# Irrigation Science

Online ISSN: 1432-1319
Print ISSN: 0342-7188
Recent publications
• F. J. Villalobos
• E. Fereres
The network relations of Qanat stakeholders in Iran as an ancient type of water-supply system were considered with the aim of clarifying the societal transformation through revitalizing power dynamics. The present network was highlighted by the interaction of three groups of new actors with the greatest social power: 1. those capable of developing trust and participation ties, 2. those with high control power and high mediation who link small family groups and play a role in empowering individuals, and 3. those who have high fame and are key players by leading thoughts and resolving conflicts. Meanwhile, Boolean Combination Index confirms the increase of various quantitative indicators, such as higher reciprocity and transitivity of relationships and shorter geodetic and diameter index. This study concluded that the revival of power relations in a social–ecological system can be effective in changing the social structure based on the recognition of internal social capitals.

Collaborative implementation of agricultural yield and fertilizer input has been a fundamental issue of sustainable and green production. Aerated drip irrigation (ADI) could potentially overcome the aforementioned conflict by enhancing crop yield, quality, and water/fertilizer use efficiency in a synergistic manner. However, its effects on the accumulation and distribution of plant biomass and nutrients are still elusive. Two consecutive years of ADI experiments were conducted to investigate the effects of irrigation frequency and fertilizer amount on agronomic performance. The results indicated that watermelon yield and IWUE were increased by 7.7–52.9% and 4.7–53.5%, respectively, compared to no-aerated (CK) treatment, and that there was a positive correlation between irrigation frequency and these increases. In addition, the application of ADI and increasing the frequency of irrigation increased the total dry matter and plant nutrient (N, P, K) contents. There was no discernible difference in watermelon performance when 20% of fertilizer was reduced in ADI conditions. ADI promoted plant biomass buildup and nutrient absorption and forced nutrient partitioning from vegetative organs (root, stem, leaf) to reproductive organs (fruit), resulting in synergistic benefits in crop yield, quality, and water/fertilizer use efficiency. ADI application once every 3 days with 80% traditional fertility application was suggested as a viable regulatory method for greenhouse watermelon. Our research sheds fresh light on the putative regulatory pathway of ADI’s beneficial effects on crop agronomic performance, with potential implications for crop production strategy.

This study compares conventional drip irrigation (CDI) and partial root drying (PRD) on yield components, oil quality, and economic return of peanut crops in the 2014 and 2015 growing seasons in the Mediterranean climatic conditions of Türkiye. The main plots and subplots consisted of 3 irrigation frequencies (IF25; IF50 and IF75) and 7 irrigation levels (IL0.50=0.50, IL0.75=0.75, IL1.0=1.00, IL1.25=1.25, ILPRD50, ILPRD75, and ILPRD100). Of the subplots, 4 were CDI treatments (IL0.50=0.50, IL0.75=0.75, IL1.0=1.00, IL1.25=1.25), and 3 were PRD treatments (ILPRD50, ILPRD75, and ILPRD100). CDI treatments (IL0.50, IL0.75, IL1.0, and IL1.25) received 50, 75, 100, and 125 of Cumulative Pan Evaporation. In addition, PRD treatments (ILPRD50, ILPRD75, and ILPRD100) were considered. They received 50, 75, and 100% of IL1.0 treatment from alternate laterals, respectively. The largest and the smallest average peanut yields were obtained from the IF50IL1.25 and IF75IL0.50 treatments each year. The result showed that increasing the irrigation water amount increases the oil yield. The highest oil content, peanut yield, and generating maximum return were obtained from IF50IL1.25 in both growth years. The saturated and unsaturated fatty acid contents were remarkably infuenced by IFs and ILs. Stearic acid concentration considerably decreased under unstressed conditions, while palmitic acid values increase. The peanut quality was also afected under water stress with lower oil content. PRD has a marked efect on peanut quality under defcit irrigation of water applied with signifcantly reduced compared with DI. The high oil yield response factor (kyoil) value acquired for the peanut crop indicated its high sensitivity to irrigation interval and water defcit. It was determined that there are considerable linear relationships between the oleic acid and linoleic acid contents compared to crop evapotranspiration (ETc) during diferent irrigation intervals in each season. Economic assessment expressed that IF50IL1.25 treatment attained the highest seed and oil yield of peanuts and maximum net return in both seasons. Overall, the fndings showed that pod yield per hectare, pod weight per plant, pod number per plant, shelling percentage, palmitic and linoleic acid percentage, oil percentage, and 100-seed weight values increased with increasing irrigation water at each irrigation interval, but oleic and stearic acid percentages decreased in both years.

Elevated temperatures during berry ripening are detrimental to grape quality. The crop forcing technique (summer pruning that ‘forces’ the vine to start a new cycle) increases must acidity and malic acid concentration at harvest by delaying the date of veraison. However, little information is available on the sensitivity to water stress of forced vines. A 3-year trial was conducted to test three irrigation strategies in forced vines: a minimum threshold of mid-day stem water potential (Ψs) of −0.75 MPa before forcing (DI), a minimum Ψs threshold of −1.2 MPa only after veraison (RDI), and the combination of both treatments (DI + RDI). Results were compared to a non-forced treatment with a minimum Ψs threshold of −1.2 MPa after veraison (C-RDI). Must acidity increased, and pH decreased in the forced treatments. However, yield was reduced by 35% and irrigation requirements increased by 20% when comparing forced and unforced treatments. As a result, water use efficiency was reduced in forced treatments. Only after a dry spring did the, DI (11%) and DI + RDI (30%) treatments, save water compared to the C-RDI treatment. Moreover, although Ψs before forcing never fell below −0.75 MPa, a significant negative correlation (R² = 0.76) was found between the integral of water stress before the vines were forced and the number of forced bunches per vine. Post-veraison water stress in forced vines reduced the polyphenol content of the wine. Our findings suggest that forced vines are extremely sensitive to even mild water stress.

The presence of emitters along the lateral, as well as of connectors along the manifold, causes additional local head losses other than friction losses. An accurate estimation of local losses is of crucial importance for a correct design of microirrigation systems. This paper presents a procedure to assess local head losses caused by 6 lateral start connectors of 32- and 40-mm nominal diameter each under actual hydraulic working conditions based on artificial neural networks (ANN) and gene expression programming (GEP) modelling approaches. Different input–output combinations and data partitions were assessed to analyse the hydraulic performance of the system and the optimum training strategy of the models, respectively. The range of the head losses in the manifold (hsM) is considerable lower than in the lateral (hsL). hsM increases with the protrusion ratio (s/S). hsL does not decrease for a decreasing s/S. There is a correlation between hsL and the Reynolds number in the lateral (ReL). However, this correlation might also be dependent on the flow conditions in the manifold before the derivation. The value of the head loss component due to the protrusion might be influenced by the flow derivation. DN32 connectors and hsM present more accurate estimates. Crucial input parameters are flow velocity and protrusion ratio. The inclusion of friction head loss as input also improves the estimating accuracy of the models. The range of the indicators is considerably worse for DN40 than for DN32. The models trained with all patterns lead to more accurate estimations in connectors 7 to 12 than the models trained exclusively with DN40 patterns. On the other hand, including DN40 patterns in the training process did not involve any improvement for estimating the head losses of DN32 connectors. ANN were more accurate than GEP in DN32. In DN40 ANN were less accurate than GEP for hsM, but they were more accurate than GEP for hsL, while both presented a similar performance for hscombined. Different equations were obtained using GEP to easily estimate the two components of the local loss. The equation that should be used in practice depends on the availability of inputs.

The objective of the study is to determine the effects of root watering systems (RWS) with drip irrigation systems (DIS) and bubbler irrigation systems (BIS) on yield, water use efficiency (WUE) and fruit date palm (Phoenix dactylifera L.) quality under the different water regimes of 60, 80 and 100% of total water requirements (TWR). The experimental fieldwork was conducted during two successive seasons (2019/2020–2020/2021) in a farm at El-kharga Oasis, New Valley Governorate, Egypt. The evapotranspiration (ETo) was calculated based on the Penman–Monteith (P–M) equation from which the climatic data was retrieved from the El-kharga climatic station. The results showed that, the maximum productivity was 103 kg/tree in the second season under RWS at 100% of TWR, while, the minimum productivity was 62 kg/tree in the first season under BIS at 60% of TWR. Furthermore, the maximum WUE was 1.61 kg/m³ under RWS for 60%. The minimum WUE was 0.94 kg/m³ under BIS for 100%. The percentage of increase in WUE between the maximum and minimum values under three systems was 41.6%. The results indicated that the amounts of applied water markedly decreased in the order of RWS < DIS < BIS and increased productivity and WUE in the order of RWS > DIS > BIS. Fruit quality was significantly affected by the type of irrigation system, with the best quality obtained with the RWS followed by the DIS and then by the BIS. The RWS system, through its positive impact on water use efficiency and enhancement on fruit yield and fruit quality of date palm, seems quite suitable for the irrigation of palm trees in arid and semi-arid regions.

Improving water and fertilizer use efficiency in arid and semi-arid regions can not only promote the sustainable development of regional crop production, but also effectively meet the challenges of future global water shortage and food security. Bubbled-root irrigation is a new water-saving irrigation technology developed for arid and semi-arid areas. It not only has the characteristics of precision irrigation (improving water and fertilizer utilization and irrigation efficiency), but also has the advantage of not being easily blocked. In this study, the infiltration capacity, wetting front transport characteristics, water and nitrogen transport, and transformation characteristics of Bubbled-root Irrigation under water and fertilizer coupling conditions were investigated in the arid region of Northwest China. The results showed that under the same infiltration time, the higher the fertilizer concentration, the greater the cumulative infiltration and wetting front (horizontal, vertical upward, and vertical downward wetting front) transport distance. Based on the results, a mathematical model with cumulative infiltration or wetting front as the dependent variable, fertilizer concentration and infiltration time as independent variables was constructed. The model has high reliability (The relative deviation between the fitted value and the measured value is within ± 10%), and can be used to guide the layout of emitters in the field and crop production. Under the same infiltration time, the higher the fertilizer concentration, the higher the content of water, ammonium nitrogen, and nitrate nitrogen in the same soil node. For example, the soil water content of C = 12, 35, 60 g L⁻¹ was 8.35%, 14.37%, 23.31% higher than that of C = 0 g L⁻¹ at 10 cm horizontal and 40 cm vertical to the emitter. At the soil depth of 40 cm, the soil mass water content is 21.46%, 17.06%, 15.50%, and 10.37% at the end of irrigation and 1, 3, and 5 d of redistribution. The contents of ammonium nitrogen in soil are 228.13, 215.43, 183.16, and 116.43 mg kg⁻¹ at the end of irrigation, 3, 5, and 10 d of redistribution, respectively. Redistribution of 5–10 d, soil NH4+N\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NH}}_{4}^{+}\mathrm{N}$$\end{document} content decreased significantly. Distribution of 1–10 d, soil NO3-N\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_{3}^{-}\mathrm{N}$$\end{document} content showed varying degrees of increase. The research results are helpful to promote the application of spring root irrigation in the world, improve the utilization efficiency of water and fertilizer, and provide a new way to alleviate the pressure of water resources and food security.

The drip emitter type used influences the dissolved oxygen concentration (DOC) distribution in a drip irrigation system. Understanding the spatial and temporal DOC distribution in the irrigation system and its change pattern and determining the optimal irrigation emitter and aeration concentration threshold are important to reasonably apply aerated irrigation. Here, we designed three common drip irrigation emitter treatments under a drip irrigation system, i.e., an inserted in-line labyrinth emitter with a flow rate of 1.0 L h⁻¹ (T1) and 2.2 L h⁻¹ (T2), respectively, and a pressure-compensating emitter with a flow rate of 2.0 L h⁻¹ (T3). Each irrigation emitter was associated with five initial DOC treatments, i.e., 3–5 mg L⁻¹ (CK), 10 mg L⁻¹ (C1), 15 mg L⁻¹ (C2), 20 mg L⁻¹ (C3), and 25 mg L⁻¹ (C4). The results showed that the DOC values gradually increased in nonaerated water (CK) but gradually decreased in aerated water with standing time. Each emitter type significantly increased the DOC values after nonaerated water (CK) passed through different drip irrigation systems, and the highest increase (73.7%) was observed in the T1CK treatment. However, the DOC values significantly decreased after the aerated water passed through the drip irrigation systems, especially in the T2 treatment (33.2%). In addition, the reduction (or increase) in DOC in aerated water (or nonaerated water) in the first 10 m of the capillary pipe was smaller than that in the last 10 m for all treatments except T1C1. Furthermore, the T3 treatment had the most stable attenuation at different initial DOC treatments, with a maximum laying length of 20 m. More importantly, aeration can significantly increase DOC in the soil water (DOS), and the maximum value occurred when the initial DOC was 19.8 mg L⁻¹. Hence, for practical application, the recommended initial DOC range for aerated irrigation is 15 ~ 20 mg L⁻¹ combined with a pressure-compensating emitter at a flow rate of 2.0 L h⁻¹ (T3). This study provides technical support for the optimal design and rational application of aerated drip irrigation systems.

The aim of this study was to determine the effect of deficit irrigation on evapotranspiration, crop water productivity, irrigation water productivity, yield response, yield components and quality characteristics of grain sorghum (Sorghum bicolor L.) grown in Antalya, Turkey. The experiment was carried out in a randomized block design with three replications at four different irrigation water levels (I100, I70, I35 and I0) in two growing seasons (2019 and 2020). Deficit irrigation levels significantly decreased plant height, chlorophyll content (SPAD), stomatal conductivity, average leaf area, leaf area index, leaf weight, stem weight, panicle weight, grains per panicle and grain yield in both growing seasons. Except for the ash content in the first year, quality components such as water, oil and protein content were not significantly affected by different irrigation levels. Also, fatty acid contents were not affected by irrigation levels in both growing seasons. The correlation test revealed a strong positive relationship between leaf weight, panicle weight, plant weight and sorghum grain yield in different irrigation applications. On the other hand, there was no correlation between grain yield and different fatty acid contents. When water is not limited, it is suggested that sorghum can be irrigated by bringing soil water to the field capacity when 40–45% of the water at the effective root depth of the sorghum plant is depleted. When water is limited, timing the irrigations when 40–45% depletion in the root zone has occurred, but refilling the profile to only 70% of available water capacity is recommended to limit significant yield loss.

Efficient irrigation is critical for managing scarce water resources where precipitation is minimal. Field-scale irrigation is largely unaccounted for in landscape evapotranspiration models, primarily due to the unavailability of data and the lack of water balance components in energy balance-based evapotranspiration models. To overcome these challenges, we implemented a remote sensing-based energy and water balance model BAITSSS (Backward-Averaged Iterative Two-Source Surface temperature Solution) to calculate evapotranspiration (ET) and irrigation requirements of winter lettuce in the arid environment of the Lower Colorado River Basin. Predicted evapotranspiration and irrigation were compared against data from twelve eddy covariance (EC) sites for wide range of soil hydraulic properties operating between 2016 and 2020 and the applied irrigation, respectively. BAITSSS estimated evapotranspiration and irrigation based on vegetative formation, weather demand, soil hydraulic characteristics, and predefined management allowed depletion (MAD) (0.4–0.6). Ground-based weather data, Sentinel-2-based vegetation indices, and SSURGO (NRCS soil survey database) soil moisture characteristics were model inputs. The results showed mean seasonal ET from BAITSSS and EC were comparable, differing on average by about 7% based on a constant rooting depth (500 mm) and MAD of 0.5 for entire crop growth stages. Variations in daily and seasonal ET were mainly due to differences in applied and model-simulated irrigation. Seasonal values of applied and simulated irrigation closely agreed (~ 6%) in most sites, though some sites applied irrigation more effectively than others. Overall, this study provided insight into consumptive water use and field-scale irrigation practices, as well as the capabilities and limitations of model-simulated ET and irrigation.

Fresh water shortages are severally restricting sustainable agriculture development in coastal saline-alkali land in Hebei Province, China. Saline water used for irrigation can increase crop yields as well as the risk of soil salinization. To identify safe and simple ways of using saline water in this region, a continuous two growth period of winter wheat field study was conducted from 2016 to 2018 to evaluate the effect of saline water irrigation on soil salt and winter wheat yield under a subsurface drainage system. This study comprised three treatments (non-irrigation, freshwater irrigation, and 6 g/L saline water irrigation), with winter wheat irrigated at the jointing-heading stage. The results indicated that the yield of winter wheat under the irrigation treatment was more than 1.5 times than that of rainfed winter wheat, and there was no significant difference between the yield under freshwater and saline water irrigation. The soil salt content decreased yearly after saline irrigation treatments. Based on subsurface drainage system, two consecutive years of saline water irrigation would not cause salt accumulation in the soil, and has increased winter wheat yield. This makes safe utilization of saline water resources realized. Saline water irrigation is equivalent to an increase of 600 m3 of irrigation water resources per hectare. The results provided scientific basis for the safe utilization of saline water resources, grain yield guarantee, and soil sustainable development in coastal area of Hebei Province.

The estimation of irrigation water requirements (IWR) amount and timing is crucial for designing water management strategies at the regional scale. Irrigation requirements can be estimated with different types of models: very complex and detailed crop models, agent-based models, or simplified modeling approaches. Because simplified approaches are often preferred, in this study, we evaluate the consequences of using simplified approaches for IWR assessment at a catchment scale and the consequences of various modeling choices, providing information on the uncertainties. To this end, different simple modeling approaches based on the CropWat model are compared with an agent-based approach (MAELIA), which serves as a benchmark. To assess simulations in detail, partial variance is calculated for several indicators characterizing daily simulated irrigation. Our sensitivity analysis, applied over a sub-catchment of the Aveyron River (southwestern France), shows a high variability in simulations produced by CropWat between the modeling assumptions tested, principally explained by the rules for irrigation triggering and the quantification of daily irrigation. The analysis also shows that several simplified approaches are able to reproduce the irrigation simulated by the high-accuracy MAELIA model, but not necessarily corresponding to an optimal irrigation scheme. Hence, this study confirms the possibility of assessing daily irrigation with simplified approaches, but warns about high modeling uncertainties, reflecting uncertainty in effective irrigation practices. This uncertainty can be taken into account by water managers and modelers through the combination of a set of irrigation models.

In recent decades, worldwide wine-growing regions have been affected by increasingly more frequent effects of climate change, such as long period of droughts during the growing season, summer heat waves, and late spring frost events, thus causing concern for the grape quality and production. In this context, it is necessary to develop innovative agronomic practices to counter the various negative effects from those extreme weather events, by equipping the vineyards with effective and reliable multifunctional systems, which are also economically sustainable. Particularly, a multifunctional irrigation system can be used to reduce the risk of extreme weather events and, at the same time, to improve quality and quantity of grape production, reducing their inter-annual variability as well, by providing an optimized plant water nutrition. In a vineyard situated south of Lake Garda (Northern Italy), a multifunctional irrigation system equipped with drippers and mini-sprinklers (the latter to protect from both late spring frost and summer high-temperature event) was assessed. The results obtained for the growing season 2020–21 showed that the optimized drip irrigation reduced water consumption without affecting the grape yield, both in quantity and quality. The frost protection operated by mini-sprinklers increased the air temperature at bud’s level of about 1 °C, suggesting a positive effect on plant production. Finally, in 2020, must quality was positively affected by summer sprinkler irrigation, increasing the levels of malic acid and titratable acidity of over 0.7 g L ⁻¹ while lowered total soluble solids. Further activities in the 2022 season intend to better assess the water use efficiency of this promising multifunctional system.

Forage cactus is an important crop for feeding ruminants in the dry regions of the globe. However, elevated rates of soil salin-ity and evapotranspiration can reduce or limit the growth of these plants. This study aimed to evaluate the effects of different levels of saline water (0.1; 2.5; 5.0; 7.5 and 10.0 dS.m −1) applied via irrigation, and the use of mulch cover (rice husk) on the morphophysiological and productivity traits of the forage cactus Nopalea cochenillifera (L.) Salm-Dyck, during a 2-year field trial. The experiment was randomized in blocks, in strip-plot, with four replications. Dry matter yield (DMY), water use efficiency (WUE), and cladode thickness showed a negative response to the higher salt concentrations in water, during the first year of cultivation, but with no effects in the second year (mean DMY of 7 Mg ha −1 year −1). Soil cover with rice husk promoted a greater number of cladodes per plant (10 units), thicker cladodes (2.1 cm), superior cladode area (323 cm 2), and lower dry matter content (78 g kg −1). Saline water up to 10.0 dS.m −1 can be used in the irrigation of Nopalea cochenillifera (L.) Salm-Dyck, since water supplementation is enough, combined with good soil drainage and well-established plantations.

One important problem in implementing a closed-loop irrigation system is the determination of the optimal locations to install the sensors, both vertically and horizontally, such that improved pressure head estimation can be obtained. In this work, we find the best locations of the sensors in terms of degree of observability in an actual field and investigate whether the optimal sensor placement can significantly improve the pressure head estimation performance in actual applications. We investigate the impact of sensor placement in pressure head estimation for an actual agricultural field in Lethbridge, Alberta, Canada. In an experiment on the studied field, 42 watermark sensors were installed at different depths to collect the soil water tension measurements. A three-dimensional agro-hydrological model with heterogeneous soil parameters of the studied field is set up. The modal degree of observability is applied to the three-dimensional system to determine the optimal sensor locations. The extended Kalman filter (EKF) is chosen as the data assimilation tool to estimate the pressure head of the studied field. Pressure head estimation results for different scenarios are obtained and analyzed to investigate the effects of sensor placement on the performance of pressure head estimation in the actual applications. Estimation results indicate that optimally placed sensors reduce the average root mean square error by about 30% compared to the case the sensor positions are selected randomly.

Water scarcity is a major constraint to citrus production in tropical regions. Proper irrigation scheduling using efficient irrigation methods such as microirrigation systems is a key to sustainable citriculture. In recent years, plant-based measurements have emerged as potential methods for irrigation management in crops. Infrared thermometry (IT) is one of the modern tools to monitor plant water stress. Crop water stress index (CWSI) computed using plant foliage temperature measured by IT has been considered as a potential index for irrigation scheduling. The present study was conducted to evaluate the effects of CWSI-based drip irrigation scheduling on water use, plant water status, fruit yield and quality and water productivity of citrus in central India. Differential irrigation was scheduled at CWSI of 0.6, 0.4 and 0.2 in combination with 40% crop evapotranspiration (ETc), 60% ETc and 80% ETc, respectively, and compared with alternate day full irrigation (FI, 100% ET) using drip irrigation system. The fruit yield in irrigation at CWSI 0.4 + 60% ETc was at par with that at CWSI 0.2 + 80% ETc and FI. However, 40% water saving resulted in 74% higher water productivity in irrigation at CWSI 0.4 + 60% ETc compared with FI. The fruits under CWSI 0.4 + 60% ETc had superior qualities (high fruit weight, total soluble solids and lower acidity) than FI fruits. Plant canopy volume (PCV) was highly correlated (R2 = 0.89) with crop water use. Overall, the study reveals that irrigation at CWSI 0.4 + 60% ETc could improve the water productivity and fruit quality with substantial water saving in citrus production in water scarce region.

Because of an increased incidence of drought, irrigation has become an important agricultural practice in formerly mesic regions. Efficient irrigation scheduling depends on a good knowledge of tree water relations. For three growing seasons, we monitored stem water potential (Ψstem) in two apple tree cultivars (Malus × domestica cv. ‘Red Jonaprince’ and ‘Gala Brookfield’) with and without irrigation. We also determined xylem potentials at 12% and 50% percent loss of conductivity (Ψ12, Ψ50) and vessel diameters in current-year shoots. To evaluate if trees are capable of osmotic adjustment, we measured turgor loss point (TLP), osmotic potential at full turgor, and the concentrations of organic osmolytes (proline, glucose, sucrose, and sorbitol) in leaves throughout the growing season. We found that Ψstem did not drop below − 1.6 MPa, which is well above the Ψ50 and TLP. Irrigated trees (ETc-100) had slightly higher Ψstem than trees without irrigation (ETc-0). The observed conditions in one of the 3 years resulted in similar yields but smaller fruit sizes of the non-irrigated trees. The triploid cultivar ‘Red Jonaprince’ had typically more negative Ψstem than the diploid cultivar ‘Gala Brookfield’, but ‘Gala Brookfield’ exhibited higher limitations in fruit growth during drought and shoot growth during wet periods. Concentrations of all measured osmolytes were higher in leaves of non-irrigated trees of ‘Gala Brookfield’ and increased during the season, while the pattern was more variable in ‘Red Jonaprince’. In summary, our results indicate that ‘Red Jonaprince’ favours hydraulic efficiency against safety, while ‘Gala Brookfield’ adopts a more conservative growth strategy.

Soil salinity and associated problems are the major challenge for the arid region of Northwest China. Strategies to cope with salinity, including a better understanding of the impacts of soil salinity on the crop coefficient (Kc), are essential for precision irrigation in arid regions. In this study, two years of non-weighing lysimeter (NWL) experiments were conducted to investigate the Kc of cotton (Gossypium hirsutum L.) under different degrees of soil salinization. The stress coefficient (Ks) model was modified and validated based on the NWL and field experiments. Three irrigation water qualities (GW, groundwater, 1.27 g l⁻¹; BW, brackish water, 3.03 g l⁻¹; SW, saline water, 4.90 g l⁻¹) were applied to mulched-drip irrigated cotton. Both NWL and field experiments revealed that BW and SW irrigation increased the soil salt content which reached the moderately saline soil level. Adjusted for local weather, the Kc-Local of cotton for the initial, middle and end seasons was 0.29, 1.10 and 0.52 under slightly saline soil (GW irrigation) and 0.24, 0.98 and 0.46 under moderately saline soil (BW and SW irrigation). In addition, the linear negative correlation relationships of soil ECe with yield response factor (Ky) and slope b (reduction in yield per increase in ECe beyond the ECe threshold) were developed. Furthermore, the Ks model was modified under salt stress conditions, which provided an acceptable Ks estimation under field conditions. These findings could be helpful for efficient water management in cotton cropping systems under mulched drip irrigation in arid regions.

We conducted this study considering the global greenhouse effect and world food security to determine a water-saving planting pattern that results in fewer carbon emissions and stable crop yields in the North China Plain (NCP). From 2015 to 2019, we conducted a two-factor winter wheat experiment composed of four treatments, with planting patterns (W, wide-precision planting pattern; and C, conventional planting) as the primary factor and different irrigation timing (I1, 60 mm irrigation at the jointing stage; and I2, 60 mm irrigation 10 days after the jointing stage) as the secondary factor. The treatments were as follows: WI1, WI2, CI1, and CI2. The soil respiration rate, soil carbon emissions, grain yield, and carbon emissions efficiency (CEE) were measured for each treatment. The W treatment resulted in a lower soil respiration rate and reduced soil carbon emissions. The W and I2 treatments resulted in significantly increased grain yields and reduced soil carbon emissions compared to the C and I1 treatments, respectively. The CEE of the WI2 treatment was higher than that of the other treatments. This study demonstrated that the combination of the W planting pattern and delayed irrigation 10 days after the jointing stage was effective in reducing soil carbon emissions while ensuring a stable grain yield in the NCP. The results of this study provide practical evidence for the sustainable development of winter wheat in the NCP. The combination of the W planting pattern and delayed irrigation 10 days after the jointing stage is an agronomic technique worth popularizing.

The paper studies the application of mathematical modelling of moisture transport as a tool for assessing the accuracy of measurements in the process of drip irrigation management in production conditions. We propose a novel modelling framework aimed at solving the problem of automated detection and correction of measurement inaccuracies, which can be implemented in decision support systems in irrigation. At first, the problem of predicting the dynamics of soil moisture content is studied on the base of the two-dimensional Richards’ equation stated in terms of water head. The values of model’s parameters are identified using the particle swarm optimization algorithm. The ability to assess the reliability and accuracy of measurements was tested by studying deviations of the simulated values from Watermark sensor readings along with the variations within the growing season and between several seasons of identified values of model’s parameters that can serve as indirect indicators of changes in soil structure. The results of computational experiments prove the stability of the considered technique to the amount of initial data and to the level of potential errors, and the ability to identify and correct errors of soil moisture measurements in the conditions of drip irrigation.

To achieve Goal 6 of the 2030 Agenda for Sustainable Development and provide water for all, water reuse is essential. We assessed the potential of treating greywater (LGw) while reusing it via irrigation of Canna x generalis, commonly used in nature-based solutions (NBS), with a view on plant development. The study was conducted at a mesocosm scale with factorial designs to test two substrates and four types of irrigation water. Stage 1 tested LGw, LGw with nutrients (LGw + N), tap water (TW) and TW + N. Stage 2 tested indoor and outdoor applications of TW (TWi and TWo, respectively) and LGw (LGwi and LGwo, respectively). All treatments resulted in reductions in total nitrogen and phosphate concentrations. The effluent turbidity, chemical oxygen demand, and surfactant contents of LGw + N and LGw decreased considerably after passing through the substrate. The results showed no statistical differences among the measured variables when LGw and TW received commercial fertilizers, which provided advantageous conditions for complete plant development, as evidenced by flowering. Conversely, compared with all other treatments, LGw treatment alone resulted in inferior development and exhibited some symptoms of nutritional deficiency, observed as reductions in dry biomass in the aboveground parts (range: 1.87–6.52 g) and belowground parts (10.03–36.19 g). Overall, Canna x generalis did not exhibit symptoms of toxicity and became fully developed, except for flowering, proving to be a robust species that is resistant to adverse environmental conditions, and is therefore recommended for cultivation in nature-based systems for landscaping integrated with LGw treatment and reuse.

The aim of this study was to determine the effect of deficit irrigation applications at different levels on cool-season and warm-season turf irrigated by a sprinkler irrigation method. Field experiments were conducted in Istanbul, Turkey (41°03ʹN; 28°00ʹE; 46 m above sea level) during the growing season of 2019. In the study, two different turf types: a cool-season turfgrass mixture (C) and a warm-season turfgrass or Bermudagrass (W) were subjected to three different irrigation levels (I1: Full irrigation, I2: 1/3 deficiency, I3: 2/3 deficiency) and examined in split-plots via a randomized complete block design conducted in triplicate. The soil moisture level was monitored via time-domain reflectometry (TDR) each day to provide irrigation timing. Unfortunately, none of the treatments were adequate to keep cool-season turf green after July because of a high MAD (Management Allowable Deficit) value. In the first 3-month period (May to July) of the experiment, during which both types of turf could survive, the seasonal evapotranspiration and the total amount of irrigation water applied were 11% more for the cool-season turf than for the warm-season turf. In the warm-season turf, although all irrigation levels provided for plant survival, the I2 treatment is suggested when all quality parameters, such as the amount of irrigation water applied, the water used, the irrigation water-use efficiency and the quality parameters are evaluated together. Seasonal average values for Crop Water Stress Index (CWSI) were calculated for the different irrigation treatments ranging from 0.57 to 0.66 for cool-season turf and from 0.52 to 0.66 for warm-season turf. The average CWSI values before irrigation was applied were from 0.68 to 0.79 for cool-season turf and from 0.69 to 0.79 for warm-season turf. The Jensen-Haise method (JH) was chosen as the best equation when reference evapotranspiration estimation methods were compared for both types of turf.

The present study proposes and evaluates an integrated optimization framework for agricultural planning in which an environmental flow model, drought analysis, cropping pattern model, and deficit irrigation functions are linked. Fuzzy physical habitat simulation was used to assess the environmental flow regime. A regression model was applied to develop the deficit irrigation functions. Average river flow time series in three hydrological conditions (dry, normal, and wet) were obtained using drought analysis. The environmental flow model, cropping pattern model, deficitirrigation functions, and river flow time series were then used in the structure of the optimization model. The goal of the optimization model is to provide an agricultural plan, including optimal cropping patterns and irrigation supply that minimizes ecological impacts on the river ecosystem. A genetic algorithm was used in the optimization process. Based on case study results, the proposed model is able to minimize ecological impacts on the river ecosystem in all hydrological conditions and propose an optimal plan for cropping patterns and irrigation supply. The difference between average revenue in the optimal plan and current conditions in all simulated hydrological conditions is less than 10%, which means the optimization system provides a sustainable plan for agricultural and environmental management.

The present study proposes and evaluates an integrated optimization framework for agricultural planning in which an environmental flow model, drought analysis, cropping pattern model, and deficit irrigation functions are linked. Fuzzy physical habitat simulation was used to assess the environmental flow regime. A regression model was applied to develop the deficit irrigation functions. Average river flow time series in three hydrological conditions (dry, normal, and wet) were obtained using drought analysis. The environmental flow model, cropping pattern model, deficit irrigation functions, and river flow time series were then used in the structure of the optimization model. The goal of the optimization model is to provide an agricultural plan, including optimal cropping patterns and irrigation supply, that minimizes ecological impacts on the river ecosystem. A genetic algorithm was used in the optimization process. Based on case study results, the proposed model is able to minimize ecological impacts on the river ecosystem in all hydrological conditions and propose an optimal plan for cropping patterns and irrigation supply. The difference between average revenue in the optimal plan and current conditions in all simulated hydrological conditions is less than 10%, which means the optimization system provides a sustainable plan for agricultural and environmental management.

Plant interception significantly affects canopy-related eco-hydrological processes (evapotranspiration, transpiration, and soil water intake) and the development of precise irrigation schedules. In maize plants, the motion of sprinkler water droplets on leaves under different irrigation conditions influences the canopy interception mechanism. In this study, indoor experiments were performed to evaluate the interception capacity of maize plants under varying sprinkler irrigation conditions at different plant growth stages using sprinkler intensity and droplet diameter as independent variables. A water balance method was used to calculate the interception losses at different growth stages of maize plants under different sprinkler irrigation conditions. Predictive models for interception were developed based on the relationships between the physical parameters of sprinkler water and the plant morphological parameters with the interception amount. Results showed that during the growing season, the mean values of the interception amount and rate of maize plants were 2.31 mm and 13.47%, respectively. The interception amount and rates of sprinkler water by the plants varied with plant growth. Furthermore, the greater the sprinkler intensity and the smaller the droplet size, the greater the canopy interception. Compared with other morphological parameters of the plants, the effects of plant surface area on interception were highly apparent, and plant surface area was selected to characterize the morphological characteristics of the whole plant as it pertained to interception. In addition, we developed ‘interception amount versus plant surface area’ power function regression models with high prediction accuracy based on different sprinkler intensities and droplet diameters. The research findings hold value as references in guiding the development of precise sprinkler irrigation schedules with optimized physical characteristics, thereby improving the practical usage of sprinkler irrigation water.

Precision irrigation can affect orchard water status and water productivity (WP). It is hypothesized that crop water status-based irrigation at the subfield scale can maintain tree water status according to targets, thereby increasing WP. Our objectives were to define a spatiotemporal decision support protocol for variable rate drip irrigation (SDSP-VRDI) in a well-watered peach orchard and to evaluate protocol efficiency on a subfield scale. Research was initiated during 2017 in a uniformly irrigated commercial peach orchard. In 2018, half the orchard was converted to SDSP-VRDI utilizing a model developed to study the relationship between stem water potential (SWP) and thermal image-based crop water stress index (CWSI). In 2019, the orchard's south subplot continued to be irrigated uniformly while its north subplot was managed according to SDSP-VRDI during the primary stage of fruit growth and the period of peak irrigation (stage III). The SDSP-VRDI included seven steps including calculation of the CWSI per management cell (MC) using thermal imagery. The CWSI was used to estimate SWP that was compared to a specified target range driving irrigation applied per MC based on FAO-56. The target range was reached in most MCs by applying MC-specific irrigation. Some specific MCs responded well to higher amounts of irrigation while others did not, as evident from relative yield, WP, and water cost efficiency data. Management downscaling from field to subfield scale appears to be beneficial and could advance precision irrigation management of complex orchard systems.

Sustainability in irrigation has become a major concern as water scarcity threatens sustainable development. In the present study, an Irrigation Sustainability Index (ISI) has been developed and proposed for application in agricultural basins. The ISI uses indicators of four dimensions of sustainability: economic, social, institutional, and environmental, and it was tested in the Segura River Basin in southeastern Spain. The results evidence the (un)sustainability of the system in 17 out of the 62 irrigation districts in the Segura Basin, mainly due to farmers’ low income, the overexploitation of aquifers, and the high demand for water for crops. On the other hand, 45 out of 62 irrigation districts showed moderate and high irrigation sustainability, mostly located along the Segura River and other streams, in the so-called “traditional agroecosystems”. The index application evidenced the prioritization of economic over environmental aspects and generated data to develop future policies in the region.

Indian pennywort (Centella asiatica (L.) Urban) is an important herbal plant with valuable medicinal properties. Irrigation with optimum freshwater is a basic crop requirement for plant growth, development, and secondary metabolite enrichment. The objective of the study was to evaluate the effect of different irrigation regimes on plant morphological, physiological, and biochemical responses as well as total centelloside content. Leaf greenness (SPAD), maximum quantum yield of PSII (F v /F m), and photon yield of PSII (Φ PSII) in plants grown under 64% field capacity (FC) were significantly reduced by 31.60%, 7.65%, and 25.91%, respectively, compared with plants grown under well irrigation (control; 100% FC). Remarkably, net photosyn-thetic rate (P n), stomatal conductance (g s), and transpiration rate (T r) in plants grown under 64% FC were more sensitive to water shortage, leading to a decline by 68.76%, 87.50%, and 84.08%, respectively, over the control. Leaf temperature (T leaf) and crop water stress index (CWSI) under limited irrigation conditions (64% FC) were, respectively, increased by + 3.97 °C and 0.72 over the control in relation to decreased T r (0.43 mmol H 2 O m −2 s −1) and altered stomatal functions indicated by low g s (0.02 mmol H 2 O m −2 s −1). Enhancement of glucose (2.70-fold over the control), fructose (2.14-fold over the control), and total soluble sugar (2.52-fold over the control) played a key role in osmotic adjustment when plants were exposed to moderate irrigation conditions (75% FC). Asiaticoside, asiatic acid, and total centellosides in the leaf tissues were enriched under limited irrigation conditions than those in the control, leading to the maximum centellosides yield at 75% FC. Number of green leaves, leaf area, stolon length, and shoot fresh weight in moderately irrigated plants (75% FC) were increased by 1.23, 1.24, 1.13, and 1.15-folds, respectively, over the control. The basic information obtained from this investigation provides a better understanding of the response of Indian pennywort under limited irrigation schedule and suggests an alternative way to manipulate biomass production and yield of total centellosides using moderate level of irrigation (75% FC).

Accurate estimations of actual crop evapotranspiration are of utmost importance to evaluate crop water requirements and to optimize water use efficiency. At this aim, coupling simple agro-hydrological models, such as the well-known FAO-56 model, with remote observations of the land surface could represent an easy-to-use tool to identify biophysical parameters of vegetation, such as the crop coefficient Kc under the actual field conditions and to estimate actual crop evapotranspiration. This paper intends, therefore, to propose an operational procedure to evaluate the spatio-temporal variability of Kc in a citrus orchard characterized by the sporadic presence of ground weeds, based on micro-meteorological measurements collected on-ground and vegetation indices (VIs) retrieved by the Sentinel-2 sensors. A non-linear Kc(VIs) relationship was identified after assuming that the sum of two VIs, such as the normalized difference vegetation index, NDVI, and the normalized difference water index, NDWI, is suitable to represent the spatio-temporal dynamics of the investigated environment, characterized by sparse vegetation and the sporadic presence of spontaneous but transpiring soil weeds, typical of winter seasons and/or periods following events wetting the soil surface. The Kc values obtained in each cell of the Sentinel-2 grid (10 m) were then used as input of the spatially distributed FAO-56 model to estimate the variability of actual evapotranspiration (ETa) and the other terms of water balance. The performance of the proposed procedure was finally evaluated by comparing the estimated average soil water content and actual crop evapotranspiration with the corresponding ones measured on-ground. The application of the FAO-56 model indicated that the estimated ETa were characterized by root-mean-square-error, RMSE, and mean bias-error, MBE, of 0.48 and -0.13 mm d⁻¹ respectively, while the estimated soil water contents, SWC, were characterized by RMSE equal to 0.01 cm³ cm⁻³ and the absence of bias, then confirming that the suggested procedure can produce highly accurate results in terms of dynamics of soil water content and actual crop evapotranspiration under the investigated field conditions.

Transport of aerosols resulting from sprinkler irrigation of treated wastewater is a complex phenomenon due to the combined effect of several parameters including fine droplets (<0.15 mm) and wind speed, which are the most important vectors for pathogen transmission. The objectives of the present study were (1) to characterize the distribution of the fine droplet plume emanating from a sprinkler head in the horizontal and vertical axes under different meteorological conditions and (2) to model (i) the short-range airborne transport and (ii) sedimented transport based on the combination of meteorological and spatial parameters. Nine experiments have been conducted outdoor under different environmental conditions. By injecting a fluorescent dye (Acid Brilliant Flavine) into the water, the distribution of aerosols emanating from an impact sprinkler under 350 kPa operating pressure was measured vertically (1–10 m above the ground) downwind and horizontally within a perimeter equivalent to 4 times the sprinkler range (20–40 m). Crosswind distribution of the droplet plume from a sprinkler was found to be Gaussian, and its dispersion rate depended on wind speed and the standard deviation of the wind direction. From the distance of 20–40 m from the sprinkler head, and 1 m above the ground, airborne transport fell from 20.8 and 3.43 mL m⁻² h⁻¹ to below 2.89 and 0.13 mL m⁻² h⁻¹ for wind speeds of 3.6 and 1.1 m s⁻¹, respectively. Moreover, different models have been evaluated by varying the factors considered. It was found that two empirical models, which combine spatial variables, and the key meteorological parameters, including wind speed, the standard deviation of wind direction, temperature, and relative humidity (for airborne transport), provide the best correlations between the simulated transport values and the observed data (R² = 0.9). Therefore, these models can be used for future studies to evaluate the risks linked to treated wastewater reuse for irrigation.

Recent economic, environmental, and regulative concerns force farmers to precise their fertilization practices. Yet, a critical knowledge gap concerning the temporal variability in perennials’ nutritional requirements renders most fertilization applications inefficient. While mass balance studies could illustrate the dynamics of crops’ mineral uptake, their association to field conditions remains a challenge. Hence, we constructed an empirical framework to convert data from lysimeter studies to applicable farming information. We fitted quadratic equations to the correlations between irrigation and drainage mineral concentrations of three perennial crops—almond, avocado, and pomegranate. Then, we derived the optimal irrigation mineral composition by the interpolation point of the nitrogen, phosphorus, and potassium curves. We also matched polynomials to the relations between leaf mineral concentrations and fertilization compositions and established mineral diagnostic references for each sampling period. Repeated measures of the crops’ response curves illustrated a temporal variability in their nutrient uptake, highlighting that the evergreen avocado extracts nutrients throughout winter, early blooming almond extracts nutrients in spring, and late fruiting pomegranates obtain minerals throughout summer. Moreover, the deciduous almond and pomegranate require extensive summer fertilization for the following spring's bloom. Recurrent leaf diagnosis exhibited that almond leave’s optimal nitrogen concentrations drop by midsummer. Optimal phosphorus concentrations in avocado and pomegranates doubled during summer, as did the optimal potassium concentration in pomegranates’ leaves. Accordingly, we established an empirical approach to process data from lysimeter studies and constructed specific fertigation assays for almond, avocado, and pomegranate trees.

Cascade rice flood distribution (CASC), the predominate method used for rice irrigation in the lower Mississippi River basin (LMRB), is inherently water intensive owing to the need to overfill rice paddies to move irrigation water from one paddy to the next. The objectives of this research were to devise practices that make CASC more water efficient, assessing how early cascade rice irrigation shutoff (ECIS) impacts applied irrigation, run-off, and flood depth under LMRB rainfall conditions. This research used a conservation-of-mass model to show that using flood depth in the penultimate rice paddy to trigger irrigation shutoff in a 16-ha simulated rice field results in nominal irrigation water savings of 23% relative to CASC. This savings was reduced to 15% when supplemental irrigation was added to the last paddy at two critical stages of rice production. Field run-off estimates for ECIS were reduced by up to 78% relative to a CASC for both clay and silt loam soils, demonstrating how with ECIS the last paddy of a rice field acts as a ‘catch basin’ for excess up-field irrigation and uncaptured rainfall. Flood depth estimates for the last paddy resulting from ECIS resembled those of alternate wetting and drying flood management (AWD), suggesting that the agronomics developed for AWD could be used to help address production issues arising in the catch basin from ECIS. Success in coupling ECIS with irrigation automation technologies could reduce aquifer withdrawals across the rice producing areas of the LMRB.

Accurate measurement of soil wetting pattern from the point source of drip irrigation system plays an important role for designing of the irrigation system. The study evaluated a novel empirical method for predicting soil wetted dimensions surrounding a drip emitter. The study conducted at Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar, in a high-density apple orchard during 2018–2020. The feld data were used to evaluate the fve diferent semi-empirical models, namely, Al-Ogaidi (A-O), Malek and Peters (M–P), Amin and Ekhmaj (A–E), Jiusheng Li (J-L) and Schwartzman and Zur (S–Z). The model’s results were compared with feld data for predicting the wetted pattern. The soil wetting front was measured using three diferent capacity emitters (2, 4, 8 lph) under a point source of a drip irrigation system. The results were evaluated on the basis of statistical comparisons [mean absolute error (MAE), root mean square error (RMSE), Nash–Sutclife efciency (NSE) and coefcient of determination (R2)] between model-predicted and feldobserved data. The newly developed empirical model has shown close agreement as compared to other models with MAE, RMSE, NSE and R2 for wetted soil width 0.205 (cm), 0.246 (cm), 0.996 and 0.997, respectively, and for wetted soil depth 0.421 (cm), 0.522 (cm), 0.992 and 0.993, respectively. The developed model accurately predicts the whole wetting pattern and performs well in reproducing from known experimental data. The study revealed that the higher the emitter discharge capacity, the more were the vertical soil wetting front advances with increased time duration of irrigation. The information of accurate wetting pattern of drip from a point source will be useful for the optimal design of drip irrigation systems.

The microorganisms in the water sources are closely related to drip irrigation emitter clogging and clogging substances accumulation. However, few studies quantitatively considered the role of microorganisms in the emitter clogging process, especially in the high-sediment water source. The coupling process and mechanism between solid particles and microorganisms are not clear yet. Based on these, the Yellow River water (CK), general high sediment water (GHS) and artificial simulated Yellow River water (SYR) was applied in an indoor controllable experiment to study the long-term dynamic drip irrigation emitter clogging process, microorganism growth and its secretions as well as clogging substances accumulation. The results showed that the presence of microorganisms could accelerate the clogging process, with smaller discharge ratio variation (Dra) and Christiansen coefficient of uniformity (CU), and higher accumulation of clogging substances. Among them, the Dra and CU of the SYR treatment were the smallest at the end of the experiment (14.7% and 30.5%, respectively) and those of the GHS treatment were the largest (21.2% and 33.9%, respectively). Meanwhile, the total amounts of phospholipid fatty acids (PLFAs), extracellular polymer substances (EPS) and dry weight (DW) in SYR treatment were the highest, which were 110.2%, 23.8% and 16.7% higher than those in GHS treatment, respectively. The clogging parameters and clogging substances accumulated from the CK treatment were in a state of in-betweenness. However, the differences between CK and SYR treatments did not reach a significant level, while they were both significantly different from GHS treatment (p < 0.05). This mainly resulted from the interactions between solid particles and microorganisms in the drip irrigation emitter clogging process. Ignoring the existence of microorganisms may overestimate the Dra and CU by 6.5% and 3.4%, respectively. This offered theoretical references to the application of high-sediment water in the drip irrigation system.

Because of the presence of shallow water tables and consequent secondary salinization in irrigated areas of Xinjiang China, there is an urgent need for installation of drainage systems to control the salinity levels in the crop rootzone. The goal of this study was to compare the midterm effects of the open ditch (depth of 2.2 m) and subsurface pipe (depth of 2.2 m) drainages on soil salinity, drainage, groundwater, cotton biomass, yield, and economic benefits while using drip irrigation under mulch (plastic film). We conducted a field experiment for eight consecutive years (2012–2019) in Shawan County of Xinjiang, China. Our experimental results indicated that open ditch and subsurface pipe drainages each reduced total soil salinity, improved saline–sodic soils, and controlled groundwater level, which caused a significant increase in the cotton biomass and yield. The open ditch drainage treatment (ODDA) represented a better desalination effect than the subsurface pipe drainage treatment (SPDA) at 73% and 81%, respectively. The electrical conductivity and pH of ODDA and SPDA water samples decreased as the soil salinities decreased over time. We used the farmland conditions from 2012 as the baseline for our experiment and evaluated how these baseline conditions changed over time in response to these treatments. Compared to this baseline, the cotton yield of ODDA and SPDA treated farmland increased by 18.30 times and 19.96 times in 2019, respectively. The investment payback periods for ODDA and SPDA treatments were 7.59 and 6.34 years, respectively, and their returns on investment were 12% and 30%, respectively. The midterm economic benefits of subsurface pipe drainage were more prominent than those of open ditch drainage. These results provide a reference for improving, developing, and utilizing soil saline–sodic land, and the sustainable development of agriculture in arid areas.

Soil salinization is a global issue that results in soil degradation and affects the sustainable development of irrigated agriculture. A 2-year study was conducted in 2018 and 2019 to identify the effect of subsurface drainage spacing on soil moisture, salt, cotton growth, and yield under the Tarim Basin oasis in China. The tests involved three subsurface drainage treatments, with a pipe spacing of 10 m (W10), 20 m (W20), and 30 m (W30), respectively, and a drainage-absent treatment (CK). Compared with CK, subsurface drainage reduced soil salinity, resulted in better uniform water distribution and reduced inorganic salt concentration in shallow soil solution. In addition to improving soil moisture and salinity conditions, subsurface drainage increased seedling emergence rate (28%), root vigor (23%), and chlorophyll content (44%) of cotton, which in turn led to increases in cotton plant height (18%), leaf area (33%), dry matter weight (32%), and reproductive organ weight (39%), thereby resulting in high cotton yield (45%). A path analysis revealed that under subsurface drainage, the seedling emergence rate of cotton had the greatest impact on cotton yield, and subsurface drainage contributed the most to the increase in cotton yield. It increased the seedling emergence rate by reducing soil salinity. Moreover, cotton yield and next-year soil arability increased with decreasing drainage pipe spacing, suggesting that it is advantageous to adopt a drainage pipe layout with small pipe spacing when economic costs are not a concern.

The dual role of nutrient uptake by plant roots and leaves is one of the main advantages of sprinkler fertigation, while an improper solution concentration suppresses plant physiology and even causes foliar burns. To explore the suitable solution concentrations of nitrogenous fertilizer, phosphate fertilizer and potassium fertilizer, field experiments were conducted at two sites in the North China Plain during the 2019 and 2021 growing seasons of summer maize. The foliar relative chlorophyll content (SPAD), foliar light energy conversion capacity (Fv/F0) and maximum light energy conversion efficiency (Fv/Fm) prior to and after fertilizer solution spraying were measured and compared. In the experiments, six urea concentrations (0.10 − 3.20%), eight monoammonium phosphate concentrations (0.03 − 4.80%) and seven potassium sulfate concentrations (0.10 − 4.80%) were tested during the jointing stage (V6), flare opening stage (V12), heading stage (VT) and filling stage (R2) of summer maize. The results showed that after spraying fertilizer solution, the spatiotemporal variability in Fv/F0 reached moderate from the weak spatiotemporal variability observed prior to spraying. The SPAD values reached moderate from the weak spatiotemporal variability only after spraying nitrogen fertilizer from V6 to VT and after spraying potassium fertilizer from V12 to R2. All the changes in the index variability suggested a great influence of foliar nutrient absorption on plant physiology. Averaged over 5 days following nutrient spraying during the whole season, the average increments synthesized by SPAD, Fv/F0 and Fv/Fm were 1.60, 1.33, and 1.21 times, and the average reductions were 0.62, 0.78 and 0.62 times, respectively. Depending on the fertilizer type and spraying opportunity, the influence of the fertilizer solution on plant physiology changed greatly. To maximize the relative chlorophyll content and photosynthetic capacity of foliar plants resulting from fertilizer solution spraying, the recommended urea solutions were 0.10 − 0.80%, 0.40%, 0.25 − 0.40% and 0.25 − 0.40% during the V6, V12, VT and R2 stages, respectively. For monoammonium phosphate, the suggested concentrations were 0.06 − 0.15%, 0.06 − 0.15%, 0.03 − 0.40% and 0.03 − 0.80%, respectively. Spraying potassium sulfate at a concentration of 0.10 − 0.40% during the V12 and VT stages would benefit plant growth.

This second special issue of the Grape Remote sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX) further advances and expands upon the initial research findings of the first GRAPEX special issue on the measurement and remote sensing of vine water use and stress. This is a highly collaborative and interdisciplinary experiment, which involves USDA-ARS scientists, industry, and university researchers. The large scope of this research has allowed the development of new measurement and remote sensing tools and techniques to quantify vine evapotranspiration, moisture status, and stress, with the ultimate goal of improving irrigation management in California vineyards.

Winter vegetables, including lettuce, are a significant consumptive use of water in the Lower Colorado River Basin. Precise irrigation management is needed to increase water use efficiency and reduce the negative impacts of suboptimal irrigation, including nutrient leaching, crop stress, and crop pathogens. However, lettuce has multiple features that make accurate evapotranspiration (ET) modeling difficult, including asynchronicity with meteorological evaporative demand, short growing seasons, and a shallow root zone that increases the risk of using an incorrect ET value. To improve ET modeling and understand applied irrigation effectiveness for lettuce in this region, we used an energy and water balance bio-physical model, Backward-Averaged Iterative Two-Source Surface temperature and energy balance Solution (BAITSSS) on arid farmlands in the lower Colorado River basin. The study was conducted between 2016 and 2020 at twelve eddy covariance (EC) sites in lettuce with a wide range of soil physical properties. BAITSSS was implemented using ground-based weather and irrigation data, and remote sensing-based vegetation indices (Sentinel-2). The model accuracy varied among sites, with a mean cumulative seasonal ET of ~ 3% and mean RMSE of 1.1 mm d −1 when compared to EC. The results showed that accurate timing and amount of applied water (irrigation and precipitation) were critical to capturing ET spikes right after irrigation and tracking the continuous decrease of ET. This study highlighted the dominant factors that influence the ET of lettuce and how BAITSSS can improve ET modeling for irrigation management.

In this paper, an irrigation scheduling model for banana (Musa sp.) was developed to simulate crop growth and water fluxes under typical commercial plantation conditions. Whilst generic models exist for scheduling irrigation for many crops, their suitability for bananas are limited because of the asynchronous nature of crop growth. Individual fields on banana plantations typically contain trees at varying stages in their development cycle, so it is important for scheduling to account for this heterogeneity in simulating crop production. A crop modelling approach was developed using field data from Magdalena, an economically important region of banana production in Colombia. Following model development and calibration, irrigation water demand was estimated and weekly irrigation scheduling advice then transmitted by SMS to individual farmers in the region. The model also takes into account farmer feedback on actual irrigation practices to compare against estimated irrigation demands and to train model performance. Despite good model calibration, analysis of irrigation practices from farmer feedback showed only moderate to poor correlation between actual irrigation applications and the scheduling guidance. This implies a reluctance of farmers to change long-established traditional irrigation management practices, despite awareness of the impacts of systematic over-irrigation on yields and increased nutrient leaching risks. Significant ongoing research efforts will be needed to support improved knowledge and practical water management for key plantation crops.

To investigate the factors (e.g., water, temperature, fertilizer) that limit maize (Zea mays L.) growth and yield production in Northeast China (NEC), 3 years of field experiments involving different water, fertilizer, and film mulching (to represent temperature variation) treatments were conducted in 2017–2019. The results were analyzed together with historical meteorological data for the region from 1951 to 2019. Five water treatments were applied in 2017 and 2018, while three field management practices (plastic film mulching, biodegradable film mulching, and no mulching) and four nitrogen fertilizer treatments (0–200 kg ha⁻¹) were applied in 2019. Among them, temperature proved to be an important limiting factor in crop production in the region because of crop failure caused by low temperatures and frost in autumn. Water and fertilization also influenced crop growth and production to a certain extent. Both plastic film mulching and biodegradable film mulching improved soil temperature and soil water storage (SWS), particularly during the early growth period. Cumulative soil thermal time (TTsoil) to 100 cm depth increased in the mulching compared with the no mulching treatment. Compared with no mulching, the film mulching also advanced the emergence (VE), sixth-leaf (V6), silking (R1), and milk (R3) stages, by 7, 7, 9, and 9 days, respectively. The improved soil temperature and water conditions and the advanced growth stage under film mulching treatments increased the rate of crop growth and biomass accumulation significantly, with which LAI, biomass, and plant height developed more rapidly than in the no mulching treatment. Film mulching also increased the final grain yield by 21.4–27.6% compared with no mulching. Therefore, film mulching, combined with supplemental irrigation and appropriate fertilization, could be an effective strategy to optimize crop management in Northeast China.

Yield and oil quality responses to different degrees of water stress have often reported for olive trees, but few studies have addressed how midday stem water potential (Ψstem), stomatal conductance (gs), net assimilation (An), and oil yield respond to rewatering after experiencing water deficit. The objective of this study was to evaluate the responses of Ψstem, gs, and An in olive leaves to rewatering after irrigation cut-off (ICO) periods during 2011/2012, 2012/2013, and 2013/2014 growing seasons. The drip-irrigated olive trees were located in the Pencahue Valley (Maule Region, Chile) and trained to a superintensive hedgerow system with a spacing of 1.5 m within rows × 5.0 m between rows. The experiment included a treatment irrigated to satisfy their water requirement based on a previous study (Ψstem > − 2.5 MPa, T0) and two ICO treatments in a completely randomized design. For the ICO treatments, irrigation was cut-off from fruit set until reaching Ψstem thresholds between − 3.0 and − 3.5 MPa for T1 and − 5.0 and − 5.5 MPa for T2. Once these thresholds were reached, the irrigation was restored to that of the T0 treatment level. In the T1 treatment, Ψstem, An, and gs were all fully recovered from moderate water stress, although the time needed for recovery varied between growing seasons. Except 2012/2013 season, the Ψstem values were fully recovered 14 days from rewatering after severe water stress in the T2 treatment. An and gs values were, however, 19–36% and 33–41%, respectively, less than those observed in T0 treatment after even 14 days of rewatering. Finally, the total oil yield per plant was significantly reduced in most study seasons after severe water stress (T2). These results suggest that the evolution of plant water status must be carefully monitored when water deficits are imposed in superintensive olive orchards to avoid unwanted delays in the recovery of photosynthesis and potential reductions in oil yields.

Canopy temperature is generally accepted as an indirect but rapid, accurate, and large-scale indicator of crop water status and is, therefore, proposed to monitor irrigation needs. Crop Water Stress Index (CWSI) is the most widely used among the existing thermal-based indicators, and its links with water stress have been demonstrated. When calculating CWSI using the empirical approach, the differential between canopy and air temperature is normalized by two thresholds, also known as baselines. The Non-water stress baseline (NWSB) in the empirical approach is calculated as the relationship between T c – T a (°C) and the vapor pressured deficit (VPD, kPa) for well-irrigated crops. The baselines display different slopes depending on the species, which have a significant impact on the computed CWSI. This study analyzed the resulting errors on CWSI due to the measurement errors of critical inputs needed for its calculation. Six crop species were selected according to their NWSB with slopes that range from − 0.5 to − 3 °C·kPa ⁻¹ and used for this analysis, assuming measurement errors ranging 0.2–1 °C for T a , 0.25–2 °C for T c , and 5–10% for relative humidity (RH). It was concluded that the effects observed on CWSI are heavily dependent on the slope of the NWSB and therefore vary across species. The calculation was very sensitive to the bias in air and canopy temperature. These errors were maximal as the slope of the NWSB was less steep. When the VPD ranged from 2 to 6.6 kPa, an error of 1 °C in measuring the air temperature affected CWSI between 28 and 83% in orange, which is the species displaying the minimum slope (− 0.5 °C kPa ⁻¹ ). On the contrary, crops with steeper baseline slopes such as squash (− 3 °C kPa ⁻¹ ) showed errors ranging between 2 and 8% for the same VPD interval. This differences among the different crops species considered in this study may be related to the contrasting coupling of the species to the atmosphere, that determines the influence of vapor pressure on the transpiration rate. This study highlights the importance of reliable climatic data and the need for accurate calibrated thermal sensors to calculate CWSI accurately.

Assessment of water consumption is a crucial task for irrigation management in grapevines, especially in areas with limited water resources, which is the case of California Central Valley. This study evaluated the utility of the Simple Algorithm for Evapotranspiration Retrievement (SAFER) model to estimate daily and seasonal actual evapotranspiration (ETa) using Sentinel 2 images at 10-m spatial resolution and 5-day revisit time in 3 vineyards located at two sites in California. A unique characteristic of this model is the estimation of “synthetic” temperature maps, which are used as part of the estimation of ET and energy balance. The SAFER energy balance results were validated with six eddy covariance (EC) flux towers as part of the Grape Remote-sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX). The estimated surface temperature derived from upwelling longwave radiation measurements was closely correlated with the observed sensor surface temperature with R2 higher than 0.86 for the analyzed EC towers. After performing an internal calibration, SAFER root mean square error (RMSE) values on daily ETa were between 0.64 and 0.75 mm day−1. Additionally, the seasonal ETa was estimated and compared with the EC observations showing an average R2 ranging from 0.64 to 0.52 mm/season. Spatial patterns of ETa showed variability between sites and producer management activities. The results found indicate both limitations and potential utility of SAFER for irrigation management in vineyards using daily or seasonal ETa under different irrigation treatments.

The high demand for walnuts in recent years may be related to trends towards the adoption of a healthy and balanced diet. Walnut production is seeking higher yields, early entry into production and kernel quality, with technologies that combine new cultivars, mechanical harvesting, more intensive plant density, and modern irrigation systems. The walnut crop has expanded to non-traditional growing areas, some of which have semiarid climates characterized by low water availability for irrigation. This mini-review focuses on the possible effects of water deficit on plant physiology, kernel yield and quality, based on a comprehensive and comparative analysis of existing information on other dry fruit crops. Some studies estimate the maximum water demand of the walnut at about 1050–1200 mm ha−1 yr−1 with an average seasonal crop coefficient of 0.9, varying according to the phenological stage and agroclimatic characteristics Indicators of water status such as water potential, stomatal conductance, and leaf temperature are evaluated. Sustained and regulated deficit irrigation in walnuts allows a considerable reduction in vegetative growth, with little effect on production while maintaining midday stem water potential above – 0.8 MPa. There are reports of disadvantages to kernel and oil quality mediated by environmental conditions where the water deficit influence requires further study.

Characterization of model errors is important when applying satellite-driven evapotranspiration (ET) models to water resource management problems. This study examines how uncertainty in meteorological forcing data and land surface modeling propagate through to errors in final ET data calculated using the Satellite Irrigation Management Support (SIMS) model, a computationally efficient ET model driven with satellite surface reflectance values. The model is applied to three instrumented winegrape vineyards over the 2017-2020 time period and the spatial and temporal variation in errors are analyzed. We illustrate how meteorological data inputs can introduce biases that vary in space and at seasonal timescales, but that can persist from year to year. We also observe that errors in SIMS estimates of land surface conductance can have a particularly strong dependence on time of year. Overall, meteorological inputs introduced RMSE of 0.33-0.65 mm/day (7-27%) across sites, while SIMS introduced RMSE of 0.55-0.83 mm/day (19-24%). The relative error contribution from meteorological inputs versus SIMS varied across sites; errors from SIMS were larger at one site, errors from meteorological inputs were larger at a second site, and the error contributions were of equal magnitude at the third site. The similar magnitude of error contributions is significant given that many satellite-driven ET models differ in their approaches to estimating land surface conductance, but often rely on similar or identical meteorological forcing data. The finding is particularly notable given that SIMS makes assumptions about the land surface (no soil evaporation or plant water stress) that do not always hold in practice. The results of this study show that improving SIMS by eliminating these assumptions would result in meteorological inputs dominating the error budget of the model on the whole. This finding underscores the need for further work on characterizing spatial uncertainty in the meteorological forcing of ET. Supplementary information: The online version contains supplementary material available at 10.1007/s00271-022-00808-9.

Knowledge regarding uptake of water and nutrients as a function of their status in the soil is critical for smart fertigation management. Of particular interest is the uptake of water and potassium (K), each as a function of root zone salinity. The objective of this study was to quantify the response of tomato water uptake (transpiration) and K uptake to varied levels of K availability combined with salinity. Two independent lysimetric experiments were conducted and used to calibrate and validate models for water and K uptake under varied soil salinity. Tomato water and K uptake were determined by water and nutrient balance using the measured soil water content and K concentration in soil and drainage solution. Tomato water uptake was affected by root zone soil K and salinity. Salinity was the dominant factor driving uptake when irrigation solution had NaCl concentration of over 3 g L–1. Potassium uptake of tomato decreased with decreasing soil K content and increasing soil salinity. The linear relationship between tomato water uptake and K uptake rate was not influenced by soil salinity, indicating that the inhibition of K uptake was probably due to passive uptake of K with the flux of water from soil to roots decreased due to salinity. Tomato water and K uptake were simulated considering the effect of soil solution K concentration under simultaneous K and salinity stresses. Simulated daily average water and K uptake rates agreed well with measured values, with root mean squared error, normalized root mean squared error, and index of agreement of 144 cm³ d–1, 20.13% and 0.99 for average daily water uptake; and 24.43 mg d–1, 29.78% and 0.98 for K average daily uptake rate, respectively. These findings can be used to predict crop water and K requirements under combined salinity and K status conditions, which should contribute to efficient and sustainable fertigation scheduling.

Iran imported around 1.3 million tons of barley in 2017. Accordingly, conducting researches under low organic matter soils and limited water resources is important to enhance barley products and improve economic conditions. Field experiments were performed to evaluate the effect of different levels of irrigation water (0, 50, 75 and 100% of crop water requirement as main plot) and nitrogen fertilizer (0, 70, 140 and 210 kg ha⁻¹; as subplot) on barley (Reyhane 0–3 cv.) growth, agronomic indices and water and nitrogen use efficiency. The results revealed that the barley grain yield dropped by lowering applied water, as the grain yield in 50% irrigation water was around 44% of full irrigation, in both years. Increasing the nitrogen fertilizer to 140 kg ha⁻¹ significantly increased grain yield, while no significant difference was detected between grain yield of 140 kg ha⁻¹ and the highest nitrogen application rate. The maximum water use efficiency was obtained at 75% of full irrigation showing that application of full irrigation did not agronomically increased the grain yield. Nitrogen use efficiency increased by applying more water, while application of nitrogen more than 140 kg ha⁻¹ reduced the nitrogen use efficiency. Furthermore, nitrogen harvest index of 75% indicated that Reyhane 0–3 barley cultivar had the ability to accumulate higher portion of applied N in grain than in straw. Application of 25% deficit irrigation with 140 kg ha⁻¹ nitrogen fertilizer is suggested to obtain the maximum barley production and water use efficiency under semi-arid conditions.

Top-cited authors
• United States Department of Agriculture
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