a suitable solution for increasing net profit and water productivity, linear programming were run in 7 modes including:
1) Optimization without any constraints;
2) Optimization subjected to water constraints;
3) Optimization subjected to water and cropping pattern constraints;
4) Optimization subjected to water, cropping pattern and workforce constraints;
5) Optimization subjected to increase in workforce by 10 % of the current workforce;
6) Optimization subjected to the scenario of a 20% reduction in groundwater consumption;
7) Optimization subjected to minimizing water consumption.
​3-Results and Discussion
​​In the first scenario, the potato crop is the only proposed crop due to higher profitability, where 112603.8 hectares of agricultural lands in the region allocated for the cultivation of this crop. Running the model for the second scenario showed that the net income of this scenario decreased by 57.9% compared to the first scenario, where water consumption decreased up to 85%. The area proposed for potato and rain-fed chickpeas in the fourth scenario in comparison with the current situation were increased up to 80.66 and 31.53%, respectively. In addition, the net profit of the fourth scenario has increased up to 10.98% compared to the current situation. The fifth scenario compared to the current situation showed an increase in the area under cultivation of rain-fed chickpeas and potatoes up to 47.03% and 80.66%, respectively. Also, the net profit of the fifth scenario increased by 11.56 percent in comparison with the current situation. In the sixth scenario; where the groundwater consumption reduced more than 20%, the optimal solution was not obtained. In this scenario; the area under cultivation of irrigated chickpeas, potatoes, and rain-fed chickpeas were increased compared to the current situation up to 98.8%, 38.91%, and 31.99%, respectively. For such a situation, the area under cultivation of other crops decreased and the net profit increased by 10.11% compared to the current situation. In the seventh scenario, the area under cultivation of irrigated chickpeas, potatoes, and rain-fed chickpeas has been increased by 11728, 56.44, and 4.82%, respectively. The area under cultivation of other crops decreased and the net profit of this scenario increased up to 7.92% in comparison with the current situation.
​4-Conclusion
​There is a possibility to increase the net profit of the current cultivation pattern up to 10% by optimizing the available water and land resources in the study area. In the scenario of groundwater reduction, despite water availability decreased, the net profit compared to the current situation increased by 10.11%. Accordingly, it can be concluded that during the shortage of available water, such as droughts or applying the strategy of utilizing less groundwater to compensate for the groundwater withdrawal, economic benefits still can increase along with decreasing water consumption by changes in cropping patterns. Only in the second scenario, water input has a shadow price and showed that providing one additional unit of water increases farmers' profits up to 771 Tomans. In general, the results of this study declared that farmers currently did not use available resources optimally and there is a great potential to increase profits by reallocating resources. According to the findings of this study, linear programing model proposed that the area under cultivation of Medicago reduced equal to 31.73% to minimize water consumption, which is related to the high water needs of this crop.​     
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