مجله پژوهش آب در کشاورزی
سال سی و چهارم شماره 2 (تابستان 1399)

Presently, the main challenge of agricultural sector is improvement of crop water productivity (CWP). To evaluate the effect of water stress and planting date on grain yield, water productivity and yield components of wheat (Pishgam var.), an experiment was conducted as split plot based on complete randomized design with three replications, at Kashmar Agricultural Research Station, in 2018-2019. Irrigation treatments included 100% of irrigation water requirement (IWR), 80% IWR, 60% IWR, and 40% IWR as the main treatments, and three planting dates including 23rd September, 23rd October and 23rd November as sub treatments. The results showed that water stress had significant effect on grain yield, water use efficiency (WUE), and harvest index (HI) at 1% probability level, such that with increasing water stress, the grain yield, HI and WUE was decreased. Also, the results showed that the effect of sowing date on grain yield, thousand kernel weight, and number of kernels per panicle, HI, and WUE was significant. The highest values of grain yield, HI, and WUE were 7227.33 kg/ha, 32.77 %, and 2.51 kg/m3, respectively, and belonged to 23rd October and 100% IWR treatment. The lowest of these values were 2000 kg/ha, 15.3%, and 1.14 kg/m3, respectively, related to 23rd November and 40% IWR treatment. The interaction between water stress and planting date had significant effect on all agronomic traits, except the number of kernels per panicle and WUE. According to the results of this study, irrigation treatment of 100% IWR and planting date of 23rd October can be considered for autumn wheat cultivar (Pishgam var.) in arid and semi-arid region of Kashmar.

Agriculture is one of the most important economic sectors of Iran and the largest consumer of surface and underground water resources. Since various risks threaten agricultural water supply systems, developing a risk analysis framework is inevitable in order to identify and assess the impact of the aforementioned systems on promoting sustainable agricultural development. Therefore, for the first time, the present study has attempted to develop a drought risk analysis model for agricultural water supply system with the Bayesian network. The structure of this model, which consists of nodes and their interactions, is designed by using river discharge, water released from the upstream water diversion system, groundwater and irrigation network demand to provide system risk. In order to investigate the capability of the developed model, the risk analysis of the modern Roodasht Irrigation System in Isfahan was investigated. The risk values of the Roodasht agricultural water supply system were estimated in the range of zero to 58.11% and an average of 39.82%. The results showed that this model has good accuracy and performance in both training and test sections, with the root mean squares error of 0.09 and 0.1, coefficient of determination of 0.85 and 0.75, and overall index of model performance of 0.82 and 0.74. The results of this research and the proposed model helps operators and decision makers to better plan the allocation of irrigation water based on the risks predicted in hydrological drought conditions.

This study aimed to investigate the effect of subsurface drip irrigation on leaf area index, root distribution, quality and yield of sugarcane for the first ratoon. For this purpose, a field with subsurface drip irrigation management was studied. Three measurement stations were selected in the field. The amount of water consumed for this field in 2017- 18, was 19531 mm. During this period, 117 mm of rainfall also occurred. Number of plants, number of green leaves, leaf length and width over one meter of plants row were counted and measured six times at 91, 99, 105, 112, 119 and 128 days after harvesting of plant. Number, length and width of leaves averaged 7.2, 101 cm and 2.9 cm respectively. The LAI value was affected by the number of plants. Weight of 20 stalks, brix, POL, purity (PTY), Quality Ratio (Q.R), brown sugar yield (Y) and white sugar yield (SY) in subsurface drip irrigation were 15.8 kg, 22.2%, 19.8%, 89.1%, 6.7, 21.3 ton/ha and 14.9 ton/ha respectively. Also different root characteristics were measured. Root weight, length, area, volume and diameter were 79.5 g, 707.55 cm, 793.3 cm2, 70.8 ml and 1.05 mm, respectively. Shoot/ root ratio was 5.73 g / g. Finally, in deeper and lower layers of soil, the root diameter is 20% more than the surface layer.

Water resource deficiency and the necessity of sustainable production in irrigated lands have attracted much attention to water productivity issues. In this regard, analysis, estimation, and preparation of water productivity map are necessary as an influential factor to recognize cultivation potential in irrigated lands. The aim of this study was to select a proper interpolation method for water productivity and investigate spatial changes in water productivity in Iranian wheat production centers. In this research, 241 field data were used, of which range of water productivity (irrigation water + effective precipitation) was estimated between 0.3 to 2.58 kg.m-3 with the average of 0.79 kg m-3, in 2016-2017 season. Interpolation methods used included Ordinary Kriging, Inverse Distance Method (IDW), and Radial Basis Function (RBF). Cross Validation technic was applied to evaluate methods by statistical measures such as Root Mean Square Error (RMSE), Mean Bias Error (MBE), and Mean Absolute Relative Error (MARE). Interpolation methods evaluation showed that between available procedures, typical Kriging method with exponential semi-variogram model had the most proper condition to prepare wheat water productivity zoning map. The results of the spatial analysis of water productivity confirmed that geostatistics could be used with acceptable accuracy (MBE=0.005) to provide water productivity mapping. Results of Cluster analysis of the effective factors (salinity of irrigation water, soil salinity, and crop cultivar) on wheat water productivity index showed that the areas suitable for wheat cultivation were separated into 13 independent groups (at the 5 percent level), such that the highest and lowest mean water productivity of wheat were observed in group 5 (Mean = 0.84 kg.m-3) and group 10 (Mean = 0.41 kg.m-3), respectively.

Irrigation water scarcity is one of the major limiting factors in agricultural production. This study was conducted to investigate the effect of different intensities of water deficit stress on yield and water use efficiency of Chamran 2 wheat cultivar in a moderate-textured soil in Khuzestan province. In this research, 10 treatments including full irrigation and water deficit stress at three intensity levels (low, moderate, and severe) were applied under two conditions: during whole growing season or at a given stage of plant growth. This research was done as a completely randomized design with three replications. The salinity of studied soil was 2.95 dS m-1, and soil texture was silty clay loam. The mean water use in different stress treatments was less than full irrigation by 17% (moderate-intensity stress in the third growth stage of wheat) to 43% (high-intensity stress throughout the plant growth period). Applying different intensities of water stress caused reduction in wheat grain yield by 13% (low-intensity stress throughout the growth period) to 76% (high-intensity stress throughout the growth period). The results showed that water stress at stem elongation and grain filling stages of wheat reduced the grain yield more than stress at flowering and milk stages. The lowest value of mean thousand kernel weight (28 g) was observed in the treatments applied in the final growth stage of wheat, confirming the importance of irrigation effects during grain filling stage on the quality of grain. The overall water use efficiency in low-intensity water stress (0.78 g L-1) was higher than the full irrigation treatment (0.62 g L-1), probably due to the reduction of irrigation water losses by drainage and evaporation.

In order to investigate the effect of soil amendments, zeolite and superabsorbent polymer, on the quantity and quality of sesame yield under drought stress, a factorial experiment was performed in randomized complete block design with three replications, at Research Field of College of Agriculture, University of Birjand, in 2017-2018. Treatments included irrigation at two levels of 50% and 100% water requirement and amendment materials at 6 levels of Z0, Z1, Z2, Z3, Z4 and Z5. (Z0= Control, Z1=adsorbent polymer (125 kg / ha), Z2 = 11.2 ton/ hect of zeolite and Z3 =6.2 ton/hect of zeolite, Z4= zeolite 11.2 ton / hect of zeolite + 125 kg / hect of adsorbent polymer, Z5 =6.2 ton/ hect of zeolite + 125 kg /hect/ of adsorbent polymer) In this study, 1000-grain weight, percentage of crude grain oil, crude protein of grain, plant height, grain yield, harvest index, and water use efficiency were investigated. The results showed that 1000-grain weight, oil percentage, grain protein, plant height, and sesame grain yield were affected by different levels of irrigation and amendments at 1% probability level. Also, harvest index and water use efficiency were affected by different levels of amendments at 1% probability level. Oil percentage, grain yield and harvest index were affected by interaction effects of irrigation levels and amendments at 1% probability level. The highest grain weight, percentage of crude grain oil, crude protein of grain, plant height, grain yield, harvest index, and water use efficiency were observed in Z4 treatment. The results showed that the change in irrigation level from 100% to 50% significantly reduced yield. The highest amount of 1000-grain weight in different levels of amendments was 4.12 g in Z4 and the lowest was 2.89 g. in Z0 treatments Also, the highest amount of crude grain oil in irrigation and different levels of amendments was 56.8% and 40.5%, respectively. The highest and the lowest amount of crude protein in response to different levels of amendments were 15.7% and 13.1%, respectively. The results showed that drought stress had a negative effect on plant growth, but the use of zeolite and superabsorbent polymer partially offset this effect.

In order to investigate the effect of salinity stress on applied water, yield and water use efficiency of Damask rose, an experiment was conducted based on completely randomized design with three replications and four levels of water salinity including 2.8, 5, 8 and 11 dS.m-1 at Research Greenhouse of National Salinity Research Center, during 10 Oct 2018 to 30 Sep 2019. In this study, volume of applied water and drainage water, evapotranspiration, flower yield, essential oil yield, and water use efficiency (based on flower yield) were determined. The results showed that the average of applied water, evapotranspiration and drainage water in each irrigation were 14.3, 8.4 and 5.9 L per plant for all treatments, respectively. Also, sum of applied water, evapotranspiration and drainage water volume during the experiment were equal to 616, 363 and 253 L per plant, respectively. The sum of irrigation water volume was 619, 625, 610 and 610 L per plant in 2.8, 5, 8 and 11 dS.m-1 treatments, respectively. Flower yield in 2.8, 5 and 8 dS.m-1 treatments were 60.3, 55.8 and 57.1 g/plant and had no significant difference, such that plants treated with 5 and 8 dS.m-1 had a decrease of 7.46% and 5.25% compared to the 2.8 dS.m-1 treatment, respectively. However, treatment of 11 dS.m-1 had the lowest flower yield (22.66 g/plant) with a decrease of 62.42% compared to the treatment 2.8 dS.m-1. The results showed that the highest water use efficiency of Damask rose was obtained in treatments 2.8, 5, and 8 dS.m-1 (0.09, 0.08 and 0.09 kg/m3) and the lowest (0.03 kg/m3) was in salinity of 11 dS.m-1. Salinity stress levels of 8 and 11 dS/m caused the highest percentage of essential oil (0.025% and 0.027%, respectively) and salinity of 2.8 and 5 dS/m caused the lowest percentage of essential oil (0.022% and 0.021%, respectively).

Sustainability of water resources has the most important role in the sustainability of agricultural systems. In this study,  positive mathematical programming was applied in 2018-19 to evaluate the sustainability of water resources and to determine the cropping pattern in Golestan province based on water demand management policies, i.e. water price increase by 50% and 100%, and reducing water quota by 10% and 20%. First, according to water price increases and water quota policy scenarios, the cropping pattern was evaluated in this area. Then, by using the sustainability indicators such as gross margin (GM), water consumption, economic efficiency, and labor efficiency the sustainability of water resources was calculated. Based on water price increases by 50% and 100%, water consumption and GM decrease by, respectively, (2.72% and 5.44%) and (5.06% and 9.99%). Also, based on water quota policy of 10% and 20% reduction, water consumption and GM decrease by, respectively, (8.9% and 11.56%) and (0.54% and 1.75%). In addition, GM per unit of water in agricultural sector decreases by 2.41% and 4.81% in response to to water price increase by 50% and 100%, respectively, and in case of 10% and 20% reductiion in water quota policy, it increases by, respectively, 9.17% and 11.09%. Water price increase by 50% and 100% and water quota reduction by 10% and 20%, increase water labor efficiency by, respectively, (0.78% and 1.6%) and (2.6% and 5.8%). Based on the result, if the government is going to increase water sustainability by using demand management policies, the water quota policy is more efficient. Also, the government should support farmers by direct payments to compensate for their lost profits.It is also recommended that irrigation methods with high efficiency be employed.

Nowadays, participatory water management receives much attention as one of the key elements of sustainable water resources management. The feasibility of good governance in the process of participation of stakeholders in water exploitation can meet the interests of all users in a fair way. The purpose of this research was to investigate the feasibility of good governance in the process of participatory water management. The study was conducted in Payvand Production Cooperative (PPC), Aqqala County. Research method was survey and questionnaire tool was used for collecting the required data. Target population included 400 farmers who were members of PPC and received services related to participatory water management. The data was collected from 196 farmers from 7 targeted villages. Reliability of research questionnaire was approved based on opinion of experts, and its validity was confirmed by Cronbach`s Alpha coefficient in two parts: importance and feasibility of good governance components. Results of evaluating the feasibly of good governance components showed that the majority of respondents believed that the components of good governance in the process of participatory water management in the study area had been considered at an acceptable level. Also, the results of one sample t-test showed that the process of participatory water management in the study area was successful in terms of attention to all five components of good governance, namely, public participation and collective agreement, responsibility and law enforcement, accountability and transparency, fairness and efficiency and effectiveness. Results of independent sample t-test indicated that respondents whose main job was farming (compared to those whose main job was not agriculture) and respondents who received water share in a group manner (compared to those who received water individually) evaluated the feasibility of good governance components at high level.

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, 1424.6 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, 0.932, 0.911, 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, 5.20, 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.