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mohammad amin khandan barani; Peyman Afrasiab; mehdi akbari; Masoomeh Delbari
Abstract
In this research, the status of water productivity for wheat production and strategies to increase water productivity in different quantitative conditions of water was determined and analyzed in the irrigation district of Sistan Dam. In this regard, the SWAP simulation model was calibrated and validated ...
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In this research, the status of water productivity for wheat production and strategies to increase water productivity in different quantitative conditions of water was determined and analyzed in the irrigation district of Sistan Dam. In this regard, the SWAP simulation model was calibrated and validated by considering the current water resources operation, various quantities of irrigation water, and use of field information. Water production functions were used to determine the irrigation schedule (time and depth) for wheat crop. The results of field measurements in the crop year 2016-2017 in the irrigation district showed that farmers irrigate wheat on average four times in the current conditions. Farmers' average crop yield and water productivity were about 1450 kg/ha and 0.41 kg/m3, respectively. These results show that available water is not appropriately used and should be addressed with practical solutions to improve water productivity. The validation and calibration results of the SWAP model also showed the high accuracy of the model in the case study. The results of different management scenarios of eliminating some irrigation shifts compared to the existing conditions indicated that, although there was no significant difference in water productivity, crop yield decreases about 37%. The results of evaluating the scenarios of reducing the depth and frequency of irrigation (using 640 mm per season and applying 40 mm at each shift) showed that, with reliable and timely water supply and more frequent irrigation, water productivity could be increased by 30% compared to the baseline scenario; and crop yield can be doubled. In these scenarios, the presence of adequate moisture in the plant's root zone increases the yield, and the amount of deep percolation is greatly reduced. The amount of water used by farmers is excessive for various reasons. Therefore, it is recommended to train farmers on how to improve irrigation and crop management according to the water available in the irrigation district, so that they can distribute water according to the real needs of the plant and irrigate at the right time and sufficient quantity.
Mohammad Hassanli; Peyman Afrasiab; Mahmoud Sabuhi; Hamed Ebrahimian
Abstract
The economic value of water is one of the most important factors for allocating water among various consumptions and encouraging users to take necessary actions to increase investments related to improving water productivity. There are several methods for economic valuation of water. In this study, due ...
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The economic value of water is one of the most important factors for allocating water among various consumptions and encouraging users to take necessary actions to increase investments related to improving water productivity. There are several methods for economic valuation of water. In this study, due to the key role of water in irrigation of agricultural products, residual valuation method was used for agricultural wells in Varamin County, with a wide range of water salinity. The average economic values of water for cucurbits, wheat, barley, and alfalfa were 2513.1, 5334.5, 1933.0 and 5647.6 Iranian Rials per cubic meters (IRR.m-3), respectively. The exchange price of water among the farmers in the study area was calculated as 5231.8 IRR.m-3, which was close to the calculated residual value for wheat and alfalfa crops. The coefficient of determination (R2) for the relationship of economic value and salinity of irrigation water for the above crops was 0.806, 0.878, 0.865 and 0.702, respectively, which indicates that the main changes of economic value of water is related to salinity of water. According to the relationship between salinity and irrigation water value in the study area, the residual value of water was zero in the electrical conductivity of 3.61, 7.30, 6.05, and 8.24 dS.m-1 for cucurbits, wheat, barley, and alfalfa, respectively. As a result, the water pricing policy in the study area should be such that for water salinities higher than the mentioned values, the selling price of water is set lower than the current value, so that the farmers do not suffer losses. Another option is that choice of crop should be based on greater resistance to salinity and its economic value.
H J; P A; M D; M T
Abstract
Evapotranspiration of orchard crops is often determined by indirect method and based on meteorological data due to the difficulties inherent in direct measurement instruments such as installation of large lysimeters or precision equipment, and long growing seasons of tree crops. Evapotranspiration estimation ...
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Evapotranspiration of orchard crops is often determined by indirect method and based on meteorological data due to the difficulties inherent in direct measurement instruments such as installation of large lysimeters or precision equipment, and long growing seasons of tree crops. Evapotranspiration estimation with sufficient accuracy is not feasible due to spatial variability of meteorological parameters and, sometimes, due to inappropriate distribution of meteorological stations. Therefore, using methods based on remote sensing, which account for these variations, is much more desirable. In this research, evapotranspiration of olive trees at different phonologic stages was measured using direct and indirect methods in Tarom district of Zanjan Province. In the direct method, actual evapotranspiration was determined by measuring moisture balance components, whilst in the indirect one, it was specified with the help of satellite imagery, the SEBAL algorithms, and Penman-Monteith equation. Olive crop coefficient was subsequently calculated and evaluated by determining reference crop evapotranspiration. The results indicated that evapotranspiration calculated by the remote sensing method at different stages of the growth had acceptable conformity with soil moisture balance data and evapotranspiration values obtained from the Penman–Monteith equation (the respective correlation coefficients were 0.95 and 0.88) and both evapotranspiration curves along the growing season had a similar increasing and decreasing trend. Moreover, crop coefficient obtained by the SEBAL algorithm and the water balance methods were well correlated (R2=0.86) and the remote sensing method with the aforementioned advantages can be used in predicting evapotranspiration.
m a; p a; m y; a l; m d
Abstract
A second crop in paddy fields has economic advantages resulting from the production of crops (canola, beans, garlic, triticale, soybean, etc.), Preparation of rice bed for mechanized harvesting, strengthening the economy of farmers’ families, increase the incentive for farmers to stay in the village, ...
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A second crop in paddy fields has economic advantages resulting from the production of crops (canola, beans, garlic, triticale, soybean, etc.), Preparation of rice bed for mechanized harvesting, strengthening the economy of farmers’ families, increase the incentive for farmers to stay in the village, etc. Due to the inability of the existing surface drainage systems in rapid depletion of water from the root zone, conditions for planting a second crop in paddy fields is not suitable. This can be provided by installing subsurface drainage systems, which, in addition to creating more favorable conditions for planting and harvesting rice, allows cultivation of other crops in the wet season. This research was conducted to determine the appropriate space and depth of subsurface drainage in paddy fields in order to provide favorable conditions for planting a second crop. The experiment was laid out in one and a half hectares of paddy fields at Rice Research Institute of Iran in Guilan province, in 2014. Drainage treatments included: six conventional subsurface drainage systems with rice husk envelope including drainage system with different drain depth and spacing L7.5 D0.8, L10 D0.8, and L15 D0.8, L7.5 D1, L10 D1, and L15 D1, surface drainage, and the control (without drainage). All lines were 40 meters long and made of PVC corrugated pipes with a diameter of 125 mm. Rice husk was used as a covering around the pipe drain. The results showed that subsurface drainage spacing of 15 m had failed to lower the water table depth to an acceptable level and provided the conditions only for the cultivation of shallow-rooted plants such as dill, parsley, and leeks. Also, surface drainage could reduce the excess water in the soil by 22% compared to control. To provide suitable conditions for the cultivation of second crops such as canola and beans, subsurface drainage spacing of 7.5 and 10 m seemed effective. However, to avoid excessive drainages by 7.5 m spacing, subsurface drainage spacing of 10 m was selected as the best space at drainages stage, for a second crop. Furthermore, due to the lack of significant differences in water table depth between treatments L10D1 and L10D0.8,theywere identified as suitable drainage systems at 0.8 m depth.