Akbar Alipoor; Kamran Davari; Mohammad Mousavi Baygi; Mahmoud Sabuhi; Aziz Izady
Abstract
Groundwater is the largest source of freshwater available on Earth, which has been threatened with extinction in many countries due to overdraft. Determining the optimal cropping pattern along with a reduction in water resources allocation that does not lead to a reduction in farmers' income can be an ...
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Groundwater is the largest source of freshwater available on Earth, which has been threatened with extinction in many countries due to overdraft. Determining the optimal cropping pattern along with a reduction in water resources allocation that does not lead to a reduction in farmers' income can be an appropriate strategy for groundwater sustainability. In the present study, a method has been proposed that, in addition to the sustainability of groundwater, minimizes farmers' loss of income. For this purpose, four groundwater use scenarios were first defined and groundwater level changes were calculated for each scenario using Neyshabur Decision Support System model. Also, economic productivity of water was estimated using a questionnaire for 242 agricultural wells and 9 dominant plants in Neyshabur plain, in 2016. To minimize farmers' income reduction, water was reallocated to different crops and the areas of cultivation were determined based on the ratio of economic productivity percentages of each crop. Due to changes in groundwater level and existing conditions, the scenario in which groundwater use was set equal to renewable water (414.9 M.m3) was selected as the best scenario. Implementation of this scenario would reduce the allocation of 227.5 M.m3 for groundwater sustainability. The results showed that the reduction of water allocation would result in a decrease of 27061 hectares of cultivated land area and a decrease of about 83.5 billion Tooman (local currency) in revenue. In order to compensate for the decrease in income, alternative crops of pistachio and saffron were suggested due to their higher economic efficiency and lower water consumption. In the proposed pattern, 18,000 hectares of saffron or 4473 hectares of pistachio replace the current crops that have the highest percentage of cultivated land in summer vegetables and sugar beet.
Masoud Mohammadi; K Davary; Bizhan Ghahraman
Abstract
Considering limitations of agricultural productions in arid and semi-arid regions, optimization of irrigation depth and leaching is very important. In this study, calibrated and validated AquaCrop model was used in order to optimize irrigation water depth and leaching for two varieties of winter wheat ...
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Considering limitations of agricultural productions in arid and semi-arid regions, optimization of irrigation depth and leaching is very important. In this study, calibrated and validated AquaCrop model was used in order to optimize irrigation water depth and leaching for two varieties of winter wheat (Ghods and Roshan) in Birjand region and one variety of wheat (spring Roshan) in Mashhad region. For winter wheat, irrigation treatments included 125%, 100%, 75% and 50% of water requirement and water salinities of 1.4, 4.5, and 9.6 dS/m for winter wheat. For spring wheat, irrigation treatments consisted of 100%, 90%, 65%, and 40% of water requirement and water salinities of 0.5, 0.9, 5.25, 8.6, and 10 dS/m. The coding written in Matlab program was linked to the AquaCrop in order to achieve the optimized values of irrigation and leaching in the land constraint conditions. The optimization results showed that net profit for the best irrigation and leaching management at all salinity levels and different wheat varieties, except for salinity levels of 8.6 and 10 dS/m in the spring Roshan variety and level of 9.6 dS/m in the winter Roshan variety, was more than the current management in field conditions. The increases in profits in optimal management compared to the current management for Ghods variety at the salinity levels of 1.4, 4.5, and 9.6 dS/m were 51.4%, 78.9%, and 142.5%, respectively. For the same salinity levels for Roshan variety, the increments were 42.7%, 20.8% and -0.3%, respectively. The increase in profits in optimal management compared to the current management for the spring Roshan variety at the salinity levels of 0.5, 0.9, 5.25, 8.6 and 10 dS/m, were 5%, 13.2%, 34.3%, -27.7%, and -51.4%, respectively. In general, the results show that in the regions where drainage problem due to irrigation water is an important environmental problem and causes dissatisfaction among the downstream farmers, applying less water and accepting negligible decrease in the benefits (minimum 0 and maximum 29%) could resolve the problem.
Masoud Mohammadi; Bijan Ghahreman; Kamran Davari; Majid Vazifehdoost; Hamideh Noori
Abstract
Field studies to determine optimum amount of water required for maximum production are time-consuming and expensive. Therefore, in this study the agro-hydrological model SWAP 3.03 was used to simulate winter wheat yield under different qualities and quantities of irrigation water and to determine water-salinity-yield ...
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Field studies to determine optimum amount of water required for maximum production are time-consuming and expensive. Therefore, in this study the agro-hydrological model SWAP 3.03 was used to simulate winter wheat yield under different qualities and quantities of irrigation water and to determine water-salinity-yield optimum function. Irrigation treatments consisted of four water salinity levels (S1=0.7, S2=2, S3=4 and S4=6 dS/m), three amounts of water (W1=80, W2=100, and W3=120 mm), and six levels of management allowed depletion (MAD1=0.3, MAD2= 0.4, MAD3= 0.5, MAD4= 0.6, MAD5= 0.7 and MAD6= 0.8). Yield and water use efficiency values were determined in different modes and the best MAD value obtained was 0.5. Yield data were fitted to different forms of production functions (simple linear, logarithmic linear, quadratic and transcendental) and the best one was established based on sensitivity analysis. The maximum grain yield (6619 kg/ha) corresponded to W1S1MAD2 treatment and the minimum yield (2048 kg/ha) corresponded to W1S4 MAD3 treatment. The results showed that the quadratic production function was optimal for production and could be recommended. Investigation of the maximum values of error (ME) showed that the logarithmic linear and simple linear functions had the highest error. In the irrigation treatments, W1S1MAD3 and W1S1MAD4 with 0.61 kg /m3 had the highest water use efficiency. However, water use efficiency decreased when water stress and salinity increased. The iso-yield curve showed that by increasing amounts of irrigation, more saline water could be applied without a change in yield.