سالومه سپهری صادقیان

The water shortage in the agricultural sector in recent years and its continuation in the future is an undeniable reality in Iran. Super absorbent materials can be used to cope with the effects of drought and water stress on plants. As a result of absorbing and storing water, these materials can change the amount or frequency of irrigation water. To ensure the optimal development of the root structure of medicinal plants, aerial parts, and essential oil percentage, it is necessary to create optimal conditions for providing moisture. It is time-consuming and costly to conduct multiple tests to achieve this objective. Thus, simulation and optimization models have been suggested to solve this problem. The researcher must first prepare the required data for each combination of treatments mentioned in this model, then build a statistical model based on it. The next step is to determine the optimal conditions for the independent variables so that the dependent variables approach their maximum, minimum, or target value. According to the literature review, response-surface methodology (RSM) has been effective in determining the optimal values of factors in the agricultural sector. As a result, it can be also used to optimize the application of super absorbent in peppermint cultivation. So, this study was designed to optimize the use of super absorbent in different irrigation rounds to maximize quantitative and qualitative traits of peppermint (Mentha piperita).

The present research was conducted in the research greenhouse of the Agricultural Engineering Research Institute (AERI) in Karaj in 2018-2019. Specifically, three irrigation intervals (two, four, and six days) and three weight percent of Aquasource superabsorbent (zero, one, and two %W of superabsorbent/soil) were tested. Before irrigation, the moisture content in each pot was measured using a Lutron Professional Soil Moisture Meter (PMS-714), and the amount of irrigation in each round was determined based on the amount of moisture deficiency up to the field capacity (FC). The central square design is one type of response surface method. In this method, independent variables are determined to determine the predicted dependent variable through an experimental design. This design considers the average levels of the factors as the central point. Using this method, the experimental treatments are displayed as +1, zero, and ‒1, which represent the highest, average, and lowest levels of the independent variable, respectively. Using regression analysis of variance, linear terms, quadratic terms, and interactions between factors were added to the multivariate regression model to evaluate the model-data fit. Finally, the significance of the model and its accuracy in fitting the data were determined. To compare the obtained model results with observed values, the root mean square error (RMSE), normalized root mean square error (NRMSE), mean bias error (MBE), efficiency factor (EF), agreement index (d), and the coefficient of determination (R2), were used.

Variance analysis showed that the regression model for water productivity was statistically significant at the five percent probability level (P-value≤0.05) and for the other traits studied at the one percent probability level (P-value≤0.01). In contrast, quadratic regression was statistically significant only for root weight, root length, shoot weight, essential oil percentage, and water productivity traits. The regression of other traits was not statistically significant. Therefore, the RSM cannot be used to predict and optimize these traits. Based on the lack of significance of the lack of fit test, the results of regression analysis are reliable compared to variance analysis. The RSM was also confirmed to be effective in optimizing the traits studied. The overlapping map of the investigated parameters was prepared to determine the optimal limit and common surface. In the upper range of this map, which includes the most irrigation intervals and super absorbent consumption; parameters such as water productivity do not change much. This parameter reaches its maximum value in the center of the map. Generally, other parameters tend to reach the optimal limit within the range of the bottom right part of the map, so, to optimize the parameters of root weight, root length, shoot weight, essential oil percentage, and water productivity, their target values were determined as 1.1 kg m-2, 3 cm, 2 kg m-2, 3 %, and 4 kg m-3.

The effects of different irrigation intervals (three levels of two, four, and six days) and Aquasource super absorbent (three levels of zero, one, and two %W of super absorbent/soil) were examined on some peppermint plant traits. Results showed that the response-surface model did not significantly differ from statistical methods. As a result, it is possible to trust the results obtained. The traits of root weight and length, shoot weight, essential oil percentage, and water productivity were used in the RSM, and all other traits were found to increase with an increase in irrigation water, except for essential oil percentage and water productivity. In terms of essential oil percentage and water productivity, the reduction in irrigation intervals to +0.8 levels had an upward trend and then it declined afterward. Increasing the amount of super absorbent negatively affected the characteristics of root weight and length, shoot weight, and essential oil percentage. As the amount of super absorbent was increased to a range of -0.3, water productivity increased, and then the value of this parameter also decreased. As a result of these conditions, the RSM was effectively used to optimize the irrigation interval and super absorbent amount, and it was determined that the best conditions were obtained by utilizing a three-day irrigation interval with a super absorbent concentration of 0.3%. Therefore, compliance with these conditions is recommended for peppermint cultivation.

The basic strategy to mitigate water crisis is to save agricultural water consumption by increasing productivity, which will result in more income for farmers and sustainable production. Due to the economic importance of barley production in the country, it is necessary to study the volume of irrigation water and water productivity to produce this strategic product. Based on extensive field research on irrigation water management and application of different irrigation methods in barley farms, the innovations of this research were: a) measuring water consumed and determining water use efficiency in barley production, b) the up-to-date of the measurements and research findings, c) findings applicability for application in agricultural planning at the national and regional levels, d) the ability to development the findings in barley farms at the national level to improve water use efficiency. The hypotheses of this research are: a) barley irrigation water is various in different regions, b) water applied in barley farms is more than the required one, c) the water use efficiency of barley is different in the main production areas, and d) The applied water of barley is not the same in different irrigation methods. Therefore, the main objective of this study is to determine the water consumed and water use efficiency in barley production; to measure the water applied to barley farms in the main production areas; to compare the water measured in the production areas with the net irrigation requirement; and finally to determine water use efficiency of the barley in the main production areas in the Iran.

 For this purpose, the volume of irrigation water and barley yield in 296 selected farms in 12 provinces (about 75% of the area under cultivation and production of barley in Iran) including Khuzestan, East Azerbaijan, Ardabil, North Khorasan, Fars, Khorasan Razavi, Tehran, Semnan, Markazi, Isfahan, Hamedan and Qazvin were measured directly. Farms in the mentioned provinces were selected to cover various factors such as irrigation method, level of ownership, proper distribution and quality of irrigation water. By carefully monitoring the irrigation program of selected farms during the growing season, the amount of irrigation water for barley during one year was measured. At the end of the season and after determining the average yield of barley during the 2020-2021 year, the values of irrigation water productivity and total water productivity (irrigation+effective rainfall) were determined in selected barley farms in each region. The volume of water supplied was compared with the gross irrigation requirements estimated by the Penman-Monteith method using meteorological data from the last ten years, and compared with the values of the National Water Document. Analysis of variance was used to investigate the possible differences in yield, irrigation water and water productivity in barley production.

To assess the reliability of statistical analysis, we evaluated the sufficiency of the number of measurements needed for both the quantity of irrigation water and the ley yield on the farms. Subsequently, we computed statistical indices, such as the mean and standard deviation. The results showed that the number of measurements of irrigation water and barley yield was to be 296 and 283, respectively, which was more than the number of measurements required for irrigation water (41 dataset) and yield (50 dataset). Therefore, the sufficiency of the data for the statistical analysis was reliable. The results showed that the difference in yield, volume of irrigation water and water productivity indices were significant in the mentioned provinces. The volume of barley irrigation water in the studied areas varied from 1900 to 9300 cubic meters per hectare and its average weight was 4875 cubic meters per hectare. The average barley yield in selected farms varied from 1630 to 7050 kg ha-1 and the average was 3985 kg ha-1. Irrigation water productivity in selected provinces ranged from 0.22 to 1.53 and its weight average was 0.90 kg m-3. Average gross irrigation water requirement in the study areas by the Penman-Monteith method using meteorological data of the last ten years and the national water document were 4710 and 4950 cubic meters per hectare, respectively. Irrigation efficiency of barley fields in the country is estimated at 62-65% without deficit irrigation.

In order to reduce water consumption and improve water productivity, it is suggested to manage water delivery to farms during the season and deliver water rights to them according to crops water requirements. To reduce water losses and enhance productivity in the barley farms, it is suggested the application of modern irrigation systems according to the farms conditions with the suitable operation; and modification and improvement of surface and traditional irrigation methods. Note that, water is only one of several necessary and effective inputs in the optimal and economic production of barley. On the other hand, attention should be paid to the optimal application of other inputs including: seeds, fertilizers, equipment and tools etc.

The goals of irrigation modernization are mainly focused on increasing irrigation efficiency, improving water productivity, and ultimately reducing irrigation water consumption and saving scarce water resources in these countries. Meanwhile, various studies have shown that increasing irrigation efficiency and improving water productivity through the development of the use of efficient and modern irrigation systems, sometimes did not lead to real savings and reduction of agricultural water consumption as expected or vice versa, it has caused its increase. This phenomenon is called "rebound effect” of water. The concept of the rebound effect phenomenon is that with the use of efficient irrigation technologies, irrigation efficiency and water productivity increase, but part or all of the expected saved water may be offset by more water consumption. The effective factors and reasons for the rebound effect phenomenon are mainly: the increase in the irrigated area following the reduction of water consumption, the increase in evapotranspiration due to the change in the cropping pattern and increased crop yield, reduction in the quantity and quality of return flows due to increased irrigation efficiency, deficit irrigation to provide enough water for the increased cultivated area. In general, there is a need to mainstream the literature on the subject and following determining the extent of rebound effect and the necessary analysis, relevant hints to the policy makers and those responsible for the development of new irrigation technologies should be given to adopt a suitable policy and to take actions to implement technical, economic-social and political solutions.

In this study, the area under cultivation, average irrigation water and orchard yield were determined by field studies by researchers. Indicators of water consumption, virtual water, water productivity, virtual water consumed and water consumption intensity were obtained. Then, using irrigation planning, the amount of irrigation water was evaluated for the conditions of reducing water consumption in orchards. The best conditions for each crop were selected based on the results obtained and compared with the current conditions. According to the results, in most garden products, it is necessary to reduce water consumption compared to the current situation. The largest decrease was observed in peach, apple, nectarine and grape crops. The difference between water consumption for these products in the current and optimal conditions was 0.7, 6.4, 6.3 and 5.7 million cubic meters, respectively. The lowest difference between water consumption in the current and optimal conditions was determined in pomegranate and pistachio products with a difference of 0.12 and 0.35 million cubic meters. The average of virtual water consumed by horticultural products in Alborz province in the current situation is 0.0133 million cubic meters, which in the optimal case decreased to 0.0109 million cubic meters. Therefore, with the reduction of water consumption in orchards, the intensity of water consumption decreases from 0.33 to 0.26. This will save 19% of the province's water resources.

The purpose of this study was to assess irrigation management and determine water productivity in olive orchards managed by local farmers in the country. To achieve this, the amount of water provided by gardeners and the yield of 102 olive orchards that underwent irrigation using various methods, surface and drip irrigation, were measured across the provinces of Qazvin, Fars, Zanjan, Gilan, Golestan, and Semnan. This data was collected during two consecutive years, 2018 and 2019. Measured values were compared with NETWAT-estimated net irrigation requirements as well as Penman-Monteith-derived values. Based on the results, it can be concluded that the average volume of irrigation water, yield, irrigation water productivity, and applied water productivity in the selected provinces are significantly different at a probability level of 1%. According to the study, the volume of irrigation water used in olive orchards varied from 2848 to 11463 m3/ha, with a weighted average of 6011 m3/ha. The average yield of olives in the production poles of this product has varied from 1500 to 11000 kg/ha over the two-year period, and its weighted average has been 4867 kg/ha. It is also worth mentioning that the water productivity ranged from 0.2 to 2.40 and its weighted average was 0.95 kg/m3. Furthermore, the applied water productivity in the selected provinces ranged from 0.18 to 1.45 and its weighted average was 0.63 kg/m3. Upon evaluating the efficiency of irrigation in the olive orchards, it was observed that the quantity of water delivered was approximately 27% and 17% less in comparison to the irrigation requirement calculated using recent 10-year meteorological data and NETWAT, respectively. In other word, forced deficit irrigation has taken place in the olive orchards

Alborz province is considered as one of the most important agricultural regions in Iran that annually most of the water resources in this province are allocated to the agricultural sector. The concept of virtual water is considered as a tool to examine the status of agricultural production in each region based on water consumption. For this reason, in the present study, using the data collected during the last ten years (2011-2021), the amount of virtual water trade in Alborz province was investigated. The results showed that the water deficit index of Alborz province is 0.6. The water self-sufficiency index of this province in relation to the import of virtual water is 100. Therefore, in this province, mainly agricultural products are exported and this province is self-sufficient in producing agricultural products and importing virtual water. To improve the water situation of Alborz province, different scenarios were investigated using the AquaCrop model and the optimal amount of water for irrigation of each crop was determined. With the improvement of the existing irrigation situation, the virtual water exported to most crops decreased. The highest decrease in virtual water exports for barley, lettuce and celery, potatoes and cabbage was achieved with the values of 1.6, 0.97, 0.16 and 0.13 million cubic meters per year, respectively. Also, by applying optimal irrigation scenarios, the water shortage index of Alborz province decreased to 0.54, which was less than 0.06 compared to the current situation.

Drought and water shortage in Iran is a climatic fact and due to the growing need for water in different sectors, this problem will become more acute in the coming years. Therefore, managing water consumption and applying advanced techniques in the agricultural sector as the largest consumer of water in the country, can be very helpful. One of the most effective strategies to improve water productivity in agricultural sector is to use hydrogel polymers to improve soil texture, increase soil water retention, reduce erosion and increase germination (Nirmala and Guvvali, 2019). However, in general, due to differences in the synthesis and chemical structure of polymers, the water uptake and storage capacity of these hydrophilic polymers are different, and hence their effect on changes in soil moisture and storage capacity will be very different (Yu et al ., 2017). The aim of this study was to investigate the effect of different levels of Aquasource hydrogel on yield, yield components and water productivity of peppermint (Mentha piperita) at different irrigation intervals.

Today, one of the most important challenges of the present and the future, especially in the arid regions of the world, is the issue of water shortage and in some cases the water crisis. One of the ways to improve water productivity and better water management in agricultural sector as the largest consumer of water is the use of super-absorbent materials to improve soil texture, increase soil water retention, reduce erosion and increase germination. The aim of this study is to evaluate the effect of Aquasource superabsorbent polymer on physical parameters and soil-water characteristic curves (SWCC) of different soil textures.  

Aquasource is a new generation of potassium-based superabsorbent polymers that are biodegradable and free of destructive acrylamide compounds. In order to evaluate the effect of Aquasource hydrogel on hydro-physical properties of soils, some experiments in the form of a completely randomized design with 3 replications was performed. The first factor was different levels of superabsorbent (0, 0.5, 1 and 2% by weight of superabsorbent/soil) and the second factor was three different soil textures (sandy-loam, clay-loam and silty-clay). SWCCs related to all treatments were determined by determining the moisture content of the samples at different pressures (0, 0.3, 0.5, 1, 3, 6, 9 and 15 bars) using a pressure plate device. Then, to obtain the soil moisture characteristic curve parameters  in each sample, two softwares RETC (v.6.02) and Rosetta (v. 1.1) were used.  

The results of variance analysis and mean comparisons based on Duncan's test showed that in all soil textures studied, the application of superabsorbent and the increase Aquasource amounts, increased the moisture contents at the field capacity and permanent wilting point. However, the highest amount of soil available water for plant use in sandy loam, clay loam and silty clay textures was 9.8%, 13.8% and 12.7%, respectively, and they are related to the use of 0.5% w/w of superabsorbent in these treatments (Fig. 1). The use of larger amounts, up to 2%w/w, reduced the soil available water for plant use. This issue can be related to the reducing the interaction of soil particles and polymers with increasing the amount of superabsorbent application in soil. At high levels of superabsorbent consumption, the contact of the hydrogel with the soil particles is reduced, followed by the aggregation of the superabsorbent. This prevents the proper exchange  between the superabsorbent and the surrounding soil, and thus despite the presence of moisture in the soil-superabsorbent system, this moisture cannot be used for the plant, so that in all three soil textures the lowest amount of plant available water belongs to the treatments of 2% w/w of Aquasource. The results of statistical analysis for estimating the parameters of the soil-water characteristic curve due to the application of different levels of superabsorbent in different soil textures using two software RETC (v.6.02) and Rosetta (v. 1.1) showed that the fit The Van-Genuchten (Moallem) model in RETC software in all treatments has provided a good approximation of the parameters of the soil-water characteristic curve (R2> 0.98). Also, with increasing the amounts of superabsorbent, the accuracy of the model in estimating the parameters decreased to some extent.    

Application of Aquasource superabsorbent and increasing the application level of this superabsorbent polymer (from 0 to 2% by weight of superabsorbent/soil) in sandy-loam, clay-loam and silty-clay soil textures caused an increase in the moisture content at field capacity and permanent wilting point. Application of 2% W/W in sandy-loam, clay-loam and silty-clay soil textures increased the moisture content at the field capacity by about 2.4, 1.6 and 1.5 times, respectively, compared to the control treatments of each soil textures. However, the highest amounts of plant available water in all three soil textures were obtained by applying 0.5% W/W (superabsorbent/soil). Application of 0.5% W/W in sandy loam, clay loam and silty clay textures increased the plant available water by about 1.23, 1.19 and 1.12 times compared to the control treatments in each soil textures, respectively. However, the use of larger amounts reduced the plant available water. At low levels of Aquasource application, the interaction between the   superabsorbent polymer and the soil particles in the soil/polymer system facilitates the transfer of moisture stored in the superabsorbent to soil particles. However, increasing the application level of this polymer up to 2% W/W has an inhibitory effect and in this case, the interaction between the polymer and soil particles is reduced, which leads to a lack of proper drainage of moisture from the polymer.   Acknowledgement The authors would like to thank Agricultural Engineering Research Institute for supporting this research.

Safflower is one of the most important oil crops whose yield decreases under water stress. Therefore, determining its response to different irrigation water managements is very important. To do that, in this study, AquaCrop model was used to simulate three irrigation scheduling strategies of safflower for drip, subsurface drip and furrow irrigation methods. At first, AquaCrop was calibrated using data collected from a research farm located at 34˚ 21’ N and 47˚ 9’ E, in Kermanshah, Iran. In the first strategy, apply irrigation up to field capacity at a constant rate (1, 5, 10 and 20 days), in the second strategy, apply a constant amount of irrigation water (values of 10 to 50 mm for drip and subsurface drip irrigation methods and values up to 10 90 mm for furrow method at constant duration 2 and 4 days for drip and subsurface drip irrigation and 10 and 20 days for furrow) and in the third strategy apply water stress levels of 100, 66 and 33% during the growing season for all three Irrigation method was considered. The results showed that the highest yield, biomass and water productivity were obtained in the first and second strategies. Maximum values for yield and biomass were 3.7 and 12.2 fon.ha-1, respectively, and maximum water productivity was 0.54 kg.m-3 in both drip and subsurface drip irrigation and 0.69 kg.m-3 in furrow irrigation. As the second strategy is easier for farmers to implement, it is suggested that this method be used. Therefore, for drip irrigation and subsurface drip scenario, it is recommended to apply 10 mm of irrigation water with a period of two days, and apply 30 mm water irrigation with a period of 10 days.

< 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.

In this research, the effect of different levels of sprinkler irrigation and planting density on yield and Water Use Efficiency (WUE) of middle-aged and early varieties of grain maize (KSC500 and KSC302) evaluated under sprinkler irrigation method for two years in Karaj. This research was carried out as two independent split plot experiments in a randomized complete block design with three replications. The applied water levels in both experiments were the same (three irrigation levels: 75,100 and 125% of the Etc). However, according to the variety, in each experiment, the planting densities were different (in the case of KSC500 variety, sub plots were three plants densities including 75000, 85000 and 95000 plant per hectare and in the case of KSC302 variety, three plants densities including 80000, 90000 and 100000 plant per hectare were considered. The results showed that increasing the depth of irrigation water significantly increased the grain yield of maize. However, different planting densities had no significant effect on yield and WUE of the mentioned cultivars. Based on the results in the range of the irrigation depth from 700 to 1000 mm, the yield of maize varieties was linearly increased. However, with further increase in the depth of irrigation water, the slope of the relationship between the yield and irrigation water decreased significantly. In the first experiment (KSC500), applying 75% of the ETc has led to the highest WUE (0.944 kg/m3) and in the second experiment (KSC302), applying 100% of the has led to the highest WUE (1.03 kg/m3). Finally it can be concluded that under limited water resources conditions, planting early and middle-aged varieties of maize, using proper irrigation scheduling and applying about 9500 m3/ha of irrigation water in Karaj region under sprinkler irrigation method, can lead to an increase in maize WUE up to 1 kg/m-3 or more.