Irrigation Events Research Articles

Water and Fertilizer Use Efficiency in Subirrigated Containerized Tomato

Greenhouse cultivation is highly efficient in the use of water and fertilizers. However, due to intensive production, the greenhouse industry applies ample amounts of water and fertilizers. An alternative to minimize water and nutrient loss is zero-leaching systems, such as closed-loop subirrigation. The objective of the present study was to compare the water and fertilizer use efficiency in containerized tomato plants grown in a subirrigation system and a drip irrigation system. Subirrigated plants exhibited lower biomass than drip-irrigated plants. However, the amount of nutrient solution required to restore evapotranspirated water was lower in subirrigation. The yield was marginally decreased in subirrigated plants compared to drip-irrigated plants. The amount of nutrient solution required to produce 1 kg of fresh tomatoes was 22 L in subirrigation, whereas in drip irrigation, plants demanded 41 L. The total nitrogen applied through the nutrient solution was 75% lower in subirrigation than in drip irrigation, while the phosphorus, potassium, calcium and magnesium applied was 66%, 59%, 70% and 74% lower, respectively. We concluded that the subirrigation system proved to be more water- and nutrient-efficient than the drip irrigation system due to the zero leaching of the nutrient solution, the lower number of irrigation events required and the lower nutrient demand of plants.

Near Real-Time Irrigation Detection at Plot Scale Using Sentinel-1 Data

In the context of monitoring and assessment of water consumption in the agricultural sector, the objective of this study is to build an operational approach capable of detecting irrigation events at plot scale in a near real-time scenario using Sentinel-1 (S1) data. The proposed approach is a decision tree-based method relying on the change detection in the S1 backscattering coefficients at plot scale. First, the behavior of the S1 backscattering coefficients following irrigation events has been analyzed at plot scale over three study sites located in Montpellier (southeast France), Tarbes (southwest France), and Catalonia (northeast Spain). To eliminate the uncertainty between rainfall and irrigation, the S1 synthetic aperture radar (SAR) signal and the soil moisture estimations at grid scale (10 km × 10 km) have been used. Then, a tree-like approach has been constructed to detect irrigation events at each S1 date considering additional filters to reduce ambiguities due to vegetation development linked to the growth cycle of different crops types as well as the soil surface roughness. To enhance the detection of irrigation events, a filter using the normalized differential vegetation index (NDVI) obtained from Sentinel-2 optical images has been proposed. Over the three study sites, the proposed method was applied on all possible S1 acquisitions in ascending and descending modes. The results show that 84.8% of the irrigation events occurring over agricultural plots in Montpellier have been correctly detected using the proposed method. Over the Catalonian site, the use of the ascending and descending SAR acquisition modes shows that 90.2% of the non-irrigated plots encountered no detected irrigation events whereas 72.4% of the irrigated plots had one and more detected irrigation events. Results over Catalonia also show that the proposed method allows the discrimination between irrigated and non-irrigated plots with an overall accuracy of 85.9%. In Tarbes, the analysis shows that irrigation events could still be detected even in the presence of abundant rainfall events during the summer season where two and more irrigation events have been detected for 90% of the irrigated plots. The novelty of the proposed method resides in building an effective unsupervised tool for near real-time detection of irrigation events at plot scale independent of the studied geographical context.

Influence of Poultry Litter Amendment Type and Irrigation Events on Survival and Persistence of Salmonella Newport

Salmonella enterica subsp. enterica serovar Newport is a bacterial foodborne pathogen isolated from several environmental reservoirs on the Delmarva Peninsula and has been associated with several produce-related outbreaks. However, little is known about specific interactions between Salmonella Newport and soil amendments used as fertilizers. The purpose of this study was to determine Salmonella Newport persistence and resuscitation in raw poultry litter (PLR), a common biological soil amendment, and in soils containing poultry litter-based (heat-treated poultry pellets [HTPP]) or chemical fertilizer (urea [U]) amendments to provide equivalent levels of nitrogen to the soil. Inoculated samples were stored in a growth chamber and irrigated regularly over 4 weeks. Soil samples were collected every week for 4 weeks to determine moisture content and surviving Salmonella Newport populations (log CFU per gram dry weight). Data were analyzed by using a one-way analysis of variance and Student's t test. The PLR supported significantly higher (5.07 log CFU/g dry weight [gdw]) populations of Salmonella Newport than HTPP only (1.70 log CFU/gdw). However, PLR-amended (PRLA) soil (2.5 log CFU/gdw) samples had significantly (P < 0.05) lower Salmonella Newport populations compared with HTPP-amended (4.5 log CFU/gdw) and U-amended (4.0 log CFU/gdw) soil samples. The effect of irrigation on Salmonella Newport population levels in PRLA soils was significant, and in a comparative study, the overall increase in the pathogen levels in U-amended soil (mean = 1.12 log CFU/gdw) was significantly greater than that in PLRA soil (mean = 0.54 log CFU/gdw), whereas that in HTPP-amended soil (0.80 log CFU/gdw) was not significantly different from PLRA soil.

Effect of intercropping madumbe (Colocasia esculenta) and rice (Oryza sativa L.) on yield and land productivity under different irrigation water management techniques with effluent water

The need for the optimal use of land, without a yield penalty, in urban and peri-urban (UP) settlements is vital. This study investigated the effect of intercropping madumbe and rice with respect to yield and land productivity when irrigated with anaerobic baffled reactor (ABR) effluent under different irrigation water management techniques. It was hypothesized that intercropping under different irrigation water management techniques has no effect on the yield and land productivity. Field trials were conducted in the 2017 and 2018 cropping seasons with ABR effluent (without fertilizer) at the Newlands Mashu Experimental Site, Newlands East, Durban, South Africa. A randomized complete block design with 3 replications; cropping treatments of sole madumbe, sole rice and madumbe + rice (intercrop) and irrigation treatments of alternate wetting and drying (AWD), continuous flood irrigation (CFI) and wetting without flooding (WWF) was used. Growth and yield parameters at harvest were determined. Thereafter, land equivalent ratio (LER) was calculated to evaluate the productivity of the intercrop. The effect of intercropping was significant (P &lt; 0.05) on the total number of irrigation events and total water use. There was a significant reduction (P &lt; 0.05) in plant heights of both madumbe and rice at intercrop. However, the effect on plant height for treatment CFI was positive but not significant (P &gt; 0.05) for both seasons. A significant (P &lt; 0.05) reduction also occurred in the number of madumbe leaves/plant, and panicles/plant and tillers/plant for rice. Intercropping significantly reduced (P &lt; 0.05) madumbe corm and rice grain yield over the two seasons relative to sole cropping. LER showed that intercropping madumbe with rice was not more productive (LER &lt; 1) than sole cropping of madumbe. It was concluded that over the two-season period, intercropping madumbe and rice do not yield appreciably under any of the three irrigation management techniques applied and the study hypothesis is thus rejected.

Effect of intercropping madumbe (Colocasia esculenta) and rice (Oryza sativa L.) on yield and land productivity under different irrigation water management techniques with effluent water

The need for the optimal use of land, without a yield penalty, in urban and peri-urban (UP) settlements is vital. This study investigated the effect of intercropping madumbe and rice with respect to yield and land productivity when irrigated with anaerobic baffled reactor (ABR) effluent under different irrigation water management techniques. It was hypothesized that intercropping under different irrigation water management techniques has no effect on the yield and land productivity. Field trials were conducted in the 2017 and 2018 cropping seasons with ABR effluent (without fertilizer) at the Newlands Mashu Experimental Site, Newlands East, Durban, South Africa. A randomized complete block design with 3 replications; cropping treatments of sole madumbe, sole rice and madumbe + rice (intercrop) and irrigation treatments of alternate wetting and drying (AWD), continuous flood irrigation (CFI) and wetting without flooding (WWF) was used. Growth and yield parameters at harvest were determined. Thereafter, land equivalent ratio (LER) was calculated to evaluate the productivity of the intercrop. The effect of intercropping was significant (P &lt; 0.05) on the total number of irrigation events and total water use. There was a significant reduction (P &lt; 0.05) in plant heights of both madumbe and rice at intercrop. However, the effect on plant height for treatment CFI was positive but not significant (P &gt; 0.05) for both seasons. A significant (P &lt; 0.05) reduction also occurred in the number of madumbe leaves/plant, and panicles/plant and tillers/plant for rice. Intercropping significantly reduced (P &lt; 0.05) madumbe corm and rice grain yield over the two seasons relative to sole cropping. LER showed that intercropping madumbe with rice was not more productive (LER &lt; 1) than sole cropping of madumbe. It was concluded that over the two-season period, intercropping madumbe and rice do not yield appreciably under any of the three irrigation management techniques applied and the study hypothesis is thus rejected.

Multitracer irrigation experiments for assessing the relevance of preferential flow for non-sorbing solute transport in agricultural soil

This study addresses the relevance of preferential flow for the transport of a non-sorbing solute in a sandy agricultural field with nitrate-contaminated groundwater. Two multitracer irrigation experiments were conducted 1) in October 2017, and 2) in March 2018 on a 2 m × 2 m plot on an agricultural field in Northern Germany (Cloppenburg region). For irrigation 1, Cl-, H218O, and 15NO3- were used as tracers, for irrigation 2, Br-, 2H2O, and 15NO3- were used as tracers. Between both irrigation events the study plot was subject to natural precipitation. The study plot was instrumented with soil moisture sensors and suction plates. The occurrence of preferential flow was studied based on the following data: (1) tracer breakthrough curves collected by five suction plates; (2) the spatial distribution of resident tracer concentrations in soil at the end of the experiment; and (3) 3D-time lapse electrical resistivity tomography (ERT) during both irrigation events. The spatial distribution of water residence times at the end of the experiment was calculated based on measured tracer concentrations in the soil and the known fingerprints of three sources of water (irrigation 1, rain and irrigation 2) applied to the plot. The relevance of preferential flow for the leaching of a non-sorbing solute was assessed by comparing the observed and Hydrus-1D-modeled cumulative leaching of Cl-.In comparison to the conservative tracers 1–11% of the applied 15NO3- was removed from soil solution most probably due to microbial processes. Continuous preferential flow paths were observed below the plow pan. The same preferential flow paths seem to be used repeatedly by the successive rain/irrigation events. However, the mobile-immobile regions appear to exist only for a short period of time, because fast matrix flow balances the spatial heterogeneity in tracer distribution. The residence time of soil water varied from 1 to 3 months at 40–50 cm depth and was not older than 4 months at 190–200 cm depth. Hydrus-1D transient model calculations predicted 13%-30% less leaching of a conservative tracer during wintertime compared to the experimentally estimated averaged leaching from our study plot. Therefore, our main result is that preferential flow, though responsible for a high spatial heterogeneity in leaching loads within study plot in our non-structured sandy soil, increased only slightly the averaged cumulative solute leaching during wintertime from the plot.

Dynamic Simulation Tool of fertigation in drip irrigation subunits

Agriculture consumes approximately 95 million tonnes of fertilizers and 97,000 tonnes of active ingredients of pesticides and herbicides. Reducing external input systems can result in significant economic, social and environmental impact. Therefore, establishing an optimal fertigation schedule is essential to achieve efficient drip irrigation management and, therefore, achieve an optimal irrigated agriculture management system that ensures productive, environmental and economic viability. The objective of this study was to develop a decision support system (DSS) to facilitate farmers’ decision-making process and optimize the design and management of farm fertigation scheduling. Implemented in MATLAB®, FERTI-DRIP, was tested in a regular irrigation subunit and in an irregular irrigation subunit of a real water user association. Both irrigation subunits were tested with two irrigation emitter types: pressure-compensating emitters and non-pressure-compensating emitters. Thus, FERTI-DRIP was applied to four scenarios to analyse the effect of the size and shape of the irrigation subunit on the fertigation process. The effect of the pressure head in the irrigation subunit and the effect of the fertilizer dynamics during the fertigation event were also analysed. FERTI-DRIP allows users to compute fertilizer quality parameters to determine how to implement fertigation. FERTI-DRIP also allows users to accurately select pre-fertigation and post-fertigation processes to optimize hydraulic stability at the beginning of the fertigation event and ensure that there is no fertilizer remaining in the irrigation system after the fertigation event. FERTI-DRIP can be very helpful for start-time irrigation events, such in the case of sandy soils where pulse drip irrigation should be performed.

Optimizing Overhead Irrigation Droplet Size for Six Mississippi Soils

Optimizing overhead irrigation practices will ensure that water loss is minimized, and each unit of water is used most effectively by the crop. In order to optimize overhead irrigation setup, a study was conducted over two years in Mississippi to quantify the optimal overhead irrigation duration and intensity for six soil types commonly found in row-crop production regions in the state. Each soil type was transferred to containers and measured for total water infiltration and water infiltration over time using a two-nozzle rainfall simulator in a track sprayer. The rainfall simulator was calibrated to apply 2.1 mm of water per minute. The rainfall simulator ran on a 2.4 m track for 90 s, with 3.2 mm total water applied during that time. After the 90 s overhead irrigation event, each container was undisturbed for 150 s and assessed for irrigation penetration through the soil profile. Commercially available irrigation nozzles were measured for droplet size spectrum. Results showed that across soil type, organic matter was the primary factor affecting water infiltration through the profile, followed by soil texture. Irrigation nozzle volumetric median droplet sizes ranged from 327 µm to 904 µm. The results will improve overhead irrigation setup in Mississippi, improving irrigation water use efficiency and reducing losses from soil erosion over the application of water and reduced crop yield.

Sorption and desorption of seven steroidal synthetic progestins in five agricultural soil-water systems.

Manure fertilization and wastewater irrigation can introduce the biologically potent synthetic progestins into agricultural soils, causing endocrine disruption in organisms of nearby surface waters. Therefore, this study investigated the sorption and desorption potential of etonogestrel, medroxyprogesterone, gestodene, norgestrel, cyproterone acetate, levonorgestrel, and dienogest in five agricultural soil-water systems. Sorption data were well-described by the linear sorption model. In most batch systems, cyproterone acetate exhibited the highest affinities for soils, followed by etonogestrel, medroxyprogesterone, levonorgestrel, gestodene, norgestrel, and dienogest. The sorption magnitudes (logKoc or logKd) were significantly correlated with the progestin hydrophobicities (R2=0.72-0.86, p<0.05). The Kd values of the progestins were also significantly correlated with organic carbon content and pore volumes of the soils (R2=0.68-0.98, p<0.05). In addition, 0.5M urea resulted in 3-19% decreases in Kd values of the progestins. Taken together, these data indicated that hydrophobic partitioning interaction, hydrogen bonding interaction, and pore filling were the sorption mechanisms for the progestins in soil-water systems. No significant desorption hysteresis was observed for the progestins, indicating that they can be readily desorbed under rainfall or irrigation events. Based on the sorption and desorption data, we estimated the dynamic transport of the progestins in conventional agricultural management systems, and predicted the concentrations of the progestins as a function of soil-sorbed concentration, water-soil ratio, and dilution factor of receiving waters. This study will improve the understanding of the risks posed by the progestins under field-scale hydrological conditions.

Effect of micro-dams on water flow characteristics in furrow irrigation

Surface irrigation, particularly furrow irrigation, is the most common method of water application into agricultural lands. Despite all its advantages, furrow irrigation has some demerits, such as a potential large volume of runoff losses. In this research, an approach was proposed to reduce runoff losses and to improve water flow characteristics by creating micro-dams, barriers inside the irrigated furrows. To control water flow and increase infiltration into the soil, experimental micro-dams were created at distances of 10 and 20 m, with a height of 5 cm. Field experiments were conducted at the research farm of the College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran in summer of 2018. Two erosive inflow rates (0.6 and 0.9 L/s) were considered. Furrow length and spacing were 100 and 0.75 m, respectively. Results indicated that micro-dams increased the advance time, leading to increased infiltration. Micro-dams also increased the recession time, due to the increase in overland water volume. Moreover, results showed that in treatments with micro-dams, runoff was reduced by up to 45.3% in comparison to the control treatment. The change in furrow cross-sectional area during the irrigation event was also reduced. Micro-dams showed a great potential to reduce irrigation runoff losses, and should be considered as a management practice aiming at water and soil conservation.

Thermal imaging of a hydrophobic soil’s response to surfactant application at the Avon River Catchment Critical Zone Observatory

The hydrology of water repellent soil is poorly understood, in part because measuring hydrophobicity often interferes with subsequent water flow. Since soil surface temperatures provide information on near surface water content, thermography offers the potential to indirectly monitor this hydrology non-invasively. Using a near-infrared thermal camera, 15 plots, each 1 m2, of a hydrophobic sandy topsoil were recorded continuously for three weeks in the field. Treatments included plots with surfactant applied in bands from 16 cm to 100 cm width and a control (no surfactant). Soil sampling and continuous monitoring of soil moisture, soil temperature and weather conditions supplemented surface temperature measurements. Surface temperature and surface soil moisture were shown to be negatively correlated during the day and positively at night. Soil moisture probes indicated that water from three 10 mm irrigation events was largely restricted to depths less than 10 cm throughout the experiment. Dynamics of the semi-variance for treated plots were different to that of the control. Empirical orthogonal functionals (EOF) initially showed the dominant variability in spatial pattern reflected the surfactant application. During the course of the experiment, changes in the EOFs revealed the gradual re-emergence of background soil heterogeneity related to prior seeding rows. The monitoring did not reveal any lateral expansion of wetted areas from the edges of surfactant treated strips. Thermography was able to inform the dynamics of soil moisture related to spatial and temporal variability in hydrophobicity under field conditions. The approach offers the potential to non-invasively image dynamic soil hydraulic properties and to evaluate water repellence amelioration methods.

Determining optimal water and nitrogen management under different initial soil mineral nitrogen levels in northwest China based on a model approach

Determining the best management practices (BMPs) under different initial soil mineral N (ISMN) levels is helpful to improve water and N use efficiencies (WUE, NUE) and protect the environment. In this study, a two-year field experiment of spring maize was conducted from 2014 to 2015 in northwest China. Five treatments were designed, including one local farmer practice (I480-4N280, 280 kg N ha−1 fertilizer and irrigated 480 mm with four irrigation events) and four conservation treatments (I420-4N200, I420-5N200, I420-6N200 and I420-7N200, standing for 200 kg N ha−1 fertilizer and irrigated 420 mm with four to seven irrigation events, respectively). Measured yield, leaf area index, soil water content and soil nitrate concentration were used to evaluate a soil-crop model (WHCNS, soil Water Heat Carbon Nitrogen Simulator), which was then used to simulate the effects of water and N management practices on water consumption, N fates, and crop growth. Then, the integrated index considering the agronomic, economic, and environmental impacts was simulated using 35,100 combinations of irrigation and fertilizer N scenarios, which were designed to develop BMPs under different ISMN levels (ranging from 0 to 625 kg N ha-1 in a 1.8 m-soil profile) and seasons of weather data (from 2001 to 2015). Results showed I420-5N200 was the best with a high yield, WUE and NUE, and low N loss among five treatments. The optimal irrigation amount (ranging from 350−600 mm) was related to precipitation amount. The optimal N rate decreased linearly with the increase of ISMN when ISMN was <384 kg ha−1, and reached a plateau (0 kg N ha−1) when ISMN was >384 kg ha−1. In this study, we developed a simple linear model to determine the best N application rates under different ISMNs. This method is important to help farmers achieve multiple goals of high yield, resource conservation and reduced environmental impacts simultaneously.

Spatio-temporal variability of soil moisture in a cropped agricultural plot within the Ganga Basin, India

Soil moisture dynamics in response to rainfall and irrigation events were examined using data obtained from continuous point measurements carried out under rice and wheat crops for an agricultural plot located within the Ganga Basin, India. Soil moisture data were collected using SM100 and SMEC300 sensors at 18 subplots and at four different depths (0−80 cm) during the period from 5 August 2018 to 31 March 2019. Soil moisture was decomposed into temporal mean and temporal anomalies components, and its variability was characterized considering both absolute soil moisture and temporal anomalies. They exhibited similar patterns at all the depths under rice crop cover. However, it varies with depth under wheat crop cover due to periodic wetting and drying conditions and temporally variable atmospheric demand. Similarly, the spatial variance of absolute soil moisture was decomposed into time-invariant and time-variant components. The results revealed that the time-invariant component contribution was dominant at all the depths (72.49–101.46 %) and the contribution of each component varies with soil wetness and land cover. In addition, temporal stability analysis of soil moisture was carried out. It was observed that the spatial pattern at surface depth cannot be preserved for subsurface depths, and similar subplots were found to be temporally stable at the surface and bottom depths under different crop covers. The results are expected to help improve the understanding of the nature of soil water dynamics in agricultural fields.

Assessment of Water Balance and Traditional Surface Irrigation Practices in the Northern Nile Delta

Water balance analysis helps in managing water supply. Therefore, matching between water supply and demand is very important to overcome water shortage.This study aims at presenting comprehensive analysis to understand the nature of operating system in the traditional surface irrigation systems aiming to establish a comprehensive analysis to sustain the irrigation system, considering the problems of water supply, inequity, water quality deterioration, and poor irrigation and drainage management. Analysis in this study was done in two hubs. Firstly, study the parameters affecting water supply and demand; secondly, assessing water availability, adequacy, equity and distribution of irrigation during 24 hours’ cycle.The study area is located in Kafr El-Dawar irrigation district, El-Beheira governorate in the western part of the Nile Delta.The findings show that the differences in water balance per feddan (feddan is an Egyptian land unit equals 4206 m2) at all tertiary canals (meskas) are small; At the head of the canals, no night irrigation or drainage water reuse events during the irrigation seasons were observed; and the irrigation rotation is irregular. These findings elaborate that the location on the canal and the presence of subsurface drainage are mainly affecting the water balance in the study area.

Irrigation Scheduling Based on Wireless Sensors Output and Soil-Water Characteristic Curve in Two Soils.

Data-driven irrigation planning can optimize crop yield and reduce adverse impacts on surface and ground water quality. We evaluated an irrigation scheduling strategy based on soil matric potentials recorded by wireless Watermark (WM) sensors installed in sandy loam and clay loam soils and soil-water characteristic curve data. Five wireless WM nodes (IRROmesh) were installed at each location, where each node consisted of three WM sensors that were installed at 15, 30, and 60 cm depths in the crop rows. Soil moisture contents, at field capacity and permanent wilting points, were determined from soil-water characteristic curves and were approximately 23% and 11% for a sandy loam, and 35% and 17% for a clay loam, respectively. The field capacity level which occurs shortly after an irrigation event was considered the upper point of soil moisture content, and the lower point was the maximum soil water depletion level at 50% of plant available water capacity in the root zone, depending on crop type, root depth, growth stage and soil type. The lower thresholds of soil moisture content to trigger an irrigation event were 17% and 26% in the sandy loam and clay loam soils, respectively. The corresponding soil water potential readings from the WM sensors to initiate irrigation events were approximately 60 kPa and 105 kPa for sandy loam, and clay loam soils, respectively. Watermark sensors can be successfully used for irrigation scheduling by simply setting two levels of moisture content using soil-water characteristic curve data. Further, the wireless system can help farmers and irrigators monitor real-time moisture content in the soil root zone of their crops and determine irrigation scheduling remotely without time consuming, manual data logging and frequent visits to the field.

Impact of Deficit Irrigation on Shallow Saline Groundwater Contribution and Sunflower Productivity in the Imperial Valley, California

Yield and production functions of sunflower (Helianthus annuus) were evaluated under full and deficit irrigation practices with the presence of shallow saline groundwater in a semi-arid region in the Imperial Valley of southern California, USA. A growing degree day (GDD) model was utilized to estimate the various growth stages and schedule irrigation events throughout the growing season. The crop was germinated and established using overhead irrigation prior to the use of a subsurface drip irrigation (SDI) system for the remainder of the growing season. Four irrigation treatments were implemented: full irrigation (100% full sunflower crop evapotranspiration, ETC), two reduced irrigation scenarios (95% ETC and 80% ETC), and a deficit irrigation scenario (65% ETC). The salinity of the irrigation water (EC) (Colorado River water) was nearly constant at 1.13 dS·m−1 during the growing season. The depth to groundwater and groundwater salinity (ECGW) were continuously monitored in five 3 m deep observation wells. Depth to groundwater fluctuated slightly under the full and reduced irrigation treatments, but drastically increased under deficit irrigation, particularly toward the end of the growing season. Estimates of ECGW ranged from 7.34 to 12.62 dS·m−1. The distribution of soil electrical conductivity (ECS) and soil matric potential were monitored within the active root zone (120 cm) at selected locations in each of the four treatments. By the end of the experiment, soil salinity (ECS) across soil depths ranged from 1.80 to 6.18 dS·m−1. The estimated groundwater contribution to crop evapotranspiration was 9.03 cm or approximately 16.3% of the ETC of the fully irrigated crop. The relative yields were 91.8%, 82.4%, and 83.5% for the reduced (95% and 80% ETC) and deficit (65% ETC) treatments, respectively, while the production function using applied irrigation water (IW) was: yield = 0.0188 × (IW)2 − 15.504 × IW + 4856.8. Yield reduction in response to water stress was attributed to a significant reduction in both seed weight and the number of seed produced resulting in overall average yields of 2048.9, 1879.9, 1688.1, and 1710.3 kg·ha−1 for the full, both reduced, and deficit treatments, respectively. The yield response factor, ky, was 0.63 with R2 = 0.745 and the irrigation water use efficiencies (IWUE) were 3.70, 3.57, 3.81, and 4.75 kg·ha−1·mm−1 for the full, reduced, and deficit treatments, respectively. Our results indicate that sunflowers can sustain the implemented 35% deficit irrigation with root water uptake from shallow groundwater in arid regions with a less than 20% reduction in yield.

DEVELOPMENT AND APPLICATION OF A SEASONAL FURROW IRRIGATION MODEL (SFIM)

AbstractIf furrow irrigation is properly designed and implemented, this method would be one of the best surface irrigation systems. To achieve high irrigation efficiency and uniformity in surface irrigation, the use of simulation models is inevitable. The purpose of this study was to develop a seasonal furrow irrigation model to simulate the whole irrigation season (every irrigation event). The model called ‘SFIM’ was developed using the FORTRAN programming language. SFIM consists of four sub‐models to simulate surface flow, subsurface flow, crop yield, water productivity and irrigation evaluation indices. Three data sets of furrow irrigation for maize crop production in the Alborz Province of Iran (College of Agriculture and Natural Resources and Seed and Plant Improvement Institute farms) were used for evaluation of the proposed model. Average relative error of the model ranged from 11.5 to 17.2%, 7.5 to 11.3% and 6.8 to 9.0% in estimating infiltrated water volume, crop yield and water productivity, respectively. The model could also well simulate temporal soil moisture variations and water stress in the root zone. As a consequence, the SFIM model could successfully simulate all irrigation events during the maize‐growing season. © 2020 John Wiley &amp; Sons, Ltd.

Data-Driven Models for Canopy Temperature-Based Irrigation Scheduling

HighlightsArtificial neural network modeling was used to predict crop water stress index lower reference canopy temperature.Root mean square error of predicted lower reference temperatures was &amp;lt;1.1°C for sugarbeet and Pinot noir wine grape.Energy balance model was used to dynamically predict crop water stress index upper reference canopy temperature.Crop water stress index for sugarbeet was well correlated with irrigation and soil water status.Crop water stress idex was well correlated with midday leaf water potential of wine grape.Abstract. Normalized crop canopy temperature, termed crop water stress index (CWSI), was proposed over 40 years ago as an irrigation management tool but has experienced limited adoption in production agriculture. Development of generalized crop-specific upper and lower reference temperatures is critical for implementation of CWSI-based irrigation scheduling. The objective of this study was to develop and evaluate data-driven models for predicting the reference canopy temperatures needed to compute CWSI for sugarbeet and wine grape. Reference canopy temperatures for sugarbeet and wine grape were predicted using machine learning and regression models developed from measured canopy temperatures of sugarbeet, grown in Idaho and Wyoming, and wine grape, grown in Idaho and Oregon, over five years under full and severe deficit irrigation. Lower reference temperatures (TLL) were estimated using neural network models with Nash-Sutcliffe model efficiencies exceeding 0.88 and root mean square error less than 1.1°C. The relationship between TLL minus ambient air temperature and vapor pressure deficit was represented with a linear model that maximized the regression coefficient rather than minimized the sum of squared error. The linear models were used to estimate upper reference temperatures that were nearly double the values reported in previous studies. A daily CWSI, calculated as the average of 15 min CWSI values between 13:00 and 16:00 MDT for sugarbeet and between 13:00 and 15:00 local time for wine grape, were well correlated with irrigation events and amounts. There was a significant (p &amp;lt; 0.001) linear relationship between the daily CWSI and midday leaf water potential of Malbec and Syrah wine grapes, with an R2 of 0.53. The data-driven models developed in this study to estimate reference temperatures enable automated calculation of the CWSI for effective assessment of crop water stress. However, measurements taken under conditions of wet canopy or low solar radiation should be disregarded as they can result in irrational values of the CWSI. Keywords: Canopy temperature, Crop water stress index, Irrigation scheduling, Leaf water potential, Sugarbeet, Wine grape.

Superabsorbent polymer characteristics, properties, and applications

AbstractSuperabsorbent polymers (SAPs) are materials that can absorb significant amounts of water relative to their mass. The nature and properties of SAPs make them a widely utilized material across many disciplines. A systematic review was conducted to examine the use of SAPs within agriculture and environmental science. The method of application, rate, and the subsequent impact on soil properties were determined. Superabsorbent polymers can be used to improve and prolong soil water holding capacity, decrease drought stress, and increase time between irrigation events. There are results indicating SAPs can reduce compaction. Yield and plant growth characteristics were improved for all but one of the reviewed studies. While SAPs show potential as a tool, their economic feasibility on large‐scale and long‐term projects should be evaluated.

Sub-Surface Drip Irrigation in Associated with H2O2 Improved the Productivity of Maize under Clay-Rich Soil of Adana, Turkey

Maize being sub-tropical crop is sensitive to water deficit during the early growth stages; particularly clay-rich soil, due to the compaction of the soil. It is well-documented that potential sub-surface drip irrigation (SDI) (Full irrigation; SDIFull (100% field capacity (FC)), Deficit irrigation; SDIDeficit (70% FC)) improves water use efficiency, which leads to increased crop productivity; since it has a constraint that SDI excludes soil air around the root-zone during irrigation events, which alter the root function and crop performance. Additionally, in clayrich soils, the root system of plants generally suffers the limitation of oxygen, particularly the temporal hypoxia, and occasionally from root anoxia; while SDI system accomplishes with the aerating stream of irrigation in the rhizosphere could provide oxygen root environment. The oxygen can be introduced into the irrigation stream of SDI through two ways: the venturi principle, or by using solutions of hydrogen peroxide through the air injection system. Therefore, the application of hydrogen peroxide (H₂O₂; HP) can mitigate the adverse effect of soil compactness and also lead to improving the growth, yield and yield attributes of maize in clay-rich soil. Considering the burning issue, a field study was conducted in consecutive two seasons of 2017 and 2018; where hybrid maize was cultivated as a second crop, to evaluate the effect of liquid-injection of H₂O₂ (HP) into the irrigation stream of SDI on the performance of maize in a clay-rich soil field of Adana, Turkey. When soil water content decreased in 50% of available water, irrigation was performed. The amount of water applied to reach the soil water content to the field capacity is SDIFull (100% FC) and 70% FC of this water is SDIDeficit (70% FC). In the irrigation program, hydrogen peroxide (HP) was applied at intervals of 7 days on average according to available water with and without HP: SDIFull (100% FC) + 0 ppm HP with full SDI irrigation; SDIFull (100% FC) + 250 ppm HP with deficit SDI irrigation; SDIDeficit (70% FC) + 0 ppm HP, SDIDeficit (70% FC) + 250 ppm HP and SDIDeficit (70% FC) + 500 ppm HP. Deficit irrigation (SDIDeficit (70% FC)) program was started from tasseling stage and continued up to the physiological maturity stage with sub-soil drip irrigation. H₂O₂ was applied 3 times during the growing season. Two years’ results revealed that the liquid-injection of H₂O₂ into the irrigation stream of SDI improved the growth and yield-related attributes and grain yield of maize. Based on the obtained results, during the extreme climatic condition in the year 2017, SDIFull (100% FC) + 250 ppm HP was more effective than SDIFull (100% FC) + 0 ppm HP on all traits for relative to full irrigation. While, during the favourable climatic condition in the 2018 season, SDIFull (100% FC) + 250 ppm HP was more effective than full irrigation with SDIFull (100% FC) + 0 ppm HP for the grain yield, grains, and SPAD value. Accordingly, the most effective treatment was SDIFull (100% FC) + 250 ppm HP, as it gave the highest growth and yield-related attributes and grain yield of maize followed by SDIDeficit (70% FC) + 250 ppm HP. Therefore, SDIFull with 250 ppm H₂O₂ using as liquid-injection may be recommended to mitigate the adverse effect of soil compactness particularly water-deficit stress in clay-rich soil for the sustainability of maize production.