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Open Access journal
ISSN (Print) 1886-337X - ISSN (Online) 1886-337X
Published by Universitat de Valencia [7 journals]
- Comparison of fluidic and impact sprinklers based on hydraulic performance
Abstract: A comparative study of an outside signal sprinkler (OS), a fluidic sprinkler (FS), and an impact sprinkler (IS) was carried out. The OS, FS, and IS were evaluated individually under indoor experimental conditions. Water distribution evaluations were measured under four operating pressures at a 1.5-m nozzle height (above the ground). Approximately 36 individual trials were performed. The results show that the discharge coefficient of the OS and FS was slightly larger than that of the IS. The water distribution profiles of the OS, FS, and IS were parabola-shaped, ellipse-shaped, and doughnut-shaped, respectively. The wetted radius for the OS was similar to the wetted radius of the FS and was 8.7–12 % less than the IS. An accurate and simple empirical equation for the wetted radius of OS and FS is reported. Additionally, equations of water application rate, with regard to distance from the sprinklers, are given. The average coefficients of determination for the OS, FS, and IS were 91.8, 89.2, and 79.1 %, respectively. Individual spray sprinkler water distributions were mathematically overlapped to calculate the combined uniformity coefficient (CU). Maximal combined CUs of 80.88, 80.92, and 78.12 % were found for the OS, FS, and IS, respectively. Both the OS and FS were found to have greater CU values than the IS, which indicates that the OS and FS provided a better water distribution pattern than the IS at low pressure.
- The influence of irrigation level on olive tree nutritional status
Abstract: While modernization of olive cultivation has recently lead to vast expansion of fully irrigated orchards, characterization of olive tree nutritional status remains based on knowledge gleamed from rain-fed orchards. In the present study, the effect of irrigation level on olive tree nutritional status was investigated in Israel over 4 years on two cultivars and in two locations characterized by differences in soil, tree age, management history, fertilizer application and irrigation water quality. Diagnostic leaves, sampled in July, were evaluated as indicators of nutritional status. Leaf nitrogen concentration was not affected by irrigation level. Leaf phosphorous and potassium concentrations increased with increasing irrigation level. Leaf calcium, manganese and iron tended to decrease with irrigation, while magnesium, sodium and zinc concentrations were not generally affected by irrigation level. Leaf boron and chloride concentrations increased with increasing irrigation when their concentration in irrigation water was relatively high. Leaf nutrient concentration was influenced by cultivar. The results presented in this study emphasize a strong link between irrigation level and the nutritional status of olives for some nutrients and no association for others. These findings should aid in developing distinct fertilization recommendations for fully irrigated olives, different from those developed and used for rain-fed or supplemental-irrigated orchards.
- Hydro-geophysical monitoring of orchard root zone dynamics in semi-arid
Abstract: Monitoring the moisture patterns at the root zone is necessary for agricultural, hydrological, and environmental applications. Conventional monitoring methods are usually invasive, destructive, and only sample at a small spatial scale. Electrical resistivity tomography (ERT) can set an alternative or be complementary to common traditional methods in evaluating the moisture content and its spatiotemporal patterns. In this study, we used the ERT method to monitor the hydro-geophysical dynamics under a drip-irrigated citrus orchard in a semi-arid region. Geophysical surveys were performed monthly for over a year. The obtained data from the electrical measurements were inverted to produce 2D tomograms of the bulk electrical conductivity. Calibrations of the petrophysical relations were conducted using both laboratory and field procedures. The obtained electrical results, and especially their temporal dynamics, cannot always be explained using the common assumption of uniform spatiotemporal distribution of the pore water electrical conductivity. To separate the two main components of the petrophysical relations, namely water content and pore water conductivity, we used a modeling approach. A coupled flow and transport model was calibrated using the electrical conductivity measurements, allowing separation of the contribution of the water content and pore water electrical conductivity to the bulk electrical conductivity. This allowed explaining the temporal dynamics of the measured electrical signal and a better understanding of the water and solute dynamics in the root zone.
- Transpiration of young almond trees in relation to intercepted radiation
Abstract: Increased water scarcity demands more efficient use of water in the agricultural sector which is the primary consumer of water. Precise determination of irrigation requirements based on specific crop parameters is needed for accurate water applications. We conducted a 4-year study on almond evapotranspiration using a large weighing lysimeter. Tree canopies changed from 3 to 48 % ground cover during the course of the study. Sap flow measurements made on the lysimeter tree provided a continuous record of tree transpiration. We propose to use the daily fraction of photosynthetically active radiation intercepted by the canopy (fIRd) as a predictor of almond orchard maximum transpiration. The transpiration coefficient (T/ET o or K T ) was related to the fIRd of the last two years, and the ratio between fIRd and K T stayed more or less constant around a value of 1.2. Such value extrapolated to the size of a mature orchard with 85 % intercepted radiation gives a K T of around 1.0, a number above the standard recommendations, but fully compatible with the maximum K c values of 1.1–1.15 recently reported.
- Modeling soil water dynamics in a drip-irrigated intercropping field under
Abstract: Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm3 cm−3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields.
- Assessment of improved soil hydraulic parameters for soil water content
simulation and irrigation scheduling
Abstract: The efficient irrigation systems utilizing numerical models based on Richard’s flow equation require key input parameters, soil hydraulic parameters (SHPs). The present study proposes a method to determine the SHPs from the soil water contents at field capacity and wilting point, which are determined for irrigation scheduling. It also compares them with the SHPs estimated by various pedotransfer functions (PTFs) to simulate respective soil water retention curves (SWRCs). High efficiencies of 70–80 % were obtained in simulating the SWRCs by the proposed method as compared to PTFs. In order to further assess the applicability of the SHPs as determined, the experiments were conducted under real field conditions for wheat crop in Roorkee, India, and SWRCs were experimentally determined. These different sets of SHPs, along with experimentally determined saturated permeability, were then used as input parameters in root water uptake model and the results of observed and simulated soil water contents were compared under three different irrigation treatments. It was found that the experimentally obtained SHPs and those obtained by the proposed method were able to simulate the soil water contents with efficiencies of 70–80 % at all the depths for all the three irrigation treatments, while the PTFs performed poorly.
- Inhibition of root penetration in subsurface driplines by impregnating the
drippers with copper oxide particles
Abstract: Clogging of subsurface drip irrigation (SDI) systems by root penetration into the emitters results in inappropriate water supply, increased replacement rates of SDI systems and increased costs. We found that impregnation of SDI drippers with copper oxide particles inhibits root penetration very significantly. The inhibition of root penetration varied from 24 to 76 % of the control (60–80 % intrusion) depending on the copper oxide concentration of the drippers. The root penetration inhibition was demonstrated at two water flow rates, of 1 and 3.5 l/h, and with new and used drippers after 1750 irrigation hours. Inhibition of root penetration occurred also if sewage water was used. The inhibition of root penetration into drippers was demonstrated with lettuce and tomato plants and reached similar efficacy as compared to the widely used herbicide Stomp® root penetration inhibition treatment. The amount of copper that leached into the water was below detection limit (less than 0.006 ppm). No loss of copper oxide particles was detected in drippers through which 3350 l of water was passed (an amount of water that typically passes in SDI systems during 3–4 years of use), as determined by scanning electronic microscope and X-ray photoelectron spectrum analysis.
- Using sap flow measurements to estimate net assimilation in olive trees
under different irrigation regimes
Abstract: The measurement of bulk net assimilation (A) in fruit tree species is hindered by the need for sophisticated and complex instrumentation. The aim of this study is to present a simple alternative for estimating A from sap flow measurements and meteorological records. The proposed method was tested in a mature hedgerow olive orchard of 22.2 ha. Within the orchard, an irrigation experiment was established in a small plot including three treatments: a full irrigated control (CI), regulated deficit irrigation (DI) and a treatment mimicking customary orchard irrigation management (FI). Determinations of sap flow, water potential (Ψ) and trunk diameter variations (TDV) were conducted in the three treatments for 3 years. Also, measurements of net ecosystem exchange (NEE) were performed with an eddy covariance system in the centre of the orchard for the first season. The validity of the method was supported by the fact that estimates of A were consistent with both the measured values of NEE and published data regarding the same species under similar environmental and management conditions. Also, differences in A between irrigation treatments were generally in agreement with irrigation applied, transpiration (E p ), Ψ and TDV. It is concluded that the proposed sap flow-based method represents a user-friendly approach to estimate A at the canopy level with potential to study the effects of DI on biomass accumulation.
- SISCO: surface irrigation simulation, calibration and optimisation
Abstract: A model is described which applies the full one-dimensional version of the Saint–Venant equations for open channel flow to simulate the process of surface irrigation. The resulting software for surface irrigation simulation, calibration and optimisation, abbreviated to SISCO, was developed for use in a standard PC environment. Unlike some other models currently in use, SISCO can accommodate temporal variations in inflow rates and spatial variability in soil infiltration, surface roughness, slope and furrow geometry. The main focus of the paper is in regard to the calibration functionality, whereby it is capable of estimating the soil infiltration characteristic and Manning roughness from various combinations of practically obtainable field measurements.
- Efficiency improvement in linear-move sprinkler systems through moderate
Abstract: Given the importance of achieving substantial water and operation savings, automated irrigation management has evolved toward integration of soil moisture measurements with simulation models. The main objective of this study was to develop a set of procedures to maximize irrigation efficiencies in linear-move irrigation systems. A system of field truth data collection and spatially distributed, physically based hydrological modeling was developed to evaluate the efficiencies of linear-move systems considering various naturally occurring boundary conditions and management options. Interactions among the irrigation flow depth, the evaporation conditions, the net infiltration depth and soil moisture uniformity, the irrigation turn duration and runoff–runon production were considered. Environments were of the semiarid Patagonian Monte at varying field slope and antecedent soil moisture. Plot experiments on infiltration and overland flow were used to calibrate a modified version of the CREST hydrological model adapted to the simulation of linear-move irrigation. Modeling results show that irrigation efficiencies can be improved by allowing runoff–runon to occur to an extent compatible with adequate soil moisture uniformity at the end of the irrigation turns. High efficiencies in both attaining effective infiltration depths and minimizing irrigation turn durations may be reached by adjusting the irrigation flow depth through the advance velocity of the irrigation system and/or inter-nozzle distances with due consideration to the antecedent soil moisture condition and the field slope.
- ‘Star Ruby’ grapefruit and ‘Clemenules’ mandarin
trees show different physiological and agronomic responses to irrigation
with saline water
Abstract: The aim of this experiment was to evaluate the effects of saline water irrigation in two citrus species, ‘Clemenules’ mandarin (CLM) and ‘Star Ruby’ grapefruit (SR), both grafted on ‘Cleopatra’ mandarin (a rootstock considered as a Cl− excluder, but a Na+ non-excluder). The experiment was carried out over 3 years (2008–2010) in the IMIDA experimental orchard located at Torre Pacheco (Murcia), using 15-year-old trees irrigated with water of two salinity levels: 0 and 40 mM NaCl. Our data indicate different physiological and agronomic responses of the two citrus species (CLM and SR). The higher salt tolerance observed in CLM was due to the lower accumulation of Cl− in leaves and the greater reduction in vegetative growth with no effect on the quantity or quality of yield. Further, the quality of yield was improved due to the increase in total soluble solids and acidity, since the quality of the juice of CLM fruits is negatively affected in semi-arid regions by lower acidity levels. However, in SR, a high leaf Cl− concentration reduced both vegetative growth and yield and affected fruit quality negatively by increasing the titratable acidity. The increase in the acidity in SR fruits due to salinity translated into a delay of the ripening process, since more time was required to reach optimal levels for the fresh market. Thus, based on these results, we recommend the use of salt-tolerant species such as ‘Clemenules’ mandarin grafted on ‘Cleopatra’ mandarin for semi-arid regions, where the only irrigation water available is saline.
- Effect of drip irrigation frequency on emitter clogging using reclaimed
Abstract: Drip irrigation frequency has important impacts on crop growth, soil moisture, nutrient, salinity and substances’ accumulation in the irrigation system as well as drip irrigation emitter clogging. However, previous studies on reasonable drip irrigation frequency merely focused on crop yield and quality, soil water and salinity transporting, neglecting its impact on the high-efficiency operation of the drip irrigation system. Studies on reasonable reclaimed water drip irrigation frequency were more insufficient. Therefore, the drip irrigation emitter clogging experiment using reclaimed water was accomplished in the wastewater treatment plant, and then, the effects of different irrigation frequencies, including once/2 days (IF1/2), once/4 days (IF1/4), once/8 days (IF1/8) and once/16 days (IF1/16), on dynamic emitters’ outflows and biofilms’ growth were studied. The results showed that emitter clogging degrees increased with shorter drip irrigation interval, mainly because that discharge ratio variation (Dra) and Christiansen uniformity coefficient (CU) both decreased. After the system accumulatively run 540 h, the smallest Dra and CU were observed in high-frequency drip irrigation treatment (IF1/2) as 30.98 and 31.97 %, respectively, along with the highest proportion of more serious clogged emitters, due to the effects of drip irrigation frequencies on the comprehensive biofilm growth and detachment inside emitters. The dry weights (DWs), extracellular polymeric substances (EPS) and phospholipid fatty acids (PLFAs) of biofilms all increased with shorter irrigation interval, and showed logarithmic relationships (R 2 > 0.92). The max DW, EPS and PLFAs of biofilms in IF1/2 reached 0.124 g, 1459.80 and 96.07 μg, respectively, after 540 h. Combined these with previous studying results, irrigated between once/8 days and once/4 days was believed to be appropriate for planting maize in North China Plain using reclaimed water drip irrigation.
- Managing lateral infiltration on wide beds in clay and sandy clay loam
using Hydrus 2D
Abstract: The water productivity of wide beds is largely constrained by poor lateral infiltration. Therefore, field trials were conducted to quantify soil moisture distribution on two soils using three renovation methods [no tillage (NT), shallow cultivation (SC) and blade ploughing (BP)] and four furrow water heads. The aim was to explore strategies for improving lateral infiltration using Hydrus 2D simulation techniques. The results showed increased lateral infiltration and soil water storage with BP, increased vertical infiltration and deep drainage with SC and reduced infiltration with NT treatments. Interestingly, the maximum wetting time of a 2 m wide bed on the clay was ~20 h with NT at a 4-cm furrow water head. This seems achievable under the Australian field conditions. However, the minimum wetting time of a 1.3 m wide bed on the sandy clay loam was 15 h with BP at full furrow water head, which is difficult to manage under short Pakistani furrows with quicker irrigation times. The evaluations and graphical presentations developed can enhance decision support for the optimised irrigation management and bed width design.
- Effects of lateral flushing on emitter clogging and biofilm components in
drip irrigation systems with reclaimed water
Abstract: Emitter clogging has become one of the main restrictions in the development of drip irrigation with reclaimed water. Numerous studies have found that emitter clogging is closely related to the formation and growth of biofilms attached within the emitter wall, raising the question of how to effectively control the formation of biofilms, which is the key to solving emitter clogging. Lateral flushing could promote the rapid shedding of biofilms and wash the irrigation system by increasing the hydraulic shear force within the laterals; this would reduce the frequent shedding of biofilms from the lateral walls into the emitter during the irrigation operation and the clogging of the emitter. Therefore, we conducted an in situ drip irrigation experiment with reclaimed water in a sewage treatment plant under three conditions of lateral flushing frequency (triweekly, biweekly, and weekly), and the dynamic changes in emitter clogging and biofilm components were studied. We found that lateral flushing can effectively slow down emitter clogging in a reclaimed water drip irrigation system. The values for the discharge ratio variation and coefficient of uniformity were the highest, and those for solid particles and phospholipid fatty acids were the lowest for the biweekly lateral flushing frequency. However, lateral flushing failed to completely solve the emitter clogging problem, and some additional measures must be combined with this process to control emitter clogging problems.
- Variable-rate irrigation management using an expert system in the eastern
Abstract: Variable-rate irrigation (VRI) systems have the potential to conserve water by spatially allocating limited water resources. However, when compared to traditional irrigation systems, VRI systems require a higher level of management. In this 3-year study, we evaluated spatial irrigation management of a peanut crop grown under a VRI system using an expert system (Irrigator Pro). The irrigation management treatments evaluated were: (1) using Irrigator Pro (IP) to manage irrigation uniformly in plots with varying soils; (2) using Irrigator Pro to manage irrigation in plots based on the individual soils (IPS); (3) a treatment based on maintaining soil water potential (SWP) above −30 kPa (approximately 50 % depletion of available water) in the surface 30 cm of each soil within a plot; and (4) a non-irrigated treatment. Over the 3-year study, all irrigated treatments had significantly higher yields (4,230, 4,130, and 4,394 kg ha−1 for the IP, IPS, and SWP treatments, respectively) than the non-irrigated treatment (3,285 kg ha−1), yet the yields of the three irrigation treatments were not significantly different. Averaged over the 3-year experiment, the three treatments did not differ significantly in water usage. In the 2007 and 2009 growing seasons with below normal rainfall, the IP and IPS treatments required significantly greater total water than the SWP treatment. Overall, water use efficiency was significantly higher for the non-irrigated and SWP treatments (9.4 and 8.9 kg ha−1 per mm, respectively). The lower water use efficiency for the IP and IPS irrigation treatments (7.8 kg ha−1 per mm) was attributed to greater water applications mainly due to earlier growing season initiation of irrigation applications. However, the IP and IPS treatments maintained soil water potentials at the 30- and 60-cm depths at higher levels throughout most of the season. The two Irrigator Pro expert system treatments functioned as well as the SWP-based treatment. The Irrigator Pro expert system can be effectively used for site-specific management where management zone soils do not greatly differ. Further refinement of the expert system may be needed to improve its application in spatial irrigation applications.
- Quantifying variability in field-scale evapotranspiration measurements in
an irrigated agricultural region under advection
Abstract: This study compares evapotranspiration (ET) measurements from eddy covariance (EC), lysimetry (LY), and water balance using a network of neutron probe (NP) sensors and investigates the role of within-field variability in the vegetation density in explaining the differences among the various techniques. Measurements were collected over irrigated cotton fields during a period of rapid crop growth under advective conditions. Using NP-based ET estimates as reference, differences in cumulative ET measurements from the EC systems and NP ranged between 2 and 14 %, while differences between LY and NP ranged from 22 to 25 %. The discrepancy in the ET between the three methods was largely attributed to variations in vegetation cover within the source areas of the sensors, which was reliably assessed using high-resolution remote sensing imagery. This analysis indicates that the source area contributing to the measurements must be considered, even in instances where one might consider field conditions uniform. Consequently, differences in measured ET require accounting for variability of vegetation cover conditions in measurement source areas, particularly when used for model validation. This point concerning model validation is exemplified by the difference in performance of a thermal-based energy balance model in estimating ET evaluated using LY versus EC measurements.
- Rectangular sharp-crested weir calibration for low head and clinging flow
Abstract: The classical head–discharge relation for rectangular sharp-crested weirs is applicable only to free flow conditions, not valid at low head when flow becomes clinging. Based on experimental data for eight sharp-crested rectangular weirs of different sizes, a new method for calculating discharge at the low head bistable and clinging flow regime was proposed in this study. In the bistable zone, the head–discharge relationship can be covered partly by the classical weir–discharge equations of free flow. The discharge coefficient is quite similar to Rehbock’s equation for free flow with a surface tension term. In the clinging flow regime, the head had to be transformed into an equivalent head obtained by regression. All the regression parameters were about the same for the weirs of different sizes. In the clinging zone, discharge was also directly proportional to weir width, while unit width discharge was directly proportional to the square of head, independent of weir height. The errors of model-predicted discharge were less than 10 % for more than 90 % of the data points. Therefore, the proposed method for discharge of clinging flow is applicable to rectangular sharp-crested weirs at very low head, while the classical formulas often fail under these flow conditions.
- Crop coefficient approaches based on fixed estimates of leaf resistance
are not appropriate for estimating water use of citrus
Abstract: The estimation of crop water use is critical for accurate irrigation scheduling and water licenses. However, the direct measurement of crop water use is too expensive and time-consuming to be performed under all possible conditions, which necessitates the use of water use models. The FAO-56 procedure is a simple, convenient and reproducible method, but as canopy cover and height vary greatly among different orchards, crop coefficients may not be readily transferrable from one orchard to another. Allen and Pereira (Irrig Sci 28:17–34, 2009) therefore incorporated a procedure into the FAO-56 approach which estimates crop coefficients based on a physical description of the vegetation and an adjustment for relative crop stomatal control over transpiration. Transpiration crop coefficients derived using this procedure and fixed values for citrus did not provide good estimates of water use in three citrus orchards. However, when mean monthly leaf resistance was taken into account, good agreement was found with measured values. A relationship between monthly reference evapotranspiration and mean leaf resistance provided a means of estimating mean leaf resistance which estimated transpiration crop coefficients with a reasonable degree of accuracy. The use of a dynamic estimate of mean leaf resistance therefore provided reasonable estimates of transpiration in citrus.
- Accuracy and uniformity of a gravity-feed method of irrigation
Abstract: This paper describes a method of irrigation called measured irrigation (MI). MI is a gravity-feed irrigation system that directly controls the volume of water emitted from each emitter nozzle in each sector during the irrigation event without the need to control the flow rate or the duration of the irrigation event. Three implementations of MI are described: unpowered single-sector MI, solar-powered single-sector MI and solar-powered multi-sector MI. For solar-powered MI, the irrigation frequency is proportional to the evaporation rate minus the precipitation rate. MI does not require access to electricity grid power or to an urban water supply. Trials compare the accuracy and uniformity of MI with pressure-compensating drip irrigation products.
- Operation of an irrigation canal by means of the passive canal control
Abstract: Modern irrigation techniques involve large spatial and temporal demand variations in distribution networks. This makes the flow unsteady and generates perturbations that travel upstream along the network. Perturbations can also be generated by variable water inflows. This is the case when water is pumped into the network under variable energy rates, generating perturbations that travel downstream on the network. The passive canal control is a design criteria and a flow distribution method that make most of the storage capacity needed in any irrigation project, in order to mitigate the perturbations coming from both directions. In this paper, the passive canal control is applied to the design and operation of the Xerta-Sénia Canal Irrigation Project considering an unsteady free-surface flow model. The key aspect of the project is the location of irrigation reservoirs in-line with the canals at the same level, allowing water flow from canals to reservoir and vice versa. Three performance scenarios are evaluated, and the results of a simulation model are presented.