مجله پژوهش آب در کشاورزی
سال سی و چهارم شماره 3 (پاییز 1399)

Estahban region in Fars province is mostly covered with rainfed fig trees. Gardeners have applied over-irrigation because of drought in recent years. In this study, irrigations were scheduled based on different crop water stress indexes by measuring canopy temperature. The treatments included irrigation at different Crop Water Stress Indexs (CWSI) of 0, 0.2, 0.4, 0.6, 0.8. A rain-fed treatment was also added as control. The trees were irrigated by hand using water tankers. During the two years of the research, the number of irrigations, yield, and water productivity were measured. Duncan test was used for statistical analysis of the treatments in a complete block test design with four replicates. Economical analyses were also done based on benefits and costs in 2017 and 2018. Results showed that the maximum observed CWSI was not more than 0.6. Irrigation increased the yield values from 3.1 kg/tree in rain-fed condition to 9.8 kg/tree in the fully irrigated treatment. However, water productivity decreased from a large value in the rainfed treatment to 0.65 kg/m3 in the fully irrigated treatment. The treatment that was irrigated once had amuch increase in yield and increase about 740000 and 1190000 Rials in net benefit compared to rain-fed treatment in the studied years. The net benefit of one irrigation in the two studied years was about 530000 and 990000 Rials/m3of applied water. These values decreased with increase in the irrigation times. The benefit cost ratio in the two studied years was 1.10 and 1.46 for rain-fed trees while it was 2.21 and 2.89 for single irrigation treatment, respectively. Therefore, by one supplemental irrigation of the rain-fed fig trees,the drought damages could be controlled, a significant economical benefit could be gained, and over-irrigation is avoided.

In order to know the technical status of the irrigation systems and determine the amount of achievement of the objectives of the design stage, it is necessary to evaluate these systems.In this study, 18 classic fixed sprinkler irrigation systems with mobile sprinklers implemented in different parts of Ardabil plain in the summer of 2019 were evaluated. For this purpose, criteria such as Christiansen Uniformity Coefficient (CU), Distribution Uniformity (DU), Potential Application Efficiency of Low Quarter (PELQ),and Actual Application Efficiency of Low Quarter(AELQ),were used at both block and system scales.After measurements and collection of the required information, these criteria were calculated. The mean values of the criteria were for the blocks were 83.46%, 74.96%, 68.93% and 67.94%, respectively, and for the systems, they were82.32%, 73.43%, 65.71% and 66.70%, respectively. In addition, Wind Drift Losses (WDEL), Deep Percolation losses (DP) and irrigation adequacy (ADirr) were found to be, 7.95%, 6.97%and 27.08%, respectively. Results and field studies showed that low values of PELQ and AELQ were affected by inappropriate spacing of sprinklers, lower pressure compared to design pressure, high pressure changes in the system and simultaneous use of large number of sprinklers. In addition, inaccurate management in operation, land topography and long lengths of pipes are effective factors in reducing the actual performance indicators of irrigation systems in Ardabil plain. Among the suggested recommendations are a revision of the designs, due consideration of the land slope, change in the type of sprinklers, or even change in the orifice of the sprinklers.

< p >  < p >In Khuzestan Province, drainage water production from various activities, especially agriculture, is a serious problem. In order to optimize the use of drainage water, cultivation of salinity resistant crops can be considered as a suitable practice. Therefore, in 2019, a study was conducted to investigate the possibility of recycling drainage water of sugarcane fields for winter cultivation of quinoa  in the Research Farm of Mirza Kuchak Khan Sugarcane Agro-Industry Company in southern Khuzestan. This study was performed as split plots with a complete randomized block design with two factors and three replications. The main factor was the management of irrigation water including the use of Karun river water, drainage water of sugarcane fields, and intermittent-periodic irrigation (alternating application of Karun water and drainage water). The sub-plots were allocated to four genotypes of quinoa including "Giza1, Titicaca, Rosada, and Q26". Interaction of irrigation water type with genotype showed that the highest biomass in terms of dry forage (3645.6 kg/ha) belonged to Giza1 genotype using irrigation with Karun water, which statistically had no difference with the Rozada biomass (2620 kg /ha) using irrigation with drainage water. Monitoring of soil "ECe" and "ESP" during the growing season showed that for the two treatments of irrigation with the water of the Karun River and intermittent-periodic irrigation, the farm soil up to 1 meter depth was non saline and non-sodic. This is while before cultivation of quinova, the soil layer of 0- 25 cm was saline (5.54 dS/m) and the deeper parts were non-saline. In irrigation with drainage water, the 0-25 cm layer soil remained saline due to the effect of evaporation. However, in layers deeper than75 cm, due to the accumulation of salts compared to pre-planting (ECe=2 dS/m), salinity reached ECe=4dS/m and ESP=7%. These results indicate the need for leaching at the end of the growing season and the importance of drainage for salt outflow from agricultural lands to maintain soil salt balance in areas where drainage water recycling is practiced.

The present research was conducted in 2017 with the aim of investigating the possibility of using solar energy (photovoltaic systems) compared to energy from national network of electricity in three irrigation systems of Tape, Center pivot, and Fixed classical sprinkler irrigation in Alborz province. At first, 2 dominant crops in the region (wheat and maize) were identified and the water requirement of these crops was determined under Karaj conditions. Then, the energy needed to supply the necessary power in each of the irrigation systems using the electricity network and solar power was determined. Afterwards, the number of solar panels needed to supply this amount of energy and the initial cost for the construction of the solar system was examined, as well as the costs of using the electricity network. Then, by evaluating the crops yield performance in the region and its economic value, the profitability of the products was determined in the region.  The t-test was used to determine the difference between the mean cost and revenue or profit of the systems statistically. According to the economic results in the analysis period, in network electricity with irrigation systems of Fixed classical sprinkler, Center pivot, and Tape irrigation, net present value was estimated as 753.7, 770.3, and 1212.2 Iraniak million Rials, and benefit cost ratio in these systems was estimated at 1.64, 1.67 and 2.1. In solar system with irrigation systems of Fixed classical sprinkler, Center pivot, and Tape irrigation, net present value was estimated as 322.6 , 713, and 988.8 Iraniak million Rials, and benefit cost ratio in these systems was estimated at 1.2, 1.59, and 1.73. Therefore, based on profitability indices, national power network with drip irrigation system treatment is recommended as the better treatment.

To determine crop coefficient and evapotranspiration of Thymus daenensis Celak., an experiment was performed in 2016 using lysimeters (direct method) and computational method In the direct method, drainage lysimeters with underground structures located at Alborz Research Station in Karaj were used. Each of the lysimeters were 0.9 meters in diameter and 1.28 meters high. In each lysimeter, a seedling of Thymus was planted. Then, two main lysimeters were selected and their irrigation was adjusted to the field capacity. On both sides of the main lysimeters, similar lysimeters were considered as margins. During the experiment period, the input and output water of the lysimeters as well as dry weight of aerial parts, the amount of  evapotranspiration, and water use  efficiency in Thymus daenensis were measured. In order to estimate the evapotranspiration of the reference plant, the computational methods of Blaney Criddle and FAO Penman-Monteith were used. Thymus plant coefficients during plant growth, was obtained as the ratio of Thymus evapotranspiration to reference plant evapotranspiration. Based on the results, the amount of cumulative evapotranspiration of the reference plant by Blaney Criddle-FAO and Penman-Monteith-FAO were 715 and 631 mm, respectively. In lysimeters, Thymus evapotranspiration up to the beginning of flowering was 100 mm, to the beginning of seed production  455 mm, and to the end of seed production  622.13 mm. The Thymus plant coefficients in initial, crop development, mid-season and late-season stages were 0.33, 0.65, 1.20, and 0.99, respectively. Water use efficiency was estimated to be 0.4 gL-1. By determining the plant coefficient and water requirement of Thymus, in addition to helping in design of intelligent systems and mechanized irrigation, it will be possible to plan and manage irrigation during the plant growth period.

Water and soil resources of the country are limited, and the optimal use of water resources in agriculture requires estimation of the exact amount of water consumption by different plants in different conditions. This study was conducted to investigate evapotranspiration, crop coefficient, and water requirements of salicornia under lysimetric conditions in a factorial experiment with completely randomized design. The experimental treatments were two species of salicornia (Salicornia bigelovii and Salicornia persica) and two levels of irrigation water salinities (8 and 25 dS.m-1) in three replications. The actual evapotranspiration (ETa), reference evapotranspiration (ET0), and crop coefficients (Kc) of salicornia species were determined at three main salicornia growth stages. The results showed that increase in irrigation water salinity from 8 to 25 dS.m-1caused significant changes in yield (biomass and seed yield) of the two salicornia species at the 1-percent probability level. Moreover, the amount of irrigation water consumption in different treatments and replications varied from 28 to 33 thousand cubic meters per hectare. For the salinity level of 8 dS.m-1, the Kc values at the beginning, middle, and end of growing season of bigelovii specie were obtained as 1.18, 1.55, and 1.42, respectively, while for the salinity level of 25 dS.m-1, these values were 1.06, 1.37, and 1.26, respectively. For persica specie, the Kc values of the beginning, middle, and end of the growing season were 1.37, 1.58, and 1.10 (for salinity level of 8 dS.m-1) and 1.15, 1.38 and 1.27 (for salinity level of 25 dS.m-1), respectively. In addition, water use efficiencies of salicornia varied from 0.21 to 0.38 kg.m-3 at different treatments and species.

Drought is one of the major constraints on agricultural productivity worldwide. Selenium plays an important role in plants tolerance to environmental stresses by increasing the levels of antioxidant enzymes and compounds. In order to investigate the effect of selenium on some growth and physiological characteristics of the Dragons head (Lallemantia iberica), a factorial experiment was conducted in a completely randomized design with three replications in greenhouse conditions. Treatments included different levels of drought stress (100%, 75%, 50% and 25% field capacity) and different concentrations of selenium (0, 5 and 10 mg.L-1 sodium selenate). Foliar application of sodium selenate was performed in two stages. According to the results, drought stress had a negative effect on fresh and dry weight leaf and yield. But, under drought stress conditions, foliar selenium caused a significant increase in plant height (32.2 cm), proline (0.92 mg/g DW), and total phenol (0.82 mg/g DW) content. Increase in selenium concentration increased Dragons head physiological properties: relative leaf water content (65.10 %), total soluble sugar (2.55 mg/g DW), soluble protein (0.289 mg/g DW), and antioxidant activity (0.21 %). Concentration of 10 mg.L-1 sodium selenate had a positive effect on plant fresh weight and biological yield of Dragons head, which was probably associated with the antioxidant role of selenium. Under drought stress, selenium increased the amount of proline and total phenol, which increased these adaptation osmolytes and had an important role in the drought tolerance of Dragons head.

Peppermint (Mentha piperita L.) is used for medicinal and food purposes. Its cultivation has economic importance, due to its ability to produce and store essential oil. This research was conducted to study the effect of deficit irrigation and magnetized water on yield and yield components of peppermint in the experimental research greenhouse of Ferdowsi University of Mashhad, during 2018-19. We used a factorial experiment based on the completely randomized design with 3 replications. Irrigation levels consisted of 4 levels (100%, 85%, 70%, and 55% of plant water requirements) and magnetic field factors consisted of 3 levels (0, 0.3, and 0.6 teslas). The result showed that decrease of the water requirement by 15%, 30%, and 45% resulted in reduction of shoot fresh weights by 11.2%, 15.1%, and 36.5%, respectively. However, irrigation with magnetized water (0.3 teslas) under deficit irrigation levels (85%, 70%, and 55% of plant water requirements) resulted in the increase of shoot dry weights by 19.5%, 24.7%, and 66.4%, respectively. In general, the use of magnetic water under water stress enhanced plant growth and improved dry and wet shoot yield in peppermint compared to the control treatment under deficit irrigation conditions.

Annual and seasonal rainfall distributions are the main determinants of yield in rainfed conditions, of which seasonal rainfall is more important. Therefore, it is necessary to provide precipitation indicators that have a significant conceptual relation with crop performance fluctuations. In the present study, the relation between rainfall uniformity indices and rainfed wheat yield in Tabriz plain was evaluated in 19-years period. Also, in order to examine the effect of precipitation more accurately, the Rain-Time Index [M1] [M2] (RTI) was used, which could indicate the effect of simultaneous changes of the two factors of rainfall time and rainfall amount on crop yield fluctuations. The results showed that the correlation between rainfed wheat yield and slope of uniformity line (ratio of cumulative precipitation per length of growing period) was significant at 1% level. However, there was no significant correlation between the uneven distribution index and yield. Also, according to the obtained results, the first effective rainfall event is the most effective rainfall event on the yield of rainfed wheat. It seems that the inadequacy of effective spring rainfall, which is one of the main reasons for the low yield of rainfed lands, prevented the explanation of the positive effect of late season rainfall on yield. Therefore, in order to evaluate the effect of intermittent precipitation and Rain-Time Index [M3] [M4] on yield more accurately, a single supplementary irrigation should be applied at the stage of grain filling and its effect on the studied indicators and yield should be investigated.

The purpose of this research was to identify the barriers and the support needed for farmers' participation in the water transfer and distribution plan in the agricultural lands of Sistan Plain. The study included qualitative methods of data collection, such as reviewing documents related to the plan, and quantitative method of data collection by using a questionnaire. The validity of the content was confirmed by interviewing some experts of Zabul Agricultural Jihad and the research team, and the reliability of the questionnaire was confirmed by calculating Cronbach's alpha (0.887) for barriers to participation, and farmers' required support for participation in the project (0.973). The statistical population consisted of farmers in Sistan plain (N = 6000), 360 of whom were selected as the sample of the study. Factor analysis of barriers to farmers' participation in the water conveyance project resulted in the extraction of four factors: "trust", "information and knowledge", "inefficiency and deficiency" and "climate and drought conditions"; and these factors explained 57.9% of the total variance of the variables. Also, factor analysis of the support needed by farmers to participate in the water transfer project resulted in the extraction of three factors: "technical and institutional support", "emotional support" and "legal support"; and these factors explained 67.3% of the total variance of the variables.

Groundwater resources in the world are experiencing significant reductions due to climate change and drought. Therefore, in order to make appropriate decisions by managers and planners, forecasting and studying the economic effects of drought is essential. Thus, the purpose of this study was to investigate the welfare effects of drought on groundwater beneficiaries. Accordingly, the present study investigated the economic effects of drought and its impact on the cultivation pattern of the southern Mahyar Plain and changes in social welfare in the 2016-2017 crop years, using the groundwater market approach. For this purpose, three approaches of regression estimation, positive mathematical programming, and dynamic programming were used. The results showed that in drought conditions, the area under barley and wheat cultivation increased and the area under corn decreased. Other results showed that the reduction of water supply due to drought would reduce the social welfare by 1020 million Rials (based on 2016 prices). Therefore, it is suggested that the amount of welfare lost by farmers due to water shortages should be a criterion for determining the amount of compensatory payments.

This study was conducted to evaluate the effects of exogenous applications of salicylic acid on improvement of drought tolerance in Madagascar periwinkle (Catharanthus roseus L.). The experiment was arranged as factorial based on a completely randomized design (CRD). Salicylic acid concentrations of 0, 0.5, 1, 1.5 mM were foliar sprayed on pot plants treated with three levels of irrigation including 30%, 60%, and 100% Field Capacity). Application of salicylic acid was repeated three times with three-day interval, while plants were exposed to drought stress for four weeks. The traits such as flower number, flower diameter, fresh weigh of individual flower, shoot number, and water use efficiency (WUE) were evaluated in this study. Based on the results, the effect of salicylic acid on severe deficit irrigation (30% PC) was significant, and the highest number of flowers at this level was observed in foliar application of 0.5 and 1 mM salicylic acid. Also, the highest fresh weight of single flower and number of sub-branches were obtained in application of 0.5 mM salicylic acid under severe deficit irrigation. In addition, exogenous salicylic acid at all levels significantly improved the flower diameter, which could have a major impact on the aesthetic properties of this plant under deficit-irrigation conditions. In total, due to availability of salicylic acid and easy use, foliar application of salicylic acid at 0.5 mM concentration would be recommended to improve Madagascar periwinkle drought tolerance under severe deficit irrigation.