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Because of the excessive use of nitrogen fertilizers, most of the groundwater resources are contaminated in the upstream of the Zayandehrud basin. This study set out to investigate the effect of different levels of water and nitrogen on yield, soil nitrogen, as well as water productivity indices of winter wheat and barley. The experimental treatments were of three nitrogen levels: no nitrogen fertilizer (N0), 50 kg N ha−1 (N1), and 150 kg N ha−1 (N2), as well as two irrigation levels containing deficit irrigation (I1) and full irrigation (I2). Each treatment was repeated three times. Wheat yield for I2 was 5,640 kg ha−1 and for I1 was 3,720 kg ha−1. The yield for barley was 5,620 and 3,850 kg ha−1 for I1 and I2, respectively. The irrigation water productivity (WPi) was increased by 55% for wheat and 83% for barley under deficit irrigation level. We recommend the use of 50 kg ha−1 (instead of 150 kg ha−1), knowing that it reduces the yield and water productivity for wheat by 11.7 and 10.9%, and by 14.5 and 12.6% for barley, respectively. In contrast, the soil nitrogen residual for wheat and barley was reduced by 56.6 and 66.1%, respectively, thus greatly reducing the risk of contamination of groundwater resources. HIGHLIGHTS NO3− concentration in water from 120 wells was measured.; Using high N fertilizer by farmers caused the increase in nitrate in groundwater.; Deficit irrigation is a good strategy to increase WP in a water-scarce arid area, for wheat and barley.; Using 50 kg N ha−1 instead of 150 kg N ha−1 is a good strategy to protect the environment; however, it may slightly reduce yields.;

Abstract This study evaluated the interaction effects of irrigation level (well-watered and water stress conditions) and inoculation by different mycorrhizal species (non-inoculated, Funneliformis mosseae, Rhizophagus irregularis, Claroideoglomus claroideum, and Glomus fasciculatum) on mycorrhizal colonization, antioxidant activity, seed yield and oil quality of two sesame cultivars (Yekta and Naz). Water deficit decreased mycorrhizal colonization, seed yield and oil concentration but increased antioxidant activity and seed total phenol and flavonoid concentrations. However, mycorrhizal inoculation increased antioxidant activity, seed yield, oil concentration and total phenolic and flavonoids. The lowest reduction by water stress and the highest increase by inoculation in seed yield were observed in Naz plants inoculated by Cl. claroideum. Principal component analysis showed the highest differentiation effect of water stress compared to mycorrhizal inoculation on both cultivars, indicating the relative sensitivity of the two cultivars to water deficit. However, the application of different species of mycorrhizal fungi versus the non-inoculation conditions was somewhat discriminative. In terms of fatty acids, in most cases, water stress increased oleic, palmitic and stearic acids and decreased linoleic and linolenic acids but inoculation increased oleic and linoleic acids and decreased linolenic, palmitic and stearic acids. Regarding phenolic and flavonoids components, the contents of chlorogenic and caffeic acids were increased by water stress but no consistent trend was noted in response to water stress for the other compounds. Mycorrhizal inoculation generally decreased chlorogenic acid but increased gallic, caffeic, p-coumaric, and ferulic acids. In conclusion, the results of the present study may help to increase the level of valuable compounds in sesame for further pharmaceutical purposes under water stress conditions and mycorrhizal symbiosis.

Considering the plant's positive response to nitrogen, farmers consume nitrogen fertilizers as much as possible. Excessive consumption of nitrogen fertilizers imposes additional costs on farmers, environmental pollution and direct negative impact on human health. Therefore, it is important to determine the amount of nitrogen-nitrate in the soil, plant and irrigation water in order to use nitrogen fertilizers optimally. In addition, according to the nitrogen balance, the amount of nitrogen deficiency is calculated and given to the plant, therefore the overuse of fertilizer is avoided. Most of the usual methods for nitrate measurement are time-consuming and expensive, spectroscopic measurement (spectrophotometer) makes it possible to determine the amount of nitrogen-nitrate in each of the soil, water and plant in the shortest time, inexpensively and accurately. In this research, we introduced a quick method of measuring the amount of nitrate in each of the water, soil and plant. The results are presented in terms of practical units in the field and soil for farmers and students, including kilograms of nitrogen per ton of product and the amount of nitrogen given through irrigation or nitrogen available in the soil in kilograms per hectare.

Determination of an appropriate location for monitoring soil water content (SWC) is a key factor in efficient use of water in precision agriculture, however, the main challenge is the dynamic movement of water and root development in the soil profile. The objective of this study was investigating how SWC distribution in a loam soil profile at two growth stages of maize may impact the suitable location for SWC monitoring in a drip-tape irrigation system. A new concept, Average Moisture Representative Surface (AMRS) was proposed to determine the surface of the soil profile, which represent the average soil moisture of the wetted volume. SWC samples were taken during two irrigation intervals (48~52 days after planting (DAP) and 68~73 DAP) and root growth pattern was studied through root length density (RLD) at 50 and 100 DAP. The results revealed that a non-uniform wetting pattern after irrigation limits the appropriate locations for SWC monitoring to point measurements and with time, SWC depletion resulted in enlarging AMRS. At the end of growing season, an increase of root growth around the drippers increased the variation of root water uptake in different soil layers, and thus optimal place for soil sensors was limited to the upper layers, where the maximum root water uptake occurred. Overall, it is recommended to install soil sensors, such as tensiometers and TDRs at a horizontal distance of 5~20 cm from the crop and a depth of 10~20 cm from the soil surface while drip-tape is aligned close to the maize row.

Decision support system tools such as crop models and considering the uncertainties associated with them are important for making an informed decision to fill the yield gap in farms and increase food security. This study’s objective was to identify and quantify the degree to which crop management practices, as well as climate and soil, affected the uncertainty of total biomass, evapotranspiration, and water productivity of silage maize by using a crop model and spatiotemporal input data. Using a calibrated crop model (DSSAT) and pSIMS platform, three planting dates by considering ten ensemble weather data and three soil profile data were simulated for the time period between 2002 and 2017 with a 2 km × 2 km resolution across maize production areas with arid and Mediterranean climates in Isfahan province, Iran. Additionally, the findings were used to determine the yield gap in the studied area to identify opportunities to boost food production. Our results showed larger uncertainty in Mediterranean climates than in arid climates, and it was more affected by planting date than weather parameters and soil profile. The accuracy of total biomass prediction by using pSIMS-CERES-Maize based on the spatiotemporal input data was 1.9% compared to field experimental data in the dry climate, and the yield gap based on the comparison of modified-pSIMS-CERES-Maize and reported biomass was 6.8 to 13 tons ha−1 in the arid and Mediterranean climate. Generally, all results represented the importance of using crop models and considering spatiotemporal data to increase reliability and accuracy, especially in Mediterranean climates, and their potential to increase food production in developing countries with limited water resources and poor agriculture management.

Water stress is a major factor that limits agricultural crop production. Silicon (Si) is generally considered as a beneficial element for the growth of higher plants, especially for those grown under stressful environment. This study was conducted to examine the effects of Si on growth and development of strawberry (Fragaria × ananassa ‘Camarosa’) under water stress conditions. A factorial experiment, in a completely randomized design, was used to investigate the effects of three irrigation levels and four Si treatments consisting of 0, 5, 10, and 15 mmol·L−1 potassium silicate (K2SiO3). The results showed that an increase in the levels of water stress caused a decrease in most of the quantitative characteristics such as specific leaf area, chlorophyll fluorescence, net photosynthesis rate, and stomata conductance; addition of Si significantly increased most of the mentioned factors; water stress increased electrolyte leakage, proline, and water use efficiency (WUE); Si treatment significantly decreased transpiration rate and improved chlorophyll content and WUE. Water stress stimulated mineral nutrient absorption whereas Si application decreased it under water stress. In conclusion, it was found that in most of the investigated factors, 10 mmol·L−1 potassium silicate had the best effect on growth and development of strawberry. Besides, Si application had beneficial effects on strawberry plants and the addition of it could alleviate water stress. Keywords: Fragaria × ananassa, potassium silicate, water stress, photosynthesis, mineral nutrient

Introduction: World's population growth and limited water resources and needing to more food production led to interest farmers to use nitrogen fertilizer more than soil requires and subsequently Nitrate leaching causes groundwater and environmental pollution. Therefore, researches has concentrated on improvement of nitrogen use efficiency, which numerical simulation is the effective solutions to optimize the management of water and fertilizer in the field in order to achieve the maximal yield and minimal nitrate pollution of soil, groundwater and drainage in water deficiency crisis condition. For this reason, the evaluation of new user friendly models in correct estimation of soil moisture and nitrogen content distribution and recognition of water and solutes movement in the soil and choosing the best management option for increasing productivity and economic performance and also reduction of nitrate pollution of soil and ground water source with the least limitations and high accuracy is necessary. The Eu-Rotate-N model has been developed for simulation of nitrogen use and specifically for optimization of nitrogen use in variation of vegetables in a wide range of conditions, which without the need to calibration has presented satisfactory results in many areas. So this study was conducted to evaluate the efficiency of Eu-Rate-N model in assessment of moisture and nitrogen distribution and yield under different nitrogen fertigation management for pepper plant. Materials and Methods: Sweet pepper was planted at density of 8.33plant per m2 in a row planting method. 150kg per hectare per year of fertilizer was used during the season. Crop yield, soil water and nitrogen content were measured on a regular basis. The treatments consisted of three fertilizer level: zero (N0), the ratio of ammonium to nitrate 20:80 (N1) and 40:60 (N2), which was conducted in a completely randomized block with three replications in Isfahan. Irrigation based on daily monitoring of humidity was used with drip irrigation system. The irrigation Depth was calculated and applied with aim of replacing the water content deficiency in the root zone up to field capacity (FC) for the no water deficit treatment. Coefficients were modified only for plant coefficients and length of each growth stage according to the area. To compare simulated data with measured data in field, indices of statistical root mean square error (RMSE), normalized root mean square error (NRMSE), coefficient of determination (r2) and index of agreement Wilmot (d) were used. Results and Discussion: The NRMSE index for nitrate and soil water content was 11.45, 12.08, the RMSE was 0.89, 0.022, the r2 was 0.998, 0.996 and the d was 0.667, 0.66 respectively. All calculated indices for soil water and nitrate content were in the acceptable range. NRMSE index was less than 20 percent in all treatments which was indicating good ability of model in simulating soil water and nitrate content and r2 was more than 90 percent which pointed out to well process of simulation of the model. The simulation accuracy was greater at the end of the growing season. Comparing of RMSE statistical index for different depths showed that the simulation accuracy was increased by increasing depth which can be due to changes in surface evaporation and also the effect of environmental factors on surficial layers more than other layers. Generally the best simulation was related to the layer of 80 to 100 cm. And the average RMSE was 0.019 cm3 per cm3 for soil moisture content and 0.22 mg per kg for soil nitrate.In the layer of 80-100 cm the best simulation of soil moisture and nitrate content between treatments was related to N0 by the RMSE equal to 0.024 cm3 per cm3 and 0.21 mg per kg respectively and the weakest simulation was related to N3.The simulated yield in all treatments was less than its actual value. Comparison of simulations between three treatments demonstrated the usefulness of EU-Rotate N to examine the effects of management on, nitrate leaching. Conclusions: The Eu-rotate-n model without calibration for site location was well capable of estimating soil water and nitrate content under different fertilizer management for Isfahan climatic conditions nevertheless it is suggested to use to calibrate yield functions to improve the yield simulation. Generally we can use Eu-rotate-n model for simulation of water and nitrogen content and eventually approach to integrated and optimal management in the farm in the hot, dry conditions of Isfahan.

Water shortage has encouraged the quest for alternative sources of water for food production and agricultural development. Recycled water (RW) is one of the most available water resources with great potential for use in farm irrigation. This experiment was carried out to investigate the use of RW as the irrigation source and its application method, subsurface leaky irrigation (SLI) system or surface irrigation, in an orchard with young olive trees in central Iran. The results revealed that the SLI system was able to enhance tree growth, leaf area, maximum fluorescence (Fv/Fm) and photosynthesis rate by 68%, 26%, 4%, and 42%, respectively. In addition, trees irrigated with the SLI system using RW exhibited increased N and Mg uptakes by 138% and 8%, respectively. Plants irrigated with RW showed a growth improvement (42%), leaf area (26%), and photosynthesis rate (23.4%) compared with those irrigated with clean water. Furthermore, Mg, Na, K, P, and N content increased by 12%, 59%, 30%, 7%, and 92%, respectively, in leaf tissue when RW was applied. The results indicated that RW could be employed as a reliable irrigation source especially when it was delivered with the SLI system.