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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.

Improving seed yield and oil quality of oilseed crops can aid in provision of a nutritious diet for humans. A worldwide collection of linseed was evaluated for seed yield (YLD), seed oil (OIL) and protein content (PRO), oil fatty acid composition, omega-3 to omega-6 ratio (ω3/ω6), total tocopherol content (TTC), and total phenolic content (TPC). At 2 years, higher temperature (~7%) and lower relative humidity (~16.6%) during the seed filling and maturity period (dryer condition) were correlated with significant decreases in YLD (~18%) and OIL (~4.5%), lower contents of linolenic acid (~13%) and TTC (9.8%), and lower ω3/ω6 ratio (~31%); oleic (~9%) and linoleic acid contents (~23%) and TPC (14.4%) increased. Correlation results demonstrated some significant associations among quantitative traits such as YLD, OIL, and thousand seed weight (TSW); however, the association of these traits with qualitative indices was mostly negative. Genotypes were classified irrespective of their geographical origin and independent of seed or flower colour. In this classification, a yellow-seeded Canadian group had the lowest ω3/ω6 ratio (~0.05), the highest seed yield and high TTC, whereas groups with the highest ω3/ω6 ratio (>3.0) had the lowest oil TTC and low to average seed yield. Results suggested that some brown-seeded Asian genotypes with high grain yield and oil potential, higher ω3/ω6 ratio, and other more stable oil quality indices are suitable to develop broadly adaptive varieties under the possible fluctuation of climatic factors. Other genetic groups could also be used for breeding programs with specific objectives.

Drought is one of the natural disasters that causes a great damage to the human life and natural ecosystems. The main differences are in the gradual effect of drought over a relatively long period; impossibility of accurately determining time of the beginning and end of drought; and geographical extent of the associated effects. On the other hand, lack of a universally accepted definition of drought has added to the complexity of this phenomenon. In the last decade, due to increasing frequency of drought in Iran and reduction of water resources, its consequences have become apparent and have caused problems for planners and managers. Therefore, in this study, to investigate severity and duration of meteorological, hydrological and agricultural drought in Karkheh River basin, regional frequency analysis of standardized precipitation index ( SPI ), standardized evapotranspiration index ( SEI ), standardized runoff index ( SRI ) and standardized soil moisture index ( SSI ) was performed using L-moments. Then, using Hosking and Wallis heterogeneity test, basin was divided into four homogeneous areas. After that, based on the Z statistic of goodness-of-fit test for each distribution, the best regional distribution function for each homogeneous region was selected. The results showed that hydrological drought occurs with a very short time delay in Karkheh River Basin after the meteorological drought and two indicators show meteorological and hydrological drought conditions well. Agricultural drought occurs after meteorological and hydrological drought, respectively, and its severity and duration are less than the other indicators. Meteorological, hydrological and agricultural droughts do not occur at the same time in all of the years and in general, the SPI drought Index shows the most severe droughts compared with the other three indices.

Thermal stress indicators are one of the most accurate indices for sensing plant water status that can be remotely measured by the means of infrared thermography. In addition to the canopy temperat...

Plant water stress can be remotely monitored by means of thermography due to its increasing effect on plant temperature. For a more accurate estimation of plant water status, its temperature should...

Creation and conservation of urban parks is challenging in arid environments where daily thermal extremes, water scarcity, air pollution and shortage of natural green spaces are more conspicuous. Water scarcity in the arid regions of Iran is major challenge for water managers. Accurate estimation of urban landscape evapotranspiration is therefore critically important for cities located in naturally dry environments, to appropriately manage irrigation practices. This study investigated two factor-based approaches, Water Use Classifications of Landscape Species (WUCOLS) and Landscape Irrigation Management Program (LIMP), to measure the water demand in a botanic garden. The irrigation water volume applied was compared with the gross water demand for the period from 2011 to 2013. On average, WUCOLS estimated an average annual irrigation need of 1164 mm which is 15% less than the applied value of 1366 mm while the LIMP estimate of 1239 mm was 9% less than the applied value. Comparison of estimated and applied irrigation showed that a water saving of 9% can be made by the LIMP method. The outcomes of this research stressed the need to modify the irrigation requirements based on effective rainfall throughout the year, rather relying on long-term average data.

This study was conducted to investigate the effects of two irrigation regimes (55 and 85% of soil available water depletion) and two nitrogen levels (0 and 112.5 kg ha−1) on yield as well a...

This study was conducted in 2015 to estimate pistachio (Pistacia vera L.) water use in Marvast region, central Iran. Daily and seasonal pistachio actual evapotranspiration (ETa) was first estimated by running the surface energy balance algorithm for land (SEBAL) model, using 12 Landsat 8 satellite images and other ancillary data. Finally, SEBAL estimates of daily and seasonal water use over three experimental sites of pistachio orchards were compared against ones based on performing water balance analysis for the top 150 cm of the soil layer. For this purpose, a simple funnel-shaped device was made and used to collect the beneath rootzone drainage water and determine the leaching fraction (LF) as well as deep percolation at three scattered points across the sub-sections of each experimental site. The results reveal that the LF varies from 0.16 to 0.34, leading to deep percolation from 95.0 to 334.0 mm of the irrigation water. Eventually, the differences between ground-based and SEBAL-based pistachio ETa were 11% (ranged from 5.7 to 14.0%) and 10% (ranged from 7.1 to 16.4%) for daily and seasonal time scales, respectively. Based on the obtained results, more than 60% of Marvast pistachio orchards have seasonal water use of 410.0 to 680.0 mm (with the average of 594.3 mm), while the cumulative ETo and cumulative pistachio ETc of the same period were 1558.0 mm and 920.0 mm, respectively. In other words, Marvast pistachio trees extract less water from the soil compared with their potential water demands. This is due to the effect of salinity on reducing evapotranspiration rate as well as deficit irrigation of pistachio trees in the water scarce area of Marvast region. In any case, the difference between pistachio ETc and ETa is reflected in declination of the pistachio yield.

The competing demands of landscape irrigation and other urban water requirements are motivating improvements in water efficiency in arid urban areas. Complex urban environments create unique microclimates that can result in different irrigation requirements across the landscape. The microclimate coefficient ( K m c ) is applied to adjust evapotranspiration from reference surfaces to local microclimatic conditions. The objectives of this study were to quantify and model urban microclimate conditions across the landscape. Air temperature and relative humidity were recorded at five landscapes with different surrounding land cover/use in the city of Isfahan, Iran, over a period of three years. The results showed that the K m c values varied both locally and over time. The monthly K m c at the five sites varied from 0.87 to 1.34. Results indicated that assuming a constant K m c throughout the year may lead to errors in estimating the water requirement of a landscape. The best regression models developed for predicting the K m c as a linear function of surface cover types explained 83 % of the variance in the K m c .

Simulation-optimization models are valuable tools for determining the optimal performance of systems. The main objective of this research was to develop and validate EDOSIM (Evaluation, Design, and Optimization of Surface Irrigation Model) as a simulation-optimization model for surface irrigation systems. For simulation, which consisted of the design or evaluation of basin, border and furrow irrigation, the Volume Balance model was used. For optimization, twenty meta-heuristic algorithms were applied. In this model, based on irrigation, the volume of infiltrated water to soil was calculated without having advance and recession data. The hydraulic objective function was used to minimize the linear combination of seven performance indicators. Regarding the optimization of the objective function, the functional, multi-dimensional, static, constraint, continuous, single-objective, and meta-heuristic optimizations were applied. Data obtained from fifteen experimental fields were used for the validation of simulation, algorithms parameters setting, and validation of optimization. Comparison of the simulation results of the EDOSIM model with those of the Hydrodynamic model of SIRMOD software showed the good performance of EDOSIM model and the proposed method for estimating the volume of infiltration with RMSE = 0.068, R2 = 0.988, CRM = 0.005 and NRMSE = 4.2%. The Shuffled Complex Evolution (SCE) algorithm was found to be the best algorithm for the optimization of fields; in all fields, the objective function was decreased (improved). Comparison of the objective function of the EDOSIM model with eight solvers of Optimization and Global Optimization Toolboxes of MATLAB software also revealed the superiority of the EDOSIM model for optimization.

Research on water stress strategies (WSS) and crop response to water stress is important to improve irrigation water productivity (WPI) and crop production especially for regions where water is a limited resource. This study was conducted to assess (i) the response of silage maize to water stress at different growth stages for contrasting water stress strategies in the semi-arid environment under pot and field experiments irrigated by a drip-tape system, (ii) to determine the relationship between applied water and total biomass (TB) in different WSS in both experiments. The hybrid 704-single-cross of maize was assessed at pot experiment during 2009 and 2010 and field experiment was conducted in 2017 under two WSS including WS1 (same irrigation event with different applied water depth) and WS2 (same applied water depth in different irrigation event) at three growth stages. Each WSS consisted of four different irrigation levels, including severe, moderate, and mild drought stress and a full irrigation. In both pot and field experiments, severe drought stress under WS1 and WS2 strategies led to a depression in LA and TB at tassel (S2) and silage harvest (S3) stages. At each growth stage, WPI values decreased with increasing water-deficit levels in both WSS’s and experiments. We found a linear relationship between TB and applied water for WS1 and WS2 in both experiments. However, the yield performance per unit of water used was higher for WS1 than for WS2. The yield response factor to stress (Ky) values for LA and TB were higher under WS2 than WS1 in both experiments, indicating that WS1 can be employed as an effective deficit irrigation management under the drip-tape irrigation system for maize in an arid area with shortage of water.

Crop models are useful tools for evaluation of management factors for any possible productivity improvement under water-deficit conditions. Such applications require an accurate simulation of the soil water balance. The main objective of this study was to evaluate the performance of CSM-CERES-Maize model for simulating soil moisture under different irrigation levels of silage-maize. This experiment was conducted in growing seasons of 2003 and 2004. Treatments were four irrigation levels (two deficit-irrigation levels at 0.7 and 0.85 soil moisture depletion (SMD), a full irrigation (SMD) and an over-irrigation treatment (1.13 SMD), indicated by W1, W2, W3 and W4, respectively). Soil moisture was measured on a daily basis in different layers of the soil profile. In the first year, gravimetric sampling method and in the second year a neutron probe were used for measuring soil moisture. Simulated soil moisture was compared with measured field values for each individual soil layer. Results indicated that root mean square error (RMSE) of the model-predicted soil moisture for different treatments, depending on depth, was 0.8–13.6%. Systematic error and the index of agreement of the model in estimating total water in 60 cm soil profile was 0.8–2.00 cm. The greatest error in estimating soil moisture always happened for top layer of the soil profile. Based on the results, it can be concluded that CSM-CERES-Maize model is able to simulate soil moisture content for wide range of soil conditions and irrigation regimes.

Knowledge about biomass partitioning of maize grown in arid and semi-arid climates is scarce and yet essential to select a robust and effective deficit irrigation management (DIM) strategy for these regions. The objectives of this study were to: i) investigate the effects of different levels of water application under two DIM strategies on the root and aboveground characteristics, the response factor to water stress (Ky) and irrigation water use efficiency (IWUE) of silage maize at different growth stages, and ii) determine the best DIM strategy that would maximize biomass productivity. Field pot experiments were conducted in Isfahan, Iran, during 2009 and 2010. The two DIM strategies were fixed irrigation interval-variable irrigation depth (M1), and variable irrigation interval-fixed irrigation depth (M2). Each DIM strategy was tested at four water-deficit levels, including: severe, moderate, mild, and a full-irrigation. In M1, irrigation intervals were consistent for all irrigation treatments but were varied over the growing season. Treatment effects were measured at the 10-leaf, 16-leaf, tasseling, milk, and silage harvest crop growth stages. There was significant effect of irrigation and growth stage on total aboveground biomass (TB), leaf area (LA), root biomass (RB), and root:shoot ratio (RSR) for both DIM strategies during the two years. For M2, there was significant difference in TB, LA, RB, and RSR between all irrigation levels at all growth stages. TB production was on the average around 25% higher for M1 compared to M2, even though total applied irrigation water was only 6% higher for M1. Comparing the two DIMs showed that RSR and Ky were both higher for M2, indicating that the crop was more sensitive to this strategy. In conclusion, M1 was selected as the best management practice since it had more favorable effects on improving the IWUE and also on the development of maize roots during the growing season.

Alfalfa (Medicago sativa L.) cultivars respond differently to drought stress levels and oxidative injury. This may provide us with an important tool to identify the chemical mechanisms operative in drought tolerant genotypes. The present experiment was conducted to determine catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POX) activities; malondialdehyde (MDA) content; herbage yield; stress susceptibility index (SSI); and drought tolerance index (DTI) of 10 alfalfa cultivars under four irrigation regimes (55, 65, 75 and 85% depletion of available soil water). Drought stress was observed to reduce herbage yield but increase CAT, APX and POX activities as well as MDA content; however, such alterations were cultivar-drought level-specific. With a few exceptions, Baghdadi had the highest CAT, POX and APX activities and lowest MDA content, lowest reduction in herbage yield and the lowest SSI and the highest DTI under all irrigation regimes suggesting that it was the most adapted and drought-tolerant cultivar. Herbage yield had a significant and positive correlation with POX and a significant and negative correlation with MDA under all irrigation regimes indicating that they could be used as markers for selecting more drought-tolerant cultivars in alfalfa. Catalase and APX also had a significant and positive correlation with herbage yield, thus they could be used as markers for selection of more drought-tolerant cultivars. The results suggested that a wide variation in drought tolerance exists within alfalfa cultivars, thus selection for more drought tolerance is possible. In addition, chemical markers such as POX, CAT and APX activities and MDA content may be used to assist in selection for more drought tolerance cultivar in this species.

Water scarcity encourages municipalities to use more precise irrigation systems in arid urban landscapes. However, major concerns are associated with the adaptation of mature trees to new irrigation systems after they have matured under traditional management. We investigated the adaptation of mature olive trees to a change in irrigation system from a traditional surface to an automatic drip irrigation system in a coarse-textured urban forest park. The growth indices of eight-year-old olive trees were monitored for the period of 2012–2014 under three irrigation systems: (1) automated drip irrigation (ADI) for trees that matured under traditional basin-surface irrigation (TSI), (2) TSI since plantation, and (3) traditional drip irrigation (TDI) irrigating the trees depending on water availability since the time of planting. We additionally determined the spatial pattern of root development by collecting 156 soil samples from each irrigation system with a 20 × 20-cm grid system (120 cm width × 80 cm depth) in the soil profile. Results showed no significant differences in terms of fruit productivity between TSI and recently established ADI systems. Automated drip irrigation resulted in the maximum root density with a uniform root distribution pattern, where roots expanded all over the soil profile. In TSI, however, the roots were distributed irregularly, with the highest density close to the irrigation basin. The wide spacing between drippers in the TDI system created large gaps between the wetted zones in the soil with a low water-holding capacity, leading to a discrete small root system. The present study highlights the positive response of mature olive trees to the replacement of the irrigation system in an urban forest park with limited available water and low soil quality. Our findings will help municipalities to properly preserve mature urban trees and the ecosystem services for their inhabitants. Non

Sunflower has become an important crop for oil production in many arid regions across the globe. However, with water as a scarce resource, efficient water and nutrient management systems need to be identified. The goal of this project was to determine the interaction between water and nitrogen (N) for sunflower grown in an arid environment. Experiments were conducted during 2010 and 2011 in an arid region in Iran that included two sunflower hybrids, four levels of surface drip irrigation, ranging from severe deficit irrigation to over irrigation, and three levels of N fertilizer, i.e. 0, 47, and 93 kg N ha−1. The treatments were arranged in a strip-plot design with complete randomized blocks with three replications. Irrigations were based on daily monitoring of soil moisture in the experimental plots. For both hybrids, irrigation and the interaction of water and N had a significant effect (P

Identification and selection of plant genotypes with survival, recovery and sustainable performance during drought periods is one of the main objectives of plant improvement for arid and semi-arid regions. This study aimed to evaluate root traits and recovery of tall fescue genotypes after a period of drought stress. A total of twenty four tall fescue genotypes were selected from a wide polycross population and assessed for field drought tolerance based on stress tolerance index (STI) and recovery during 2010–2013. The genotypes were classified as tolerant, moderately tolerant and susceptible based on STI. Then, in 2014, genotypes were assessed in a pot experiment for root characteristics under two levels of moisture environments (control and intense drought stress). In both moisture environments, root length (RL), root area (RA), root volume (RV) and root weight (RW) were negatively correlated with days to recovery (DR). Genotypes that recovered from drought had greater RL, RA, RV and RW than the genotypes unable to recover. Principle component analysis (PCA) was performed to identify genotypes with superior root characteristics, stress tolerance and recovery potential that can be used for future breeding programmes. Results indicated that selection based on combining STI, recovery and extensive root system might improve drought tolerance of tall fescue.

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.

Process-oriented crop simulation models are valuable tools for representing our understanding of the current and future states of a cropping system. The main objective of this research was to couple the Cropping System Model-(CSM)-Crop-Environment Resource Synthesis (CERES)-Maize (CSM-CERES-Maize) with the Soil, Water, Atmosphere, and Plant (SWAP) model in order to benefit from the advantages of both models. A new model was developed by replacing a simplified version of the SWAP with WatBal and SPAM modules of the Decision Support System for Agrotechnology Transfer (DSSAT) version 4.0. In this hybrid model, the CERES-Maize supplied the SWAP model with plant growth variables. Meanwhile, the SWAP model provided the CERES-Maize model with daily evapotranspiration, soil water content, and root water uptake. The model was then validated with a dataset including four irrigation levels (two deficit levels along with one full and one over-irrigation level), and three nitrogen levels (0, 150, and 200 kg/ha nitrogen) obtained from a field experiment in 2003 and 2004. The root mean square errors (RMSE) across all treatments in the simulation of final biomass were, respectively, 1175 and 2148 kg/ha in the first year and 1274 and 1514 kg/ha in the second year for the hybrid and original version of CERES-Maize model. Average RMSE for two non-water stress treatments was 1.29 and 1.35 cm in the simulation of soil water content for hybrid and original models, respectively. In general, our findings indicated that the new hybrid model was fairly successful in biomass simulation, which was due to better soil water simulations of all four irrigation levels except severe deficit irrigation.

Silicon (Si) is considered as a beneficial element to higher plants especially under stress conditions. A factorial experiment, in a completely randomized design with four replications, was used to investigate the effects of two application methods (spraying and soil drenching) and eight levels of Si compounds including 0, 5, 10 and 15 mM of potassium silicate (K2SiO3) and 0, 5, 10 and 15 mM of nanosilica (SiO2). The results indicated that Si application (all or some treatments) decreased transpiration, specific leaf area, petiole length, and promoted the flowering, fruit firmness, leaf/crown number, fresh and dry weight of shoot and root, water use efficiency. They also showed it did not affect the fruit set percentage, yield, chlorophyll index, total soluble solid, leaf area, fresh and dry weight of crown, photosynthesis, stomatal conductance, internal carbon dioxide (CO2) concentration and mesophyll efficiency of strawberry. The results suggest the beneficial effects of Si on growth and develop...

Lack of knowledge on soil geotechnical properties c an cause many problems in the construction and maintenance of irrigation and drainage networks. In general, all of unconventional soils such as gypsiferous soils can cause some problems to irrigation canals. Some studies have been conducted on a variety of problematic soils, but still there is a need for more research activities and field studies. This research was conducted to study the impact of adding perlite and pumice (5%, 10% and 15%) and micro silica (1%, 5% and 10%) on some mechanical properties of soil including shear stress, bearing capacity and Atterberg limits . Statistical analysis was done to compare their averages (P

Because of limiting water resources and increasing demand for food, it is necessary to investigate the effect of irrigation systems on water productivity. This research was conducted to evaluate yield and yield characteristics of two potato varieties under sprinkler and trickle irrigation systems. The treatments were two irrigation systems (sprinkler and trickle irrigation) and two potato varieties (Burren and Satina) in a randomized complete block design with three replications. Full irrigation was done based on moisture depletion from depth of root development in both irrigation methods.. Potato yield and water productivity (WP) in drip and sprinkler irrigation systems showed significant differences (P

SummaryTwo sources of water (clean water or recycled water) and two types of irrigation system [sub-surface leaky irrigation (SLI) or surface irrigation (SI)] were applied in a split-plot experimental design, with four replicates, to study the effects of water quality and irrigation system on the physiological behaviour and growth of olive trees (Olea europea L.) in a semi-arid region.The results showed that SLI affected not only the number of open stomata, stomatal length, rate of net photosynthesis (by 32%), leaf areas (by 21%), and stomatal conductance, but also leaf nitrogen and proline concentrations. Plants irrigated with recycled water had higher rates of photosynthesis (by 22%) and leaf areas (by 14%) compared to those given clean water. Recycled water increased the uptake of nitrogen (N) and magnesium (Mg2+) ions by 67.5% and 6.0%, respectively, which could result in higher chlorophyll concentrations, rates of photosynthesis and, eventually, enhanced plant growth. The results suggest that the use...

Genetic analysis of root and physiological traits and selection of genotypes with higher drought tolerance through these traits is generally limited in tall fescue. In this study, some parental genotypes of tall fescue first were assessed for field drought tolerance in 2014–2015 and then the polycross seeds were harvested to provide half-sib families. Sixteen half-sib families along with their corresponding parental genotypes were assessed in a pot experiment for root and physiological characteristics under three irrigation levels (control, mild and intense) in 2016. The results showed that drought stress decreased dry forage yield (DFY), relative water content and total chlorophyll and increased carotenoid and proline in both parental genotypes and half-sib families. Intense drought stress decreased most of the root traits at 0-30 cm soil depth while at 30–60 cm depth length, area, volume and dry weight of roots were increased. A broad range of general combining ability (GCA) was observed for DFY (21M and 9E), root (21M, 12L and 20L) and physiological characteristics (12L and 9E) at three irrigation levels. Moderate to high estimates of narrow sense heritability (0.40–0.72) as well as genetic variation for root and physiological traits, indicated that phenotypic selection can be successful to attain genetic progress. Indirect selection to improve DFY was more effective through selection for root and some physiological traits. Significant associations of root and some physiological traits with drought tolerance demonstrated that these traits could be used as appropriate selection criteria to elevate forage yield and identify superior genotypes for arid and semi-arid regions.

International audience; Climate change models predict more frequent and severe droughts in the world. For the future adaptation of perennial forage grasses, identification and selection of genotypes with enhanced recovery and persistence under repeated drought is crucial. The aim of the present study was to investigate traits related to persistence, recovery, and root adaptation in three sets of tall fescue genotypes with different flowering date, after successive drought stress. A total of 72 genotypes of tall fescue (24 medium, 24 late, 24 early flowering) were assessed for agro-morphological traits and persistence during 2010-2014 under two levels of soil moisture. In 2015, irrigation was withheld and all genotypes were evaluated for drought recovery in the field. Then 18 genotypes were chosen based on field results to evaluate their root traits at two irrigation levels (control and intense drought stress) in pots. In the field, plant persistence decreased from year 2 to 5 under both control and intense drought stress conditions in all three sets of genotypes, although persistence of late flowering genotypes was higher. The results also indicated that most of the genotypes with greatest persistence had higher recovery after the final severe drought. Persistence and recovery were positively correlated with root length (RL), root area (RA), root volume (RV), root weight (RW) and root to shoot ratio (R/S) under both soil moisture. Moreover, genotypes with higher recovery after drought had more RL, RA, RV and R/S than others. Application of principle component analysis to identify genotypes of interest for future breeding programs is discussed.

Knowledge of the influence of land cover on air temperature in arid cities is scarce, yet essential for urban planners to select landscape design and management strategies which can improve livability and provide efficient landscape irrigation. The objectives of this study were to consider the effects of urban land use on air temperature changes in an arid city based on data collected in Isfahan, Iran at a local scale. This study reports a statistical analysis of temperature variation with respect to land use throughout the day and night. It is also the first study to report the effects of land cover on the time that daily minimum and maximum temperature occurs. The land use characteristics considered included green space, streets, buildings, population density and bare land. Air temperature was measured for 42-months at the canopy level of five intra urban sites and one reference site in a lightly developed suburban location. The temperature of all intra-urban sites was higher than the suburban reference site for a majority of observations during daytime throughout the year. The effect of land use on air temperature overnight was greater than daytime. The highest temperature difference occurred overnight in summer, with differences up to 12 °C when comparing an irrigated, vegetated site and the suburban site on an hourly basis. On average, the daily maximum temperature in urban areas occurred sooner than in the suburb in all seasons. The highest mean time difference was 78 min between the commercial–residential and suburban stations in summer. Refereed/Peer-reviewed

Models can provide researchers with an opportunity to understand the multidimensional relationships among factors affecting crop growth. All such factors, including field condition, must be tested using models. The main objective of this study was to apply the Cropping System Model (CSM)-Crop-Environment Resource Synthesis (CERES)-Wheat model to uneven areas for simulating rainfed wheat. First, the model was calibrated at a field cultivated with wheat variety Sardari. The model was then applied to different points at a ‘hummocky’ evaluation site. At this site, 69 sample points from 5 different slope positions (summit, shoulder, backslope, footslope, and toeslope) were specified and physical and chemical soil properties as well as final grain and total aboveground wheat biomass at each of 69 points were measured. The overall results showed that the normalized root-mean-square error varied between 15% and 34% for the top weight; this was considered to be good enough for undulating areas. The model efficienc...

Research on crop response to deficit irrigation is important to reduce agricultural water use in areas where water is a limited resource. The objective of this study was to evaluate changes in physiological and root traits under mild and intense drought stress in tall fescue. It also sought to find associations between these changes and field drought tolerance. A total of 24 tall fescue genotypes were selected from a wide polycross population and assessed for field drought tolerance during 2011–2012 in the field. The genotypes were classified as tolerant, moderately tolerant, and susceptible based on drought stress tolerance index (STI), tolerance index (TOL), and yield reduction (YR). In 2013, 24 genotypes were clonally propagated and planted in polyvinylchloride (PVC) tubes under, three levels of moisture regimes. Root characteristics were investigated at 0–30 and 30–60 cm depths of soil. Also 11 physiological traits, dry forage yield, STI, TOL, and YR were recorded. At the 30–60 cm depths of soil, the root length increased by 5.95 and 7.30 % under mild and intense stress, respectively. Under mild stress, root area and root volume were positively correlated with STI. Consequences of drought stress, manifested as declined relative water content and chlorophyll, could be associated with a decrease in the activity of antioxidant enzymes. Some tall fescue genotypes had extensive root systems, high photosynthetic capacity, and less YR in the field. These genotypes may adapt to drought through drought avoidance and drought tolerance mechanisms. The application of principle component analysis for screening suitable genotypes was also discussed.

The knowledge on the relationships of protein and micronutrient concentration in wheat grain with edaphic characteristics could provide valuable information for site-specific fertilization of crops for producing grains denser in micronutrients such as iron (Fe) and zinc (Zn) in rain-fed agriculture. In this study, we used soil properties and topographic parameters in the artificial neural network (ANN) methodology as a power tool for improving models for predicting wheat grain micronutrient and protein contents in the hilly regions of western Iran. Soil and grain samples were collected from 1 m2 plots using the stratified random method, whereas the slope positions were considered as the basis of soil sampling, at 100 selected points. The mean grain Zn, Fe, Cu (copper) and Mn (manganese) concentrations were 37.02, 65.86, 14.79 and 44.93 mg–1 kg–1, respectively, and mean grain protein was 13.76%. Application of the ANN models for predicting Zn, Fe, Cu, Mn and protein contents in grains improved prediction b...

Using plant genotypes adaptable to water-deficit stress is an optimal strategy in sustainable agriculture. This study was conducted to assess the selection criteria for identifying high yielding drought-tolerant F2-derived F3 flax families from a cross between Iranian genotype KO37 and the Canadian genotype SP1066. One hundred and nineteen F2:3 lines were evaluated under drought stress and non-stress conditions using an 11 × 11 lattice design with three replications. Sixteen drought tolerance indices adjusted based on grain yield under drought stress and non-stress conditions were calculated. The presence of high variability for grain yield and irrigation water use efficiency in parental lines and F2:3 families under both conditions indicated that the F2:3 population or its advanced generations can be used in selection programs to increase drought tolerance and also to identify quantitative trait loci and genes related to grain yield and drought tolerance in flax. The results of biplots based on the PC1 a...

For evaluating the severity of drought in a certain month, two indexes of cumulative precipitation deficit (CPD) and maximum precipitation deficit (MPD) are used such that a regional frequency analysis has been carried out by L-moments. These measures of drought are strongly related to moisture deficits for the vegetation during the growing season. In this paper, 11 synoptic stations in Isfahan province, Iran, with a semiarid environment are used. The stations have a minimum of 10 years of data. The two drought indexes are calculated for all of them in whole months. The WeatherMan tool is used for completing missing data. The Food and Agriculture Organization of the United Nations Penman-Monteith (FAO-PM) method is used for calculating reference evapotranspiration [ ET(FAO-PM) ]. According to previous studies, this method is suitable for this region. The Hosking homogeneity test is applied for identifying a homogeneous region. The Hosking goodness-of-fit test is performed to select the best regional distr...

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO3) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO3-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha−1), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO3-N content of 0–30 and 30–60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO3-N leaching out of the 60-cm soil layer was 8.43 kg N ha−1, for the 142 kg N ha−1 and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO3 concentration at the 60 cm depth was 46 and 138 mg l−1, respectively. Based on our findings, it is possible to control NO3 leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.

Water scarcity and environmental pollution due to excessive nitrogen (N) applications are important environmental concerns. The Varamin region, which is located in the central part of Iran, is one of the locations where farmers apply 250–350 kg N ha−1 for silage maize without any concerns with respect to the available water for irrigation. The objective of this study was to quantify the response of the silage maize (Zea mays L.) to variable irrigation and N fertilizer applications under arid and semi-arid conditions and to determine the optimum amount of N fertilizer as a function of irrigation. The maize Hybrid 704 single-cross was planted on 3 August 2003 and on 25 June 2004. The experimental treatments consisted of three N rates (0, 150, and 200 kg N ha−1) and four levels of irrigation, including two deficit irrigation levels 0.70 SWD (soil water depletion) and 0.85 SWD, a full-irrigation level (1.0 SWD) and an over-irrigation level (1.13 SWD). Twelve treatments were arranged in a strip-plot design in a randomized complete block with three replicates. Gravimetric soil samples were collected in 2003 and a neutron probe was used in 2004 to measure soil water content. Leaf area index, total aboveground biomass (TB), plant height, stem diameter, and leaf, stem, and ear dry weight were measured during the growing seasons and at final harvest. Total aboveground biomass was affected by irrigation (P 0.5). Total aboveground biomass and biomass of the crop components increased as a function of the amount of water and N applied. For each of the irrigation levels, there was an associated optimum amount of N, which increased as the amount of irrigation water that was applied increased. Among the four irrigation levels that were studied, 0.85 SWD was the optimum level of irrigation for the conditions at the experimental site. The results also indicated that an increase in N applications is not a good strategy to compensate for a decrease of TB under drought stress conditions. We concluded that the effect of N fertilizer on TB depends on the availability of water in the soil, and that the amount of N fertilizer applied should be decreased under drought stress conditions. Further research will combine these results with a crop simulation model to help optimize nitrogen and water management for silage maize.

We examined the main and interactive effects of nitrogen (N) and deficit irrigation (DI) on the yield response factor ( K y ), water use efficiency (WUE), and irrigation water use efficiency (IWUE) of silage maize from a semiarid region of Iran. Experiments were conducted in 2003 and 2004 that included three N fertigation rates (0, 150, and 200 kg N ha −1 N0, N150, and N200, respectively) and four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil water depletion, W1, W2, W3, and W4, respectively). The soil water content measurements showed that most of the water was extracted from the top 60 cm of the soil profile. DI increased WUE for all N fertilizer treatments with the maximum value being observed at the W2 level. The average of the IWUE for the two years of the study showed that the lowest IWUE was 1.38 kg m −3 for the N0W1 treatment, while the highest IWUE was 1.8 kg m −3 for the N200W3 treatment. A linear relationship was observed between evapotranspiration and the total biomass for all N fertilizer levels in 2003 and 2004. The minimum K y to water was obtained from the N0 level as 0.64 in 2003 whereas the maximum K y was recorded from the N200 level as 0.95 in 2004. This reveals that higher N rates application would enhance corn yield sensitivity to water stress. Overall, the sensitivity of the silage maize to water stress was affected by different planting date and nitrogen fertilizer levels. We also discuss emergent trends in water and nutrient management in light of the increased need for food security in the face of changing climate and growing populations.

Development of drought-tolerant cultivars is hampered by a lack of effective selection criteria. In this research, drought tolerance of 75 genotypes of tall fescue in three sets (25 parental, 25 early, 25 late-flowering progenies) was evaluated under no soil moisture stress and soil moisture stress in the field during 2009 and 2010. Five drought-tolerance indices were calculated: stress tolerance (TOL), mean productivity (MP), geometric mean productivity (GMP), stress susceptibility index (SSI), and stress tolerance index (STI). These calculations were based on forage yield (dry matter basis) under drought (Ys) and non-drought (Yp) conditions. Soil moisture stress caused significant reduction in forage yield. Considerable genetic variation for drought tolerance was found among genotypes. A moderately high relationship was found between Yp and Ys using regression analysis, with a clear relationship in the second year. Indices GMP and STI were found to be valuable aids in the selection of drought-tolerant, high-yielding genotypes. Plots of the first and second principal components identified drought-tolerant genotypes in each set. Results indicated that selection for drought-tolerant genotypes should be planned separately for first year (establishment stage) and second year (productive stage) in tall fescue.