جستجوی مقالات مرتبط با کلیدواژه "برنامه ریزی ریاضی اثباتی" در نشریات گروه "کشاورزی"

Due to the limitation of surface water resources and excessive exploitation of underground water, the underground water table in many plains of Iran is in an unfavorable condition. One of these critical plains is the Dehgolan Plain, which is still facing a water shortage crisis despite its designation as a prohibited area. Therefore, in this research, the effect of tax and subsidy incentive policies for each added or saved cubic meter of water consumption on the changes in the cultivation pattern has been investigated in three scenarios of 10, 20, and 30 percent increase in the shadow price of water (714 Tomans) in 2023. The required data were collected by referring to Kurdistan Regional Water Company, Agricultural Jihad Organization, and the country's water demand system for seven major crops including Wheat, Barley, Forage corn, Potato, Cucumber, Alfalfa, and Rapeseed in Dehgolan plain. Then, the data were analyzed using the positive mathematical programming (PMP) model. The results showed that the application of tax and subsidy policies pushes the cropping pattern towards low-water-absorbing crops such as barley, wheat, and canola. It was also found that these policies reduce water consumption and gross farm yield. These findings show that the mentioned incentive policies can be an effective tool for managing water consumption in the agricultural sector. Of course, it is necessary to consider alternative solutions such as the use of new irrigation methods in addition to these policies to prevent negative effects on farmers' income.

The growing population and rising incomes have increased the water demand for agricultural, industrial and urban use.  On the other hand, water supply has shifted from surface sources to groundwater sources. This has significantly reduced the storage of groundwater resources. The growth of urbanization and the existence of two cities of Tehran and Karaj in the Tehran-Karaj plain has increased the demand for water in the domestic sector and as a result has reduced the share of water consumption in the agricultural sector. For optimal water management with considering the water demand in different economic sectors, in this study, the effects of changes in water demand in the domestic sector on agricultural activities, its economic value have been estimated.  The Stone-Geary Utility method was used to estimate urban water demand and the positive mathematical programming approach was used to estimate the economic value and effects of urban water demand on the agricultural sector. The results showed that the water economic value in the agricultural sector is equal to 550 Toman per cubic meter. Now, if the share of the agricultural sector in groundwater decreases by 1, 5, 10 and 20%, the economic value of water in the agricultural sector will increase to 600, 703, 761 and 976 Toman per cubic meter. Due to the constraints created by water demand in the domestic sector and the reduction of water availability, in addition to pricing based on the economic value of water in the agricultural sector, policymakers are proposing incentive policies to invest in modern irrigation systems in order to increase more water productivity

The aim of this study is to determine the optimal tariff for treated wastewater in the agricultural sector in the south of Tehran province. In order to achieve this goal, Used of positive mathematical programming (PMP) optimization method and the conditional valuation method (CVM) to estimate the conservation value. The required information was collected by completing 470 questionnaires by two-stage cluster sampling in the south of Tehran province in 2019. Based on the results, the cost price of treated wastewater was determined to be 21,523 Rial per cubic meter in Tehran province. Market price for each cubic meter of treated wastewater in Qarchak, Pishva, Rey and Varamin cities is 4444, 5556, 9778 and 5000 Rial respectively, value Marginal production is 10080, 15720, 17090 and 12370 Rial and willingness to pay of farmer 9474, 10136, 10173 and was determined to be 10671 Rial. Finally, by examining the conditions of market formation, the optimal tariff for treated wastewater in the south of Tehran province (PEWW) was determined to be 10,114 Rial per cubic meter. Due to the high cost price of each cubic meter of treated farmers are, it is suggested that the private sector enter the wastewater treatment market, because it can pay the difference between the cost price and the willingness to pay of farmers for the treated wastewater from government environmental assistance.

Water scarcity, improper management of water resources, excessive application of chemical inputs, and lack of proper cultivation patterns are present in agriculture. Lack of attention to these cases will inflict irreparable damage on the agricultural sector. Accordingly, attention to sustainable agriculture, conservation of water resources and prevention of improper use of chemical fertilizers are essential to reduce environmental pollution. In many cases, there is agreement on the river basin scale as a suitable spatial scale for analysis of water resources management. Tajan Basin with area of about 4187 km2 is one of the important parts of Caspian Sea Basin. The Current status of water resources in Tajan basin due to decrease in river runoff, has doubled the focus on the basin's water resources management.

In this study, with the help of positive mathematical planning and maximum entropy approach in GAMS, policies to reduce the use of chemical fertilizers and water in selecting the appropriate cultivation pattern for 2017 in the Tajan basin were reviewed. Within the model, the farmer maximizes the expected utility of their stochastic income, subject to resource and non-negativity constraints. To include both market and yields uncertainty, we calculated profit covariance matrices by using national averages for prices and yields for the 2018–2009 period. The resource constraints include land, water and fertilizer. Selected irrigated crops in the region include rice, wheat, rapeseed and corn. In the present study for simulating farmers' response, reduction scenarios including 5%, 10% and 15% of available water and fertilizer are considered. There are also two environmental sustainability index that are related to amount of the used fertilizer and water. The smaller the index is, the greater sustainability is provided in crop production.

Calibration of PMP pattern with maximum entropy approach showed that there is no difference between the value of target function, inputs and cultivation level in the current situation and calibration pattern. In all water reduction scenarios, the total cultivation area decreased. The results indicate that the agriculture in the basin is vulnerable due to changes in available water. The 15% decrease in water resources causes a significant decrease of 15/903% of the cultivation area. Cultivation area under fertilizer reduction scenarios has been lower in comparison with water scenarios, and so reduces the used fertilizer and increases soil conservation and water stock. In reduction scenarios of water and fertilizer, land reallocation is reduced due to less reduction in expected utility of farmers. In water scarcity conditions and lack of fertilizer, rice and wheat crops have higher economic benefits per hectare than other crops. The sustainability index for used fertilizer in all reduction scenarios of water and fertilizer is lower than the current pattern. Also the index of the used water in the PMP model is lower than the baseline in the region that decrease was 0.018%, 0.144% and 0.319% at three levels of 5%, 10% and 15%, respectively. In the scenario of 15% reduction of fertilizer, land allocation and economic benefits decreased by 13.83% and 0.034%, respectively. However used fertilizer and water index improved to 1.348% and 0.319%, respectively. Therefore, improving the water and fertilizer application index has a higher priority than reducing the expected utility in the region.

In the current cropping pattern, farmers do not pay attention to the environmental characteristics and sustainability of the region. While with the policies of reducing the quantity and price of chemical inputs and introducing different types of sustainability indicators, it is possible to develop a cultivation model. In addition to earning the necessary profit, it enables the optimal use of fertilizer and water inputs. Changing the behavior of farmers compared to the current pattern of input consumption requires strong motivation and reasons. Therefore, water quality tests and soil decomposition in the region, as well as providing appropriate formulas for optimal use of chemical fertilizers is needed. Extension services to increase people's awareness is a good solution for optimal use of inputs and increase the level of cultivation and farmers' profits.

The cotton as a strategic crop has the important role in creating job, foreign currency and increasing income in agricultural sector and related industries which has been considered by government. In the last couple of decades, the cotton cultivation area in Gorgan County which is one of the major cotton-producing regions has decreased considerably duo to high costs of production and continuation of import. Therefor the object of this study is mainly concentrate on assessing the influence of cultivation and profitability of cotton in Gorgan County influenced by government supportive policies using PMP. The data has been collected by filling out 295 questionnaires using the stratified random sampling method from farmers of Gorgan County in 2014-2015. Three cropping systems of cotton are considered in this study, including: mono-cropping, double cropping and intercropping systems and the governments supportive policies are measured in three parts such as cotton pricing policy, cotton production input subsidy policy and direct payment to cotton production policy. The result shows that the cotton production inputs subsidy has positive profitability among different government supportive policies, so that the most profitable one is related to the cotton mechanic harvesting policy with 1.78 percent of the change. According to results, it is recommended to increase cotton cultivation in Gorgan by applying production inputs subsidy.

Water supply and demand Management plays an important role in the agricultural sector. In recent years, due to inadequate management of agricultural water distribution, agricultural lands in Tajan Irrigation and Drainage Networks are suffering from excessive use of groundwater and salinity. Therefore, the purpose of this study was to investigate the sustainability of groundwater, water consumption, and distribution management in Tajan Irrigation and Drainage Network after implementing water-pricing policies and reducing available water of upstream lands. For this purpose, Positive Mathematical Programming model and the Asano sustainability index were used. The required data were collected from Agricultural Jihad Statistics, direct referral to Jihad-e-Agriculture Organization and Mazandaran Regional Water Company in years 2016 and 2017. The results showed that the situation of water resources in the region is not stable, while changing the cropping pattern and adopting different irrigation policies in the region will increase the sustainability of water resources from 0.45 to 0.27, which corresponds to changing from critical to good situation. The higher price policy for water up to 30% compared to the current conditions has little effect on irrigation water use. However, reducing available water of the upstream lands, in addition to reducing the amount of consumed water and managing its consumption, would improve the economic benefits of the network, with a minimum reduction in the upstream economic benefits. Therefore, in order to contribute to the sustainability of groundwater in the region, it is suggested that managers of the Tajan Network should adopt the policy of reducing available water to the upstream lands.

One of the most difficult duties for public decision-makers is to select a practical and legal instrument to receive water tariffs in the agricultural water pricing policies. This study aimed at analyzing the potential consequences of different instruments for irrigation water pricing (area, volumetric and two-part tariff) and their effects on the sustainability of irrigated lands with respect to economic, social and environmental impacts. For this purpose, farmers’ behavior in response to pricing instruments was simulated through positive mathematical programming and the composite indicators were calculated for sustainability measurement of different instruments in these irrigation water pricing policies using Analytic Hierarchical Process (AHP). The required data were collected in two-stage cluster sampling by 120 questionnaires completed from farmers under the irrigation network of Qazvin Plain in Iran as well as opinions and experiences of experts and documentary data. The results showed that the implementation of the studied irrigation water pricing policy instruments had negative impacts on economic sustainability indicator (i.e. profitability) and social sustainability indicator (i.e. employment) and a positive impact only on environmental sustainability indicators; and water consumption increased in area pricing and decreased in volumetric and two-part tariff pricing. In addition, the overall sustainability index in two-part tariff was higher than other water pricing instruments. Therefore, a two-part tariff pricing policy and adoption of alternative policies to achieve complete sustainability and compensate for the negative effects of this pricing policy were recommended.

Over recent years, unconventional extraction of irrigation water for producing agricultural products has decreased the level of groundwater in Dehgolan Plain of Kurdistan province in Iran, putting this vital resource at serious risk. This study aimed at investigating the effects of restrictive water supply policy on cropping patterns, farmers' incomes and the amount of water extraction from groundwater aquifer of Dehgolan Plain. For this purpose, a positive mathematical programming (PMP) model along with a maximum entropy (ME) model was developed and estimated. The required data was obtained in a two-stage cluster sampling method through completing 96 questionnaires from farmers in the villages of the region for the 2015-2016 farming year. The results showed that the irrigation water reduction policies had a great impact on the cultivation pattern and led farmers to products with more economic efficiency in water use. Furthermore, as a result of this policy, the gross margins in the first to third scenarios will decrease by 4.94, 9.96 and 14.94 percent, respectively, and the economic return on irrigation water will increase by 5.65, 12.64 and 21.63 percent, respectively. In conclusion, according to the results of this study, the strategy of restricting water supply along with the changes in cultivation pattern might effectively reduce water extraction and contribute to maintain and sustain the groundwater resources of the Dehgolan Plain.

Increasing competition, product diversity, and raising public awareness have driven consumer demand into fundamental changes. Thus, maintaining and expanding the current market require the discovery of demands and the satisfaction of customers through the creation of necessary changes in the production system, quality, marketing and sales of products. Therefore, this study aimed at ranking seven dairy companies through the elements of marketing mix, based on customer satisfaction in Tabriz County of Iran. For this purpose, a combined method of DEMATEL-ANP multi-criteria decision-making was used to prioritize the concerned companies. The results showed that "product" was the most important criterion in providing customers with relative satisfaction; and price, place and promotion criteria were in the next priorities. It was also concluded that Pegah Dairy Company was ranked the first in providing dairy consumer satisfaction. Dairy companies of Kaleh and Mihan were ranked the second and third respectively, and Ramak, Kohsaran, Sutich and Pak companies were ranked next in terms of satisfying the customers' satisfaction with dairy products.

Application of water resources management policies is necessary because of Water resources development constraint due to drought and climate change, poor management and such a water losses in agriculture. In the present study, different water resources management policies were analyzed by positive mathematical programming model and result of normative model was obtained and compared with result of positive model to compare different policies. The data were obtained by referring to the relevant departments of Qazvin province and also by 92 questionnaires of farmers during 1393-1394 year were selected by simple random sampling. The result of study showed that 10 percent reduction of available irrigation water for farms smaller than 25 hectares in Qazvin plain encourages farmers to properly manage of water resources.

Water valuation is one of the most important economic instruments for managing the increasing demand for water in agriculture. Hence, the main objective of this study is to estimate the economic value of water in greenhouse cultivation in Qazvin plain. To achieve the desired goals, the Positive Mathematical Programming (PMP) was used. In this research, the economic value of agricultural water was determined in the study area. Then, sensitivities such as changes in water resources inventories, increasing product prices, and lowering the production costs were analyzed and evaluated for the economic value of water. Data were collected for 2016-2017 agronomic year from greenhouse owners in a field survey questionnaire. After runing the model, the economic value of each cubic meter of agricultural water at the greenhouse level of Qazvin Plain was estimated to be 24730 Rials. Results showed that as the water supply decreases, the economic value of water will increase significantly. In addition, by applying the sensitivity of lowering the production costs and increasing the price of products, the economic value of water will increase. Therefore, considering the results of this research, more attention should be given to greenhouse crop production, in order to save water consumption and increase the irrigation efficiency.

The purpose of this study was to investigate the effects of different policies (water price increase, quotation and combination of these two policies) on economic, social and environmental criteria in cope with agricultural sustainability in Qorveh plain. Each of these policies was used at three levels of 10, 20 and 30 percent. A PMP model is used to simulate the effects of these scenarios. Then, the AHP method was used to calculating the weight of the indexes and sub-indicators, and in the final stage, using the TOPSIS approach, the scenarios were ranked and the best scenario was selected. The results of the study showed that all scenarios will reduce the total cropping area, gross profit and water consumption. Also, water pricing policy is not effective and only increased the farmers' costs, but the quotation and the combined polices are recommended as effective policies. Also, the environmental index was introduced as the most important decision indicator. Therefore, S7 scenario (10% in water price increase a with 10% water quotation) was identified as the best scenario to obtaining the sustainable goals in agriculture sector.ر

Mashhad plain is one of plains of Khorasan Razavi province, which is one of the prohibited and critical prohibited plains. Due to unlicensed and unauthorized exploitation, the groundwater level has been gradually lowered and with a deficit of reservoir. Therefore, choosing the right strategies to reduce water consumption in this plain is necessary. Various policies have been proposed to reduce agricultural water consumption by researchers, including the policy of expanding crops with low water requirements such as saffron. This policy may be a good solution to tackling the increasing use of water, but since different policies have different dimensions and effects, each policy must be explicitly examined for the impact of each policy, as well as the implications of each policy. In this regard, the consequences of the policy of extending the cultivation of saffron in three scenarios of allocating 5%, 10% and 15% of the total land area of the three counties located in Mashhad Plain was investigated using a positive mathematical programming model. The results showed that with the application of this policy, in all three cities, the income of farmers will increase, but water consumption will decrease only slightly in Binalud, and will not change in other two cities. Because with the expansion of saffron cultivation, instead of reducing the level of products with a high water requirement, the level of wheat and barley that requires less water than saffron is reduced, and therefore no reduction in water consumption. So, In the following, it was examined whether the policy would be to increase the cultivation of saffron, along with the absence of a decrease in total surface area of wheat and barley. It was observed that the application of this policy would reduce the consumption of water in all three cities and increase the income of farmers

The main problem of water resources management in the country, a balance between water supply and demand and to maintain this balance, the price or value of water is decisive role. The present study to determine the economic value of groundwater, for the long grain rice and long grain quality is high yielding. Information necessary to achieve the purpose of the survey of 205 rice farmers water their crops only for plain city water extracted from wells may have been collected in the crop year 1393-94. In determining the shadow price of water for the two varieties of rice in the way of positive mathematical programming (PMP), depending on the level of water available, farmers were divided into four groups studied and results showed that under scenarios of reduced 5 to 40 percent the amount of water, water prices respectively, in the first group (the most available water) and fourth (lowest available water) of 1810, 4370, 4770 and 4370 Rials was calculated to 3830 Rials is estimated at an average price of water is obtained

Excessive withdrawal of groundwater resources in the agricultural sector has led to an increase in cultivated land area and agricultural production, however, it has led to dropping of groundwater levels and drainage of aquifers. Consequently, most of Iran's plains are now considered as forbidden plains for underground water extraction. Therefore, proper policies for management of groundwater resources are essential. For this purpose, the present study aimed to evaluate the effects of economic policies of the agricultural sector on management of ground water resources in Kabodarahang Plain, by using a Positive Mathematical Programming (PMP) and Maximum Entropy (ME). The data and information was collected by referring to the relevant organizations and completing 141 questionnaires with multi-stage cluster sampling by farmers in 2016. The results showed that application of various senarios such as price increases, groundwater allocation , and combination of quotation scenarios simultaneously with increasing prices (combined) at levels of 10%, 20%, and 30% cause reduction in cropped area, decreased net profit of farmers, and reduced water consumption. Also, the results showed that the groundwater price increases scenario was not much effective and only increased the farmer's expenses, but the allocation/quotation polices and the combined policy are recommended as effective policies. Another result revealed that the quotation scenario, compared to the other scenarios, has higher economic returns per cubic meter of water consumption, thus it has been introduced as the best scenario in this research. Finally, it is suggested that the cropping pattern be directed towards products such as wheat and potato that have more gross profit for the water consumed and thus have more economic returns.

Farmers have always faced many risks such as price fluctuations in agricultural productions. Therefore, it seems important to identify the farmers risk aversion about price changes and consideration of it in the possible effects of price fluctuations on optimal cropping pattern. In this regard, this study examined the effects of crop price fluctuations on the reaction of sari farmers to the selection of suitable cropping pattern in 2012-2013 crop year using positive mathematical programming model. Data used including crops production costs in 2012-2013 crop year and crops price in 2002-2013 years were collected from Mazandaran Agriculture Organization. GAMS software has been used to analysis data. Results of decreasing 50% to increasing 50% in price fluctuations suggests that land use for riskier crops such as irrigated onions, dryland canola and irrigated potatoes reduce respectively about 17%, 4% and 2% in term of increasing 50% in price fluctuations, while cultivation of low-risk crops such as dryland soybean, dryland wheat and irrigated barley increase about 4%, 0.9% and 0.3%, respectively. According to study results, among the desired crops, cultivation of irrigated wheat has reduced in both increasing and decreasing prices fluctuation. On the other hand, reducing price fluctuations has no effect on rice and barley, while for other crops has observed adverse results to increasing price fluctuations. Such results can depend on the degree of risk aversion, the nature of the data and the ratio of risk to return. So, to deal the bad effects of price fluctuations should choose crops that have been minimal changes.

Iran with an average precipitation of 260 mm in a year is one of the [1]countries with limited water resources. For this reason, pricing policy can be used to manage water demand. However appropriate pricing of irrigation water in any region must be determined based on the condition and products of the region. For this purpose, the economic value of water and its effect on cropping pattern was determined in 10 scenarios. To this end, positive mathematical programming and maximum entropy method were applied. The required data for this study were collected through completion of questionnaires by a sample of 162 farmers in Dehgolan plain for cropping year of 2012. The results showed that extraction cost per cubic meter of water was 634.3 Rials and the difference between the extractions cost per cubic meter of irrigation water and its economic value was 1878.3 Rials. It is concluded that applying water pricing policy based of its economic value could lead to reduction of water consumption and also cultivated area of all crops.

In this study، we assessed the removing effect of chemical fertilizers subsidies on cropping pattern of agronomy in Shahre-Rey County. For this purpose، by simple random sampling method، 105 evaluation forms from Shahre-Rey County farmers between 2010 and 2011 were filled out، and Positive Mathematical Progamming model (PMP) with maximum entropy (ME) was used. According to cultivated area، farmers were divided into four homogenous groups، and the elimination effect of the chemical fertilizer subsidies through price changes in nitrate، potassium، and phosphate fertilizers was evaluated. The results indicated that the extent of planted areas in all crops was decreased in the first and second groups. In the third group، only the extent of planted areas of wheat and cauliflower was increased about 8. 569% and 6. 52%، respectively. Finally، in the fourth group، the extent of planted areas of barley was increased about 0. 818%. Also، the rate of using inputs was decreased and the planned output of all groups (1، 2، 3 and 4) was declined 4. 825%، 5. 402%، 8. 928%، and 1. 512%، respectively.

Harmful economic, environmental and financial impacts of fertilizer distribution through subsidies as well as its contradiction with regulations of WTO, it makes necessary to adopt a new policy. In this study, by combining Positive Mathematical Programming and Maximum Entropy technique, the impacts of cancellation of fertilizer subsidies and applying proposed direct payment policies on gross margin, output and input levels were simulated under four scenarios.Results show that replacing fertilizer subsidy with direct payment policy leads to decreasing of fertilizer use up to 17.38, 9.39 and 13.59 percent in first, second and third group of farmers, respectively. In view of the fact that results show the current policy of fertilizer subsidy isn’t efficient, applying a proposed direct payment policy is suggested to increase the economic and benefits environmental safety of fertilizer use.