مجله پژوهش آب در کشاورزی
سال سی و سوم شماره 3 (پاییز 1398)

In this study, six irrigation treatments including well water (1.23 dS.m-1; control treatment), saline water (15 dS.m-1), alternate saline water and freshwater, mixture of 50:50 saline and freshwater (7.2 dS.m-1), subsurface irrigation with saline water (15 dS.m-1), and subsurface irrigation with well water (1.23 dS.m-1) were evaluated on some growth parameters, yield, and biochemical characteristics of Quinoa (CV. Titicaca). The research was done based on completely randomized design including 3 replications as pot planting in the Ferdowsi University of Mashhad, in greenhouse conditions, during 2017-2018. The results showed that the effect of different irrigation regimes on total soluble carbohydrate in leaf and stem, root fresh weight, and root length was significant at 1 percent level (P<0.01), while the leaf and stem fresh weight were significant at 5 percent level (P<0.05). Subsurface irrigation with saline water decreased leaf, stem, root fresh weight; grain yield, 1000 kernel weights, total soluble carbohydrate in leaf and stem by about 14%, 12.1%, 47.9%, 6.5%, and 5.6 %, respectively. Also, total soluble carbohydrate in leaf and stem increased by about 55.3% and 70.09 %, respectively. The alternate irrigation treatment decreased leaf, stem, root fresh weight, grain yield, and 1000 kernel weight by 22.8%, 23.7%, 34.1%, 8.1%, and 7.7%, respectively. Irrigation with saline water (15 dS.m-1) during all of the growth stages decreased grain yield and 1000 kernel weights by 20.8% and 20.0 %, respectively. In this research, sub-surface irrigation treatment with freshwater was the optimum treatment with the highest yield. Thus, if saline water is used, alternate irrigation treatment is recommended.

Some experiments were performed around the Agricultural and Natural Resources Research Station of Islamabad-Gharb in order to determine The effect of surge irrigation on yield of water productivity(WP) and water use efficiency of maize in that area. The statistical design of the research was randomized complete block with 4 treatments in 3 replication, as a composite analysis in two years (2015 and 2016). The treatments were continuous irrigation method (c), surge irrigation method with 1 to 1 on and off flow ratio (S1-1), surge irrigation method with 1 to 2 on and off flow ratio (S1-2), surge irrigation method with 1 to 3 on and off flow ratio (S1-3).  Corn variety SC704 was used for planting. The results showed that in 2015 and 2016, savings in the consumption of water compared to continuous irrigation was respectively, 10.8% and 10.4% in S1-1 treatment. 10.4% and 10.5% in S1-2 and (S1-3) treatment, respectively 11% and 10.5%. Combined analysis of variance (ANOVA) showed that performance parameters had no significant difference between treatments during different years. The results indicated that the water productivity values for total yield and grain yield were higher in surge irrigation treatment than in the continuous irrigation. WP based on total corn ear weight was 0.69 kg/m3 and based on grain weight, it was 0.54 kg/m3. These values represent 0.07 and 0.06 kg/m3 higher WP compared to continuous irrigation. The average water use efficiency was 32.3% for continuous irrigation and it was 36% for surge irrigation which was 3.7% more than continuous irrigation. Generally, the results showed that surge irrigation with a cycle ratio of 1 to 2 was more suitable for irrigation.

In order to study yield and water productivity of wheat in common cropping rotation (wheat-sugar beet) in cold regions, a research was conducted in Jolge-Rokh Research Station, Khorasan Razavi Province, Iran. The experiment used split-split plots in randomized complete block design (RCBD), with three replications, and was conducted during 2013-2016. Treatments were tillage methods (conventional tillage, minimum tollage, and no tillage) in the main plots, residue management (no residue, and leaving 30% and 60% residue) in sub-plots, and irrigation water levels (50%, 75% and 100%) in sub-sub plots. Results of analysis of variance showed that various tillage methods and residue management had no significant effect on yield and water productivity, but effect of irrigation water levels was significant (P<0.01). Yield in 75% and 100% water treatments was 4751 and 4961 kg/ha, respectively, with no significant difference. However, yield at 50% water consumption was about 3574 kg/ha, which was significantly lower than the other treatments. Water productivity in 50%, 75% and 100% water use was 1.067, 0.960, and 0.875 kg/m3, respectively. The highest wheat yield (6331 kg/ha) was obtained from minimum tollage with 30% residue and 100% of water level. The highest water productivity of wheat (1.173 kg/m3) was obtained in no-tillage, 30 present residue, and 75% of water use. Water productivity of no tillage treatment+60% residue and 50% water use, and conventional tillage treatment+ no residue and 50% water use were in the second and third place with values of 1.136 and 1.132 kg/m3, respectively.

Water scarcity is one of the most important environmental factors limiting crop production. Consumption of natural fertilizers can make optimal use of water in irrigation. The aim of this study was to investigate the effect of deficit irrigation and humic acid on yield and water use efficiency in common bean. The experiment was conducted in split plots based on randomized complete block design, with three replications in Guilan province, in 2016. The main factor was irrigation at three levels (rainfed, 50%, and 100% water requirement) and the sub factor included humic acid spraying at four levels (0, 2, 4, and 6 L.ha-1). In irrigation treatments, highest average seed yield (2610 kg.ha-1) was obtained in full irrigation conditions (100% water requirement). In the humic acid spraying applications, maximum seed yield was observed at 6 L.ha-1 with average of 2661 kg.ha-1. In interaction of irrigation and humic acid, the highest seed yield was obtained in full irrigation and 6 L ha-1 humic acid with an average of 3547 kg.ha-1. The highest seed yield (3030 kg.ha-1) was obtained in 50% water requirement and 6 L.ha-1 humic acid. The highest seed yield in rainfed conditions was obtained at 4 and 6 L.ha-1 of humic acid, with an average of 1461 and 1406 kg.ha-1, respectively. In different irrigation treatments, the highest water use efficiency was obtained with the mean of 1.78 kg.m-3 in rainfed treatment. The humic acid treatments had a positive effect on water use efficiency in comparison with the non-humic acid treatments, but there was no significant difference between treatments 2, 4, and 6 L.ha-1. Altogether, the results of this study indicate the beneficial effects of humic acid on water deficit stress in common bean cultivation in the study area.

To ensure optimal operation of the drip irrigation system, it should be evaluated periodically. This research was conducted to evaluate the technical and hydraulic performance of subsurface drip irrigation system in sugar cane plantation in Sugar Cane Research and Training Institute of Khuzestan during growing seasons of 2016-2017 and 2017-2018. For this study, four laterals were selected in experimental field (the first, one third, two third and the last laterals) and four sections including the first, one third, two thirds, and the last were determined on each laterals. Then, the volume of effluent water was measured for three minutes at any measurement point and the system parameters were calculated. Results of the evaluation of the drippers in the laboratory showed that the manufacture's coefficient variations (Cv), coefficient of uniformity (Cu), and distribution uniformity (Eu), coefficients were 15%, 90%, and 84 percent and the values of the exponent x and the k coefficient in the discharge-pressure equation were, respectively, -0.043 and 2.41. Means of Cu, Eu, coefficient of flow variations (Vqs), and Uqs during two growing seasons were 89.2%, 87.8%, 10.3%, and 89.7 percent, respectively. Based on these results, system performance was generally good. Also, by measuring pressure at different points of the system in the middle of the second growing season, the ASAE assessment indicators including: Vqs, Uqs,Vhs, and Vpf were 9%, 91%, 25%, and 13 percent, respectively. Thus, in terms of the overall performance of the drippers and uniformity of distribution the studied irrigation system was considered to be relatively good to good.

One of the most important design factors in using subsurface drip irrigation method is determining the moisture distribution for the soil texture and the characteristics of drippers. In this study, the distribution of moisture and salinity in a heavy textured soil (silty-clay) was investigated under subsurface drip irrigation of a sugar can plantation. The results were used to determine the best installation depth for drip pipe and distance of drippers on it in two-row cane crop cultivation. The experiments were carried out at a discharge rate of 1.2 liters per hour, three depths of drip pipe (15, 20, 30 cm), and two drippers spacing (50 and 60 cm), in three replicates. The soil moisture content was between the field capacity and the permanent wilting point, with maximum moisture advance of 60 cm horizontal and 90 cm vertical from drip pipe in all treatments. During the investigation period, soil salinity in the 0-30 cm layer was increasing, while at depths of 30-60 cm and 60-90 cm, a decreasing rate was observed. Generally, soil salinity increased with distance from drip pipe. The highest soil salinity in the different (13 dS/m) treatments was related to dripper spacing of 50 cm and at a point with a horizontal distance of 60 cm from the drip pipe at a depth of 15 cm. Also, to estimate the amount of soil moisture, some relations between distance from the pipe and moisture content were developed in two directions i.e. horizontal and vertical. It was shown that these relations have acceptable results in horizontal and vertical directions. Finally, the best depth of installation of the drip pipe and its drippers spacing were obtained as 20 cm and 50 cm, respectively, by considering the expansion of the wetted bulb and the development of salinity in the soil.

The simultaneous effect of salinity and drought stress are among the major factors that limit agricultural production in many parts of the world, especially in arid and semi-arid regions. Accordingly, a greenhouse research was carried out to study the simultaneous effect of salinity and water stress on yield and yield components of turnip (Purple Top White Globe var.) in Kashmar region. The experiment was performed as factorial arrangement in completely randomized design with three replications including two factors; salinity and irrigation water volume. Treatments consisted of four levels of water salinity (S1=0.7, S2=4, S3=8 and S4=12 dS/m) and three levels of water (W1=100%, W2=75% and W3=50 percent of water requirement), which were applied in a sandy-loam soil texture. The results showed that effects of salinity and water stress and their interaction were significant on biomass, shoot wet biomass, tuber and leaf dry weight (P<0.01). W1S1 and W2S1 treatments had higher biomass than the others. In all of the salinity levels, there was no significant difference between biomass in W1 and W2 irrigation levels. Based on the results of this research it could be concluded that turnip is more sensitive to salinity stress than drought stress. In other words, the results showed that the best level of salinity to reach the maximum biomass was S1. Therefore, the best treatment recommended for turnip planting in Kashmar region is W2S1.

 This study investigated the impact of improving surface water delivery and distribution systems on reducing groundwater abstraction. For this purpose, the current operational management of the Rudasht irrigation network, located in Isfahan province, was modeled and evaluated. Then, impact of two methods as the modernization alternatives, including an improved manual operation and an automatic control system by using the Model Predictive Control (MPC), was investigated. Operation of the canal system was simulated under two operating scenarios, demonstrating the operational status under the normal and water shortages conditions. Improvement of water supply and distribution process in the canal was evaluated using adequacy and dependability indicators of water distribution. In the next step, the amount of surface water replaced by groundwater was calculated by improving the process of water distribution in the main canal based on spatial analysis of the adequacy index. The results obtained from the operational simulation in the normal condition scenario showed improvement of the adequacy index by 5% and 32% and the dependability index by 7% and 21%, respectively, for the improved manual method and MPC. Moreover, the improvement in this scenario resulted in 3% and 25% reduction in the aquifer extraction, respectively, for the modernization alternatives. Operational simulation results under the water shortage scenario revealed 2% and 13% higher adequacy index, and 11% and 25% improvement in the dependability index by employing the improved manual and MPC approaches, respectively. This improvement resulted in 1% effectiveness for the improved manual method and 9% effectiveness for the MPC method in reducing aquifer abstraction under water shortage scenario. According to the spatial maps of the adequacy index obtained for the MPC method, this method can achieve more uniform and fair water delivery to farmers, especially under water shortage conditions.

Since agricultural sector is the largest consumer of water, it is crucial to introduce effective policies to manage water resources in this sector. In the present study, the economic analysis of allocation and pricing of irrigation water on cropping pattern and water demand management in Sistan plain was investigated by use of a positive mathematical programming model (PMP). In this regard, an economic modeling system including a state wide agricultural production model (SWAP) was used. The GAMS software version 24.1 was used to solve the proposed modeling system. The results showed that the use of pricing and allocation policies for irrigation water led to a decrease in the total area of designated cropping products and a reduction in the farm gross margins in Sistan plain. However, the aforementioned policies resulted in savings of 4.594 to 46.256 and 7.123 to 29.484 million cubic meters of water consumed in the region as a result of applying allocation and pricing, respectively. Decrease in total area of cultivation of selected crops under different scenarios of irrigation water quotas policy, especially higher economical crops such as watermelon, melon, and onion. Total gross yield of Sistani farmers would be reduced from 1425694 to 1292677 million Rials, reducing the gross profit by 2.17% to 9.33% in the region's agricultural pattern. Thus, applying the policy of water allocation could save about 30 million cubic meters of water available to farmers. Compared to pricing policy, the use of water allocation policy is recommended due to its superior effect on preserving water resources in the Sistan plain.

Moisture content of surface soil is an important variable in nature's water cycle, which plays an important role in the global equilibrium of water and energy due to its impact on hydrological, ecological, and meteorological processes. Soil moisture is a determining factor in many complex environmental processes and plays a determinative role in the occurrence of agricultural drought. In this study, based on estimated soil moisture data by SWAP model and data of the IPCC Fifth Assessment Report, agricultural drought was determined by the use of soil moisture deficit index for the future period. The climatic data was estimated using six GCM models and two RCP4.5 and RCP8.5 emissions scenarios, and downscaled by LARS-WG model, and was entered into the SWAP model. Finally, by using soil moisture data of 30 cm depth, agricultural drought was evaluated using SMDI index. The results of climate parameter changes showed that the minimum and maximum temperatures and rainfall in the future period would increase compared to the base period and RCP8.5 scenario estimated higher temperatures and less rainfall than RCP4.5 scenario. Results of estimated SMDI values for the future period showed that RCP4.5 scenario has a higher average of SMDI amount than RCP8.5 scenario. Also, both scenarios show the normal moisture amount for future period and the predicted SMDI amount for the future period is higher than the base period.

Water is one of the most important factors that limit agricultural development, especially in arid and semiarid regions around the world. One of the important data for water management is the amount of water requirement of different plants. In this regard, by measuring water input and output in lysimeters and using water balance equation, crop water use is determined. In this study, to determine crop coefficients of Milk thistle, as a valuable medicinal herb, a 1-year lysimetric experiment was conducted in Faculty of Agriculture, Birjand University, during the growing season of 2018. To conduct this project, six weighing lysimeters were used. To determine potential evapotranspiration as a reference crop, grass was grown in three lysimeters and, in three other lysimeters, Milk thistle (Silybum marianum L.) was planted. Based on the results, the reference crop evapotranspiration and actual evapotranspiration of the plant were equal to, respectively, 1179.5 and 920.2 mm, during the growing period of 177 days. The length of different stages of plant growth, including the initial, development, middle, and end stages was 22, 35, 70, and 50 days, respectively. Finally, based on the FAO method, the crop coefficient (KC) curve was drawn and the average of crop coefficient at each of four stages of plant growth was determined as 0.34, 0.69, 0.93, and 0.77, respectively.

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.