Impact of water resources availability on agricultural sustainability in the Gavkhuni river basin, Iran

One of the most interesting water management case studies in Iran is the case of Zayandehrud River, the main river that supplies water to Isfahan Province which is located in Gavkhuni River Basin (GRB). This paper examines the present and future demands for water and determines the extent to which water will be available for agricultural use by the year 2020. Although demand and supply conditions in 2000 were more or less in balance, there was an increase in the supply of some 28% by 2010 due to the completion of the third trans-basin diversion and the development of other local water sources. However, the demand exceeded its supply in 2010 and the basin fell into severe deficit. In this condition, the only way to keep supply and demand in balance is to reduce allocations to agriculture. By 2020, agriculture would only have 5% more water than the present and water supply is only 90% that of the normal, and this would then shrink from 2025 onwards. In other words, agriculture would have to be sacrificed in order to ensure full supplies of water for the other sectors. The scenarios examined reveal that a sustainable agriculture can only be accomplished by water saving practices and management measures, which may further lead to reduced demand, control supplies, and improve the efficiency of water use

Effects of deficit irrigation on water productivity and maize yields in arid regions of Iran

Deficit irrigation in the Gavkhuni River Basin (GRB),Iran, is an effective method for alleviation of drought impacts on crop yields. Whilst it saves considerable amounts of water, it has little effect on crop yields. The effects of deficit irrigation on grain yield and yield components of maize were studied using two factors [namely, the variety at two levels (704 maize variety with 9354 kg ha -1 yield, and 647 maize variety with 8822 kg ha -1 yield) and irrigation at four levels (control, 100, 80, and 60% of water level use)] for three consecutive years. Significant differences (P≤0.05) were noticeable in grain yield, as well as depth and column of kernel among the irrigation treatments. In addition, the effects of cultivars on grain yield, 1000 kernel weight, number of kernel per ear row, number of kernel per column, and depth of kernels were insignificant. Nevertheless, the effects of irrigation treatments on 1000 kernel weight and number of kernel per ear row were not significant. Based on the results and considering the quantitative characteristics of the crop, it was established that for the deficit irrigating of maize, the 80% irrigation level (i.e. 80% of crop evapotranspiration) is the most advantageous treatment when water is not limited. However, when higher water productivity and the possibility of using the water saved are taken into consideration during severe drought conditions, 60% irrigation level treatment is recommended

Cropping pattern optimization for water resources allocation in Nekuabad irrigation network, Iran

During the last three decades in Iran, a high population growth rate had resulted in an increase in acreage and yield of summer crops with subsequent reduction in the fallow lands. Significant change occurred in the trend of cropping patterns towards crops with lesser water requirements from the limited water resources. Against this background a multi-criteria strategy is needed to improve the productivity of water and solve some major problems in the Nekuabad irrigation network located in the central part of Iran. The main aim of this study was to develop a multi-dimensional model that can optimize a cropping pattern not only to maximize the net benefit, agro-economic water productivity (net return to the volume of water used) and labor employment but also minimizing water consumption and total nitrate leaching. The ET0 calculator software which calculates ET0 using the long term weather data as input to the Penman-Monteith equation was used. Then, net crop water requirements were calculated with the AquaCrop model. The potential of the AquaCrop model in deficit irrigation practice for seven main crops in dry area of Nekuabad irrigation network were studied. A set of second-order, seasonal crop water production functions were developed using the multi-crop simulation model for each crop in the study area. Ultimately, allocations of cropped area and irrigation water were made at seasonal levels through non linear deterministic programming, considering economy, social and environmental aspects. In this way, four critical objective functions subjected to a number of constraints with the use of the general algebra modeling system program were proposed for optimal cropping pattern in dry, wet and normal climatic conditions. These functions were then applied to the predicted optimal cropping pattern and optimal allocated water. In the previous research using linear programming models, for each crop, fixed deficit irrigation ratio alternatives were imposed as input and the models compute optimal water and cropped area. In this study however, for each crop, crop water production functions ranging from 100 to 60% irrigation levels have been applied in the non linear programming model and the model computes the optimum irrigation volume ratio. The calibrated AquaCrop model performed well under full and water stress conditions to predict crop yields, biomass and canopy cover. The coefficient of determination of the regressed crop water production equation showed good correlation between applied water and yield for all the crops. After optimization of the cropping patterns, the highest agro-economic water productivity in the irrigation network was found for potato in the dry year, followed by potato, rice and silage maize. The highest magnitude of global agro-economic water productivity was for the dry season followed by normal season and wet season. The results show that an increase of 116.8 % in net income is attained according to the model for the entire Nekuabad network. A 19.8 % increase in labor employment in wet season was found as compared to the current situation. There was 11% decrease in nitrate leaching for dry season as compared to the current situation. The total optimal amount of applied irrigation water in the study area can be reduced by up to 16.3 % for dry periods. These results demonstrated considerable improvements for the entire Nekuabad compared to the current condition. Cropped area of rice with high water demand decreased as compared to current condition. In contrast, potato and silage maize areas with relatively low water requirement increased. This shows that the multi dimensional model developed in this study has successfully optimized the water allocation in the study area regarding economy, unemployment and pollution aspects

Diagnosis of Simulated External Root Resorption Using Conventional Intraoral Film Radiography, CCD, PSP, and CBCT: A Comparison Study

Background: Diagnosis of external root resorption (ERR) cavities may be challenging, especially when no clinical signs are seen. Therefore, the aim of this study was to compare the efficacy of conventional intraoral film radiography, charge-coupled device (CCD) detector, photostimulable phosphor plate (PSP) detector, and cone beam computed tomography (CBCT) for the detection of ERR. Methods: The study sample comprised 54 maxillary first premolars. Cavities were created by using a low-speed handpiece with round diamond burs of 1 mm in diameter. Digital and conventional radiographs were taken from each tooth. Three observers examined all images for the presence of resorption cavities. Data were statistically analyzed with the χ2 test. The reliability and degrees of agreement were also determined by the mean of Cohen's Kappa analysis. Results: The differences between the imaging methods in correct detection of root resorption for all sizes were not significant. For locations of root resorption, significant differences were found between CBCT and other methods in the apical regions. Conclusions: CBCT was only useful for detection of cavities located in the apical one-third of the root, compared to other digital or conventional methods

Water productivity, morphological and biochemical responses of Sorghum bicolor (L.) under various levels of drought stress

Sorghum is a potential fodder crop that has high yielding and superior quantity to feed of livestock. In arid and semi-arid areas, both quantity and quality are susceptible to drought. This study assesses the impact of drought stress on morphological characteristics, forage quantity and quality, and water productivity on two sorghum varieties. The experiment was carried out in a split-plot, based on the completely randomized design with three replications in Isfahan, Iran, in 2017, and 2018 crop years. The treatments consisted of irrigation treatments with three levels (control, 80, and 60% full irrigation) and two varieties of sorghum (Speedfeed and Pegah). The results showed that drought stress had no adverse effect on the vegetative traits and forage yield of sorghum, while it improved some traits related to animal nutrition. The results indicate that drought stress up to 60% full irrigation had no significant effect on the qualitative and quantitative yield of sorghum forage and water productivity. Besides,according to Stress Susceptibility Index and Stress Tolerance Index, Also increase wet and dry forage water productivity in 60% irrigation compared to 100%, the Pegah variety is more adapted to water stress conditions. The Speedfeed variety is appropriate as a result of animal nutrition, but depending on the reduction in Neutral detergent fiber and Lignin, the Pegah variety may be more appropriate for forage quality

Application of AquaCrop model in deficit irrigation management of winter wheat in arid region

Simulation models that clarify the effects of water on crop yield, are useful tools for improving farm-level water management and optimizing water use efficiency. The main purpose of deficit irrigation is high water productivity with less water supply to plants. In this research, the potential of AquaCrop model in deficit irrigation practice for winter wheat, the main agronomic crop in Gavkhuni river basin, Isfahan province, Iran, was studied. The results of reliability indices such as RMSE, d, E, CRM and deviation percent were 2.31 to 5.63, 0.97 to 1.00, 93 to 99, -0.15 to 0.016 and -0.70 to 12.00% respectively, and showed that, the model overestimated the simulated parameters compared with field data. This difference was more obvious in deficit irrigation treatments. The model provided excellent simulations of canopy cover, grain yield and water productivity. Considering only drought stress and neglecting other stresses such as salinity is the most important limitation of AquaCrop model. In this study, water productivity for the studied crop was in the range of 0.91 to 1.49 kg m-3 and its maximum value was in 40% deficit irrigation treatment. Asecond-order, yield-water function, obtained in this study is recommended for winter wheat crop. Also, the sensitivity analysis of AquaCrop model was carried out for winter wheat in this arid area in central Iran

Irrigated silage maize yield and water productivity response to deficit irrigation in an arid region

Simulation models have proven to be useful. The AquaCrop model, which has been expanded by FAO, simulates crop yield based on the applied water under conditions of full and deficit irrigation levels. In this study, the AquaCrop model's performance was tested using data for silage maize (Zea mays L.) under full (100% fulfillment of ETc) and deficit irrigation levels (90, 80, 70, and 60% of full irrigation) in the arid and semiarid environment of central Iran in the Gavkhuni River Basin (GRB). To calibrate this model, we used physiological measurement sets of cropping seasons 2000 to 2002. AquaCrop simulated well the decrease of the biomass yield (B-yield) of silage maize in response to drought as happened in the field. B-yield was decreased by 9.9% under deficit irrigation as compared to fully irrigated conditions. The coefficient of determination (R²) for simulation of B-yield and water productivity (WP) was 0.95 and 0.99, respectively. But the R²=0.77 was not satisfactory for actual evapotranspiration (ETa). The results for all investigated parameters in the three years showed that RMSE, d, ME, CRM, and E values ranged from 0.90% to 3.85%, 0.98 to 1, 1.25% to 6.4%, -0.027 to 0.03, and 0.817 to 100%, respectively. At the end, a local second-degree polynomial crop water production function (CWPF) for silage maize is presented.Hamidreza Salemi, Mohd Amin Mohd Soom, Sayed-Farhad Mousavi, Arman Ganji, Teang Shui Lee, Mohd Kamil Yusoff, Vahid Reza Verdinejadhttp://www.pjoes.com/abstracts/2011/Vol20/No05/list.htm