Papers by Naftali Lazarovitch
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights s u m m a r y Groundwater is often the most or only feasible safe drinking water source in remote, low-resource areas, yet the economics of its development have not been systematically outlined. We applied AWARE (Assessing Water Alternatives in Remote Economies), a recently developed Decision Support System, to investigate the costs and benefits of groundwater access and abstraction for non-networked, rural supplies. Synthetic profiles of community water services (n = 17,962), defined across 13 parameters' values and ranges relevant to remote areas, were applied to the decision framework, and the parameter effects on economic outcomes were investigated. Regressions and analysis of output distributions indicate that the most important factors determining the cost of water improvements include the technological approach, the water service target, hydrological parameters, and population density. New source construction is less cost-effective than the use or improvement of existing wells, but necessary for expanding access to isolated households. We also explored three financing approaches – willingness-to-pay,-borrow, and-work – and found that they significantly impact the prospects of achieving demand-driven cost recovery. The net benefit under willingness to work, in which water infrastructure is coupled to community irrigation and cash payments replaced by labor commitments, is impacted most strongly by groundwater yield and managerial factors. These findings suggest that the cost–benefit dynamics of groundwater-based water supply improvements vary considerably by many parameters, and that the relative strengths of different development strategies may be leveraged for achieving optimal outcomes.
Irrigation water salinity effects on colour and health ingredients in the pomegranate peel were s... more Irrigation water salinity effects on colour and health ingredients in the pomegranate peel were studied in two accessions, 'Wonderful' and 'SP-2', grown under a wide range of salinities, 1.2 to 9 dS m –1. Ripe fruit peels were analysed for phenolics and anthocyanins composition, and antioxidative capacity. Total phenolics concentration and antioxidative capacity were determined by the Folin-Ciocalteau and FRAP assays, respectively. Phenolics and anthocyanins composition was analysed by RP-HPLC. Increased salinity enhanced considerably the overall accumulation of phenolics and anthocyanins, and the antioxidative capacity in both cultivars; the magnitude of the effects was accession dependent. Mono-and di-glucosides of cyanidins, pelargonidins, and delphinidines were detected at proportions that varied with accession and salinity. Increased concentrations of gallotannins, flavonols and ellagic acid derivatives in 'Wonderful', and punicalagins, flavonols and ellagic acid derivatives in 'SP-2' accompanied elevated salinity levels. The results may benefit the pomegranate juice and byproduct valourisation industries, especially in the face of global water quality deterioration.
Notation A=cross-sectional area of flow (L 2 ); A z =volumetric cumulative infiltration per unit ... more Notation A=cross-sectional area of flow (L 2 ); A z =volumetric cumulative infiltration per unit length (L 3 /L); C=solute concentration (M/L 3 ); C 0 =constant solute concentration at furrow inlet (M/L 3 ); C i =initial solute concentration in the irrigation stream (M/L 3 ); h=pressure head (L); K(h)=unsaturated hydraulic conductivity function (L/T); K S =saturated hydraulic conductivity (L/T); K x =hydrodynamic (longitudinal) dispersion coefficient (L 2 /T); L=field length (L); Q=flow rate (L 3 /T); S e =effective saturation (-); S o =furrow longitudinal slope (-); Z=cumulative infiltration depth (L); b=width of flow (L); c u =dimensional constant for the Manning formula (L 1/2 /T); f c =a constant of the longitudinal dispersion function (-) ; k(L/T a ), a(-), and b(L/T)=parameters of the modified Kostiakov function;
Evaporation from the soil surface (E) can be a significant source of water loss in arid areas. In... more Evaporation from the soil surface (E) can be a significant source of water loss in arid areas. In sparsely vegetated systems, E is expected to be a function of soil, climate, irrigation regime, precipitation patterns, and plant canopy development and will therefore change dynamically at both daily and seasonal time scales. The objectives of this research were to quantify E in an isolated, drip-irrigated vineyard in an arid environment and to simulate below canopy E using the HYDRUS (2-D/3-D) model. Specific focus was on variations of E both temporally and spatially across the inter-row. Continuous above canopy measurements, made in a commercial vineyard, included evapotranspiration, solar radiation, air temperature and humidity, and wind speed and direction. Short-term intensive measurements below the canopy included actual and potential E and solar radiation along transects between adjacent vine-rows. Potential and actual E below the canopy were highly variable, both diurnally and with distance from the vine-row, as a result of shading and distinct wetted areas typical to drip irrigation. While the magnitude of actual E was mostly determined by soil water content, diurnal patterns depended strongly on position relative to the vine-row due to variable shading patterns. HYDRUS (2-D/3-D) successfully simulated the magnitude, diurnal patterns, and spatial distribution of E, including expected deviations as a result of variability in soil saturated hydraulic conductivity.
Since most people without access to safe water services live in remote areas of developing countr... more Since most people without access to safe water services live in remote areas of developing countries, assessing the economics of rural water developments poses a globally pressing challenge. This study seeks to: (1) outline the rural (non-networked) water development decision process in a systematic way; (2) incorporate that process into a modeling tool in order to conduct consistent economic analysis of developments across a wide range of contexts, and (3) assess the performance and potential applications of this tool. We introduce AWARE, a recently developed Decision Support System, to provide a generalized model of the processes and constraints related to the advancement of rural water services. AWARE enables robust comparisons to be made across a wide range of social, economic, physical, technical and management approaches. We demonstrate that it performs adequately, and propose that, despite its generalized approach, it will be useful for informing both development strategies and field projects.
During the summer, evaporative demand at midday often exceeds the transport capacity of most dese... more During the summer, evaporative demand at midday often exceeds the transport capacity of most desert plants. However, date palms maintain their ecological dominance with sustained and uniquely high rates of transpiration. This high rate of flow cannot be attributed to soil water supply alone. In order to quantify intra-plant water allocation in irrigated date palms, three water-sensing techniques have been incorporated: heat dissipation, gravimetric sampling, and time domain reflectrometry. Each of these methods has known limitations but their integration resulted in a quantitative in vivo accounting of the date palm diurnal and seasonal water mass balance. By incorporating these methods it was possible to determine that date palms substantially rely on the exploitation and recharge of the stem reservoir in their water budget. The stem of mature date palms can hold up to 1 m 3 of water and supply 25% of daily transpiration (i.e. 5000 l of water in 100 d of summer). The internal stem water reservoir is consistently recharged by over 50 l per night which allows for successive daytime reuse throughout the entire growing season. More broadly, these findings suggest that internal water allocation and night-time soil-water availability could provide useful information for improving date palm irrigation practices.
Efficient control of irrigation systems depends on attaining representative water status data for... more Efficient control of irrigation systems depends on attaining representative water status data for an irrigated field. The spatial variability of soil hydraulic properties and root growth patterns, hamper the use of single-value representations. This work proposes a two-pronged approach designed for determining optimal sensor location for irrigation water management. It combines experimental results, which offer a method of predetermining root growth patterns, with modeling analysis in which the effect of ten-siometer location on coefficient of variation (CV) of matric head measurements and irrigation system operation was investigated. In the experimental part, the effect of a geotextile material, wrapped around the drippers along the drip line to create a " Geotextile Drip Interface " (GDI), on root growth patterns in the field was evaluated. The results showed higher root density around the GDI vs. regular buried drippers, with well-defined peak root density in the former vs. no one location with peak root density in the latter. Genetic root architecture had smaller effect on root distribution under the GDI treatment. The modeling part consisted of HYDRUS 2D/3D simulations of high-frequency subsurface drip irrigation in heterogeneous soils with GDI root distribution as observed in the experiment. The simulations explored different locations for tensiometer placement which will result in low variability of system operation. HYDRUS 2D/3D simulations showed that the optimal location for tensiometer placement is near the subsurface dripper, resulting in low CV of matric head measurements and applied irrigation water, high sensitivity to irrigation, and lower drainage below the root zone. Overall, the results show that measuring soil water status with tensiometers located close to drippers in GDI volume, improve control of high frequency irrigation systems and allow greater water application efficiency in drip irrigated fields.
A B S T R A C T Irrigation is a service provided to agricultural crops in order to improve their ... more A B S T R A C T Irrigation is a service provided to agricultural crops in order to improve their yields. This is also a rare situation where the location of the costumers (roots) is not known and the heterogeneity in the water delivery system (soil) effects the water distribution. This non-uniformity of soil-plant conditions in the agricultural field complicates decision-making parameters regarding irrigation management (where to place sensors, how many sensors are needed, when and how much to irrigate). Many aspects of this non-uniformity have been studied in the past decades, including soil hydraulic properties, tillage history, irrigation method, sensor location, measured volume, and more. One aspect that has been relatively neglected is how plant roots affect variability. In this work, we focus on the effect that growing roots have on the variability of tensiometer measurements. Corn seeds were sown in a pre-designed experimental plot that consisted of three very distinct soils (sand, sandy loam, clay) to create high variation in investigated conditions. Subsurface drip irrigation was installed in the plot, and the drippers of the center line were wrapped with geotextile to create a geotextile-drip interface (GDI), i.e., a volume which has preferred conditions for root growth. Tensiometers were installed in the GDI (GDI treatment) and 10 cm away from the drip lines (S10 treatment); the matric head was monitored throughout the season. The weekly averaged coefficient of variation (CV) of the GDI treatment decreased as the corn plants grew, for each soil type and the entire plot. As time passed and the corn plants grew, CV peaks, due to irrigation, and the duration of high CV decreased because of the increasing influence of root water uptake on fluxes in the measured volume. After harvest, the CV returned to initial values. S10 tensiometers showed higher CV values than the GDI tensiometers during the last week of growth. After harvest, the CV of the S10 tensiometer measurements decreased, contrary to the trend in the GDI tensiometers. The results point to the major influence of roots on matric head variability, first, by decreasing variability with time and second, through the effect of tensiometer location since the GDI tensiometers were located in volumes with high root density. This influence has major consequences regarding the methodology of tensiometer measurements to represent an agricultural field, and might provide means for global guidelines for tensiometer placement and irrigation management.
The challenge of partitioning energy and evapotranspiration (ET) components was addressed over a ... more The challenge of partitioning energy and evapotranspiration (ET) components was addressed over a season (bud break till harvest) in a wine grape vineyard located in an extreme arid region. A below canopy energy balance approach was applied to continuously estimate evaporation from the soil (E) while system ET was measured using eddy covariance. Below canopy energy balance was assessed at the dry midrow position as well as the wet irrigated position directly underneath the vine row, with E calculated as the residual of measured net radiation, soil heat flux, and computed sensible heat flux. The variables used to compute sensible heat flux included soil surface temperature measured using infrared thermometers and below-canopy wind speed in a soil resistance formulation that required a modified wind factor. The E derived from below canopy energy balance was reasonable at daily intervals although it underestimated micro-lysimeter E measurements, suggesting there may have been advected energy from the midrow to the below-vine position. Seasonal partitioning indicated that total E amounted to 9–11% of ET. In addition, empirical functions from the literature relating crop coefficients (K cb) to plant size, appeared to give reasonable results under full canopy, albeit with some day to day variation, but underestimated K cb during the growing period.
To efficiently plan and deploy wireless sensor networks in palm orchards, it is crucial to obtain... more To efficiently plan and deploy wireless sensor networks in palm orchards, it is crucial to obtain preliminary knowledge of radio signal propagation and strength distribution characteristics. Various received signal strength indicator (RSSI) measurements were taken with antennas, operating with a 2.4-GHz band and located 0.05 m away from trunks. The RSSI measurements, at seven different antenna heights along one certain horizontal line, revealed that there were three distinct signal propagation characteristics resulting from the morphological features of the date palm trees. Compared with other heights, the attenuation rate was lower when the antennas were placed below the crown base due to the relative lack of obstacles in the propagation paths, which also provided good options for installing the antennas. In addition, offshoots had a slightly negative impact on signal propagation. Comparison analyses showed that the logarithm model was the most accurate and convenient of all the empirical signal attenuation models for predicting low power wireless signal propagation characteristics in date palm orchards. Further measurements were conducted to investigate the received signal strength distribution around individual trunks and between the orchards of different ages. Results indicated that the reliable communication range showed an increasing trend with increasing orchard age. Moreover, the trunks negatively impacted the signal propagation, and the interference strength depended on the position relationship among the trunks, the Tx and Rx antennas. Finally, the specific and detailed references were provided for the planning and deployment of wireless sensor networks in date palm orchards. Concluding remarks address potential future research.
Extreme temperature and drought stress are major environmental factors limiting agriculture world... more Extreme temperature and drought stress are major environmental factors limiting agriculture worldwide. A comprehensive understanding of plant behavior under different environmental conditions can be gained through experiments and through the application of biophysical crop models. This study presents a field experiment conducted with bean exposed to heat and drought stress. Based on an experimental data collection a crop model was set up, calibrated and validated. Hereby, the two different photosynthesis model approaches already implemented in the model, a simple empirical (the Goudriaan and van Laar or GvL model) and a biochemical photosynthesis model approach (the Farquhar-Ball-Collatz or FBC model), were tested. Both photosynthesis model approaches performed adequately under no stress conditions. Under heat stress conditions, yield was underestimated by both models. However, the FBC model performed better than the simpler photosynthesis model approach of the GvL model. The FBC crop model was able to predict the soil water dynamics, the plant growth and the stomatal conductance.
Roots play important roles in regulating whole-plant carbon and water relations in response to ex... more Roots play important roles in regulating whole-plant carbon and water relations in response to extreme soil temperature. Three foxtail millet (Setaria italica L.) lines (448-Ames 21521, 463-P1391643 and 523-P1219619) were subjected to two different soil temperatures (28 and 38 C). The gas exchange, chlorophyll fluorescence, root morphology and central metabolism of leaves and roots were studied at the grain-filling stage. High soil temperature (38 C) significantly influenced the shoot transpiration, sto-matal conductance, photosynthesis, root growth and metabolism of all lines. The root length and area were significantly reduced in lines 448 and 463 in response to the stress, while only a small non-specific reduction was observed in line 523 in response to the treatment. The shift of root metabolites in response to high soil temperature was also genotype specific. In response to high soil temperature, glutamate, proline and pyroglutamate were reduced in line 448, and alanine, aspartate, glycine, pyroglutamate, serine, threonine and valine were accumulated in line 463. In the roots of line 523, serine, threonine, valine, isomaltose, maltose, raffinose, malate and itaconate were accumulated. Root tolerance to high soil temperature was evident in line 523, in its roots growth potential, lower photosynthesis and stomatal conductance rates, and effective utilization and assimilation of membrane carbon and nitrogen, coupled with the accumulation of protective metabolites.
[1] Infiltration per unit area of the source region from discs, strips and furrows has previously... more [1] Infiltration per unit area of the source region from discs, strips and furrows has previously been shown to be the sum of the one-dimensional infiltration and an edge effect term. Here we apply the same approach to examine infiltration under a constant head from boreholes (both lined and unlined). A critical empirical parameter (g) in the edge effect term is related to the radius of the borehole, soil hydraulic properties, boundary and initial conditions. For lined boreholes, g has a narrow range and for the examples investigated, a constant value of 1.06 introduces less than 5% error compared to using the case-specific g value. For unlined boreholes, g is larger, ranging between 1.02 and 3.16 for the examples investigated, and should be estimated for specific conditions.
In many least developed countries, inadequate user willingness to pay (WTP) to achieve cost recov... more In many least developed countries, inadequate user willingness to pay (WTP) to achieve cost recovery for improvements to substandard rural water services is a major barrier to reaching targets such as the Millennium Development Goals. A meta-analysis of 21 contingent valuation studies conducted in least developed countries reveals that cost recovery from user demand is infeasible in most cases, and that rural areas are especially unwilling to pay enough to finance water service improvements. We argue that this is largely due to inability to pay cash rather than an absence of demand and propose two alternative financing approaches that may enable capital deficient communities to afford improvements. A discrete choice experiment, conducted in a rural catchment of Zambia, compares conventional cash-based WTP for different water service attributes with two alternative measures. (1) Willingness to borrow: Monthly payments in cash, with a no-interest loan given to the user. (2) Willingness to work: Instead of cash, payment in the form of contributing time devoted to unskilled labor. To different degrees, these alternatives elicit higher demand and enable cost recovery, providing evidence that demand-driven, economically sustainable water development efforts, as described here for Simango, Zambia, may be implemented for rural, resource-poor communities.
Plant and Soil, 2014
Background and aims In the Central Negev hills (Israel) many ancient terraced wadis exist, which ... more Background and aims In the Central Negev hills (Israel) many ancient terraced wadis exist, which captured runoff and caused gradual soil aggradation, which enabled agricultural practices. In these terraces, dark colored soil horizons were observed, containing charcoal, as can be found in Terra Preta soils, suggesting higher fertility compared to natural soils. The aim of our investigation was to investigate these anthropogenic soils and to study the effects of charcoal and ash addition on soil properties and crop growth. Methods We investigated 12 soil profiles, focusing on possible differences between light and dark colored soil horizons. We also investigated the effects of amendment Plant Soil of charcoal and ash on the growth of wheat (Triticum Aestivum L.) in a 40-day pot experiment involving two water regimes. Results Results show that charcoal content in light and dark horizons were both low (<0.2 %), but significantly lower bulk densities were found in dark colored horizons. In the crop experiment, charcoal addition resulted in decreased crop growth, while, in the water deficit regime, ash addition resulted in increased crop growth. Conclusions Considering the observed charcoal and the results from the crop experiment, we hypothesize that, in ancient run-off capturing agricultural systems, ash was purposefully added as fertilizer.
Journal of Irrigation and Drainage Engineering, 2009
Moment analysis techniques are applied to describe the spatial and temporal subsurface wetting pa... more Moment analysis techniques are applied to describe the spatial and temporal subsurface wetting patterns resulting from furrow infiltration and redistribution. These techniques are adapted from previous work with drip irrigation. The water added is considered as a "plume" with the zeroth moment representing the total volume of water applied to the domain. The first moments lead to the location of the center of the plume, and the second moments relate to the amount of spreading about the mean position. Using moments, any fraction of the applied water and its spatial extent, defined by an ellipse, can be related to a "probability" curve. Remarkably, the probability curves are, for practical purposes, identical for all times and for all of the soils considered in this study. The same observation was made in relation to the distribution of water under a dripper. The consistency of the probability relationships can be exploited to pinpoint the distribution of irrigation water under a furrow in a compact and physically meaningful way. This approach is tested with numerically generated data for infiltration from furrows in three contrasting soils. The general conclusion is that moment analysis allows a straightforward, physically meaningful description of the general pattern of moisture distribution. Potential applications of the results of moment analyses include improved irrigation management, formulation of the infiltration and redistribution process from a furrow in a neural network setting, and parameter estimation of the soil hydraulic properties.
Irrigation of crops in arid regions with marginal
water is expanding. Due to economic and environ... more Irrigation of crops in arid regions with marginal
water is expanding. Due to economic and environmental
issues arising from use of low-quality water, irrigation
should follow the actual crop water demands. However,
direct measurements of transpiration are scant, and indirect
methods are commonly applied; e.g., the Penman–Monteith
(PM) equation that integrates physiological and meteorological
parameters. In this study, the effects of environmental
conditions on canopy resistance and water loss were
experimentally characterized, and a model to calculate
palm tree evapotranspiration ETc was developed. A novel
addition was to integrate water salinity into the model, thus
accounting for irrigation water quality as an additional factor.
Palm tree ETc was affected by irrigation water salinity,
and maximum values were reduced by 25 % in plants
irrigated with 4 dS m−1 and by 50 % in the trees irrigated
with 8 dS m−1. Results relating the responses of stomata to the environment exhibited an exponential relation between
increased light intensities and stomatal conductance, a surprising
positive response of stomata to high vapor pressure
deficits and a decrease in conductance as water salinity
increased. These findings were integrated into a modified
‘Jarvis–PM’ canopy conductance model using only meteorological
and water quality inputs. The new approach produced
weekly irrigation recommendations based on field
water salinity (2.8 dS m−1) and climatic forecasts that led
to a 20 % decrease in irrigation water use when compared
with current irrigation recommendations.
It is commonly presumed that organic agriculture causes only minimal environmental pollution. In ... more It is commonly presumed that organic agriculture causes only minimal environmental pollution. In this study, we measured the quality of percolating water in the vadose zone, underlying both organic and conventional intensive greenhouses. Our study was conducted in newly established farms where the subsurface underlying the greenhouses has been monitored continuously from their establishment. Surprisingly , intensive organic agriculture relying on solid organic matter, such as composted manure that is implemented in the soil prior to planting as the sole fertilizer, resulted in significant down-leaching of nitrate through the vadose zone to the groundwater. On the other hand, similar intensive agriculture that implemented liquid fertilizer through drip irrigation , as commonly practiced in conventional agriculture, resulted in much lower rates of pollution of the vadose zone and groundwater. It has been shown that accurate fertilization methods that distribute the fertilizers through the irrigation system, according to plant demand, during the growing season dramatically reduce the potential for groundwater contamination from both organic and conventional greenhouses.
Aims Soil salinity can cause salt plant stress by reducing plant transpiration and yield due to v... more Aims Soil salinity can cause salt plant stress by reducing plant transpiration and yield due to very low osmotic potentials in the soil. For predicting this reduction, we present a simulation study to (i) identify a suitable functional form of the transpiration reduction function and (ii) to explain the different shapes of empirically observed reduction functions. Methods We used high resolution simulations with a model that couples 3D water flow and salt transport in the soil towards individual roots with flow in the root system. Results The simulations demonstrated that the local total water potential at the soil-root interface, i.e. the sum of the matric and osmotic potentials, is for a given root system, uniquely and piecewise linearly related to the transpiration rate. Using bulk total water potentials, i.e. spatially and temporally averaged potentials in the soil around roots, sigmoid relations were obtained. Unlike for the local potentials, the sigmoid relations were non-unique functions of the total bulk potential but depended on the contribution of the bulk osmotic potential. Conclusions To a large extent, Transpiration reduction is controlled by water potentials at the soil-root interface. Since spatial gradients in water potentials around roots are different for osmotic and matric potentials, depending on the root density and on soil hydraulic properties, transpiration reduction functions in terms of bulk water potentials cannot be transferred to other conditions, i.e. soil type, salt content, root density, beyond the conditions for which they were derived. Such a transfer could be achieved by downscaling to the soil-root interface using simulations with a high resolution process model.
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Papers by Naftali Lazarovitch
water is expanding. Due to economic and environmental
issues arising from use of low-quality water, irrigation
should follow the actual crop water demands. However,
direct measurements of transpiration are scant, and indirect
methods are commonly applied; e.g., the Penman–Monteith
(PM) equation that integrates physiological and meteorological
parameters. In this study, the effects of environmental
conditions on canopy resistance and water loss were
experimentally characterized, and a model to calculate
palm tree evapotranspiration ETc was developed. A novel
addition was to integrate water salinity into the model, thus
accounting for irrigation water quality as an additional factor.
Palm tree ETc was affected by irrigation water salinity,
and maximum values were reduced by 25 % in plants
irrigated with 4 dS m−1 and by 50 % in the trees irrigated
with 8 dS m−1. Results relating the responses of stomata to the environment exhibited an exponential relation between
increased light intensities and stomatal conductance, a surprising
positive response of stomata to high vapor pressure
deficits and a decrease in conductance as water salinity
increased. These findings were integrated into a modified
‘Jarvis–PM’ canopy conductance model using only meteorological
and water quality inputs. The new approach produced
weekly irrigation recommendations based on field
water salinity (2.8 dS m−1) and climatic forecasts that led
to a 20 % decrease in irrigation water use when compared
with current irrigation recommendations.
water is expanding. Due to economic and environmental
issues arising from use of low-quality water, irrigation
should follow the actual crop water demands. However,
direct measurements of transpiration are scant, and indirect
methods are commonly applied; e.g., the Penman–Monteith
(PM) equation that integrates physiological and meteorological
parameters. In this study, the effects of environmental
conditions on canopy resistance and water loss were
experimentally characterized, and a model to calculate
palm tree evapotranspiration ETc was developed. A novel
addition was to integrate water salinity into the model, thus
accounting for irrigation water quality as an additional factor.
Palm tree ETc was affected by irrigation water salinity,
and maximum values were reduced by 25 % in plants
irrigated with 4 dS m−1 and by 50 % in the trees irrigated
with 8 dS m−1. Results relating the responses of stomata to the environment exhibited an exponential relation between
increased light intensities and stomatal conductance, a surprising
positive response of stomata to high vapor pressure
deficits and a decrease in conductance as water salinity
increased. These findings were integrated into a modified
‘Jarvis–PM’ canopy conductance model using only meteorological
and water quality inputs. The new approach produced
weekly irrigation recommendations based on field
water salinity (2.8 dS m−1) and climatic forecasts that led
to a 20 % decrease in irrigation water use when compared
with current irrigation recommendations.