Agricultural research is conducted towards improving efficiency and quality
Current projects
Remote sensing of wine-grapevine transpiration for improving vine water status
High-value wine-grape production is managed to enhance fruit quality via deficit irrigation, even at the expense of reduced yield. These management strategies are strongly dependent on accurate estimates of the amount and timing of water delivery to the vines to achieve appropriate stress levels at the desired time. Control of vine water status can be achieved by monitoring vineyard water balance, and accurate estimates of evapotranspiration (ET) are a critical component of this approach. Since the vine transpiration (T) component of ET will more closely reflect the water status of the vines, irrigation management would benefit from an accurate determination of the unique contribution of T to the total vineyard water use. The overarching goal of this research is to reliably map T from wine-grape vineyards across a large range of climatic conditions by adapting remote sensing-based tools and models. We hypothesize that better estimation of leaf area index (LAI) and biomass distribution of the vine canopy, will enhance the internal separation of plant and soil water fluxes in the TSEB model and will enhance the utility of the modified wind and radiation extinction algorithms developed for vineyards, ultimately resulting in more accurate T estimates.
High-value wine-grape production is managed to enhance fruit quality via deficit irrigation, even at the expense of reduced yield. These management strategies are strongly dependent on accurate estimates of the amount and timing of water delivery to the vines to achieve appropriate stress levels at the desired time. Control of vine water status can be achieved by monitoring vineyard water balance, and accurate estimates of evapotranspiration (ET) are a critical component of this approach. Since the vine transpiration (T) component of ET will more closely reflect the water status of the vines, irrigation management would benefit from an accurate determination of the unique contribution of T to the total vineyard water use. The overarching goal of this research is to reliably map T from wine-grape vineyards across a large range of climatic conditions by adapting remote sensing-based tools and models. We hypothesize that better estimation of leaf area index (LAI) and biomass distribution of the vine canopy, will enhance the internal separation of plant and soil water fluxes in the TSEB model and will enhance the utility of the modified wind and radiation extinction algorithms developed for vineyards, ultimately resulting in more accurate T estimates.
Can combining photovoltaic power production with Jojoba plantation be win-win?
Population growth and the rising need for renewable energy on the one hand, and the lack of available land on the other hand, sharpens and increases the need for agro-photovoltaic systems that enable dual use of land, for electricity production and agricultural cultivation. We examine this combination will be examined in jojoba plantations. The rapid increase in the volume of jojoba plantings in Israel and in the world, and the limited market have led to a drop in prices, so the possibility of increasing the profit from the existing plots by adding electricity generation in the areas and creating a dual use interface on the land, will allow the growers to get through the next difficult years in which the profitability of the cultivation be low. Given the typical hot and dry conditions in areas where jojoba grows, mid-day stomatal closure results in assimilation occurring mostly on the east facing side of the canopy exposed to sunlight in the morning. A thoughtful installation of photovoltaic systems may reduce heat stress and allow longer hours during which stomata are open, ultimately increasing photosynthesis.
Population growth and the rising need for renewable energy on the one hand, and the lack of available land on the other hand, sharpens and increases the need for agro-photovoltaic systems that enable dual use of land, for electricity production and agricultural cultivation. We examine this combination will be examined in jojoba plantations. The rapid increase in the volume of jojoba plantings in Israel and in the world, and the limited market have led to a drop in prices, so the possibility of increasing the profit from the existing plots by adding electricity generation in the areas and creating a dual use interface on the land, will allow the growers to get through the next difficult years in which the profitability of the cultivation be low. Given the typical hot and dry conditions in areas where jojoba grows, mid-day stomatal closure results in assimilation occurring mostly on the east facing side of the canopy exposed to sunlight in the morning. A thoughtful installation of photovoltaic systems may reduce heat stress and allow longer hours during which stomata are open, ultimately increasing photosynthesis.
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The Grape Remote sensing Atmospheric Profile & Evapotranspiration eXperiment
Proud to be part of the core group of this project! The mission of GRAPEX is to refine and apply a multi-scale remote sensing evapotranspiration (ET) toolkit for mapping crop water use and crop stress for improved irrigation scheduling and water management in vineyards in the Central Valley of California, a region of endemic periodic drought. While this work will focus primarily on vineyards, the improved tools will also have applications to fruit and nut orchards and other crops with highly-structured canopies. |
Watch this 2-minute video to learn more
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Past projects
Two Source Energy Balance (TSEB) model estimates of transpiration and soil water evaporation
Accurate estimates of evapotranspiration (ET) with remotely sensed data has the potential to help determine irrigation requirements based on water status across large surface areas. Separation of ET into plant transpiration (T) and soil water evaporation (E) gives additional insight into irrigation efficiency as well as plant growth and associated carbon exchange. The TSEB model estimates ET by solving the energy balances for soil and canopy components using surface temperature, leaf area index, and weather data. With advances in remote sensing, estimates of surface temperature and leaf area index are becoming available at higher temporal and spatial resolution. This allows for increasingly more accurate ET estimates over large areas. However, while TSEB ET estimates have been successfully validated over a variety of crop types, the partitioning into E and T has not been fully assessed. The aim of this project is to evaluate not only TSEB estimates of ET but also ET partitioning using previously collected soil and canopy energy balance data over a vineyard. Model performance and potential improvements are tested as ET partitioning changes with plant growth and through irrigation and drying cycles.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA
Accurate estimates of evapotranspiration (ET) with remotely sensed data has the potential to help determine irrigation requirements based on water status across large surface areas. Separation of ET into plant transpiration (T) and soil water evaporation (E) gives additional insight into irrigation efficiency as well as plant growth and associated carbon exchange. The TSEB model estimates ET by solving the energy balances for soil and canopy components using surface temperature, leaf area index, and weather data. With advances in remote sensing, estimates of surface temperature and leaf area index are becoming available at higher temporal and spatial resolution. This allows for increasingly more accurate ET estimates over large areas. However, while TSEB ET estimates have been successfully validated over a variety of crop types, the partitioning into E and T has not been fully assessed. The aim of this project is to evaluate not only TSEB estimates of ET but also ET partitioning using previously collected soil and canopy energy balance data over a vineyard. Model performance and potential improvements are tested as ET partitioning changes with plant growth and through irrigation and drying cycles.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA
Row orientation affects the momentum flux in wine grapevines
The momentum flux affects the energy exchange processes and thus may indirectly affect the water balance of agricultural fields. In wine vineyards, a high momentum flux between the vine rows may augment the evaporation and transpiration fluxes, and therefore decrease the water use efficiency. On the other hand, at night, high momentum fluxes may reduce (or even prevent) the formation of dew on the vine canopy, thus decrease the potential development of fungi and related diseases. We hypothesized that the wind direction relative to the row orientation in largely-spaced narrow hedge-rows characterizing wine vineyards greatly affects the momentum flux. This, in turn affects the vineyard microclimate, and ultimately, the grape quality. The objective of our research was to assess the effect of row orientation on the momentum fluxes in wine grapevines.
The momentum flux affects the energy exchange processes and thus may indirectly affect the water balance of agricultural fields. In wine vineyards, a high momentum flux between the vine rows may augment the evaporation and transpiration fluxes, and therefore decrease the water use efficiency. On the other hand, at night, high momentum fluxes may reduce (or even prevent) the formation of dew on the vine canopy, thus decrease the potential development of fungi and related diseases. We hypothesized that the wind direction relative to the row orientation in largely-spaced narrow hedge-rows characterizing wine vineyards greatly affects the momentum flux. This, in turn affects the vineyard microclimate, and ultimately, the grape quality. The objective of our research was to assess the effect of row orientation on the momentum fluxes in wine grapevines.
Variability in below canopy radiation in wine vineyards
Vineyards canopy architecture and row structure pose unique challenges in modeling the radiation partitioning and energy exchange between the vine canopy and the interrow area. Here we aim to estimate the intercepted radiation by the canopy, and the effect of this interception on the below-canopy surface energy balance and evapotranspiration (ET). Measurements are conducted in a vineyard in CA as part of the Grape Remote sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX).
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA and colleagues, as part of the GRAPEX project.
Vineyards canopy architecture and row structure pose unique challenges in modeling the radiation partitioning and energy exchange between the vine canopy and the interrow area. Here we aim to estimate the intercepted radiation by the canopy, and the effect of this interception on the below-canopy surface energy balance and evapotranspiration (ET). Measurements are conducted in a vineyard in CA as part of the Grape Remote sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX).
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA and colleagues, as part of the GRAPEX project.
Micro‑scale spatial variability in soil heat flux in a wine‑grape vineyard
In vineyards, hourly soil heat flux (SHF) may account for as much as 30% of net radiation. Therefore, inaccurate estimates of SHF may lead to non-negligible errors when quantifying the surface energy balance. The typical canopy height to width ratio of two along with widely spaced rows (row spacing exceeding canopy height), and leaf biomass concentrated in the upper half of the vine canopy result in variable shading conditions producing sharp, sometimes abrupt, differences in SHF between adjacent points within the interrow space. Drip irrigation, which is also a typical practice in many vineyards in semi-arid regions, adds an additional source of variability in the interrow soil moisture which strongly affects SHF. Lastly, the common practice in Californian wine-grape vineyards to plant cover crop in the interrow, forming two distinct areas below the canopy—bare soil and crop cover, further increases SHF variability in the interrow. This small-scale variability challenges the measurement of SHF in such agrosystems. The objective of the research is to assess the micro-scale (within the interrow between two vine rows) spatial variability in SHF, and to determine which of the three variables—non-uniform (in both space and time) shading patterns, non-uniform surface cover (bare soil vs. cover crop) and non-uniform soil water content (due to the drip irrigation)—is the most significant driver for the local heterogeneity.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA and colleagues, as part of the GRAPEX project.
In vineyards, hourly soil heat flux (SHF) may account for as much as 30% of net radiation. Therefore, inaccurate estimates of SHF may lead to non-negligible errors when quantifying the surface energy balance. The typical canopy height to width ratio of two along with widely spaced rows (row spacing exceeding canopy height), and leaf biomass concentrated in the upper half of the vine canopy result in variable shading conditions producing sharp, sometimes abrupt, differences in SHF between adjacent points within the interrow space. Drip irrigation, which is also a typical practice in many vineyards in semi-arid regions, adds an additional source of variability in the interrow soil moisture which strongly affects SHF. Lastly, the common practice in Californian wine-grape vineyards to plant cover crop in the interrow, forming two distinct areas below the canopy—bare soil and crop cover, further increases SHF variability in the interrow. This small-scale variability challenges the measurement of SHF in such agrosystems. The objective of the research is to assess the micro-scale (within the interrow between two vine rows) spatial variability in SHF, and to determine which of the three variables—non-uniform (in both space and time) shading patterns, non-uniform surface cover (bare soil vs. cover crop) and non-uniform soil water content (due to the drip irrigation)—is the most significant driver for the local heterogeneity.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA and colleagues, as part of the GRAPEX project.
Manipulating bunch microclimate to enhance grape quality in arid environments
The distinct taste of wine is the result of an interplay between multiple plant endogenous and environmental factors, as well as fermentation and wine processing. In arid regions, the combined effect of high leaf-to-air vapor pressure gradients and high temperature are known to limit grapevine yield, negatively affecting berry development and metabolism. Over-exposure of the cluster is a common phenomenon, which can lead to sun-burn and degradation of quality-related secondary metabolites. On the other hand, there is evidence that berries that develop in open canopy conditions, as opposed to those develop in shaded canopy conditions, have higher juice sugar concentration, improved acid balance, fewer incidences of unripe herbaceous fruit characters, and often increased concentration of berry phenolics, including anthocyanins. Many environmental stresses are known to affect the synthesis of desired metabolites in the berry’s skin. However defining the most appropriate fruit conditions for yielding best grape quality is not trivial and experimentally challenging. The long-term aim of this research is to define a set of optimal viticulture practices to improve grape berry quality in semiarid environments by manipulating the bunch micro climate, and elucidating their association with the berry chemical composition.
--In collaboration with Aaron Fait, Ben-Gurion University of the Negev, Israel
The distinct taste of wine is the result of an interplay between multiple plant endogenous and environmental factors, as well as fermentation and wine processing. In arid regions, the combined effect of high leaf-to-air vapor pressure gradients and high temperature are known to limit grapevine yield, negatively affecting berry development and metabolism. Over-exposure of the cluster is a common phenomenon, which can lead to sun-burn and degradation of quality-related secondary metabolites. On the other hand, there is evidence that berries that develop in open canopy conditions, as opposed to those develop in shaded canopy conditions, have higher juice sugar concentration, improved acid balance, fewer incidences of unripe herbaceous fruit characters, and often increased concentration of berry phenolics, including anthocyanins. Many environmental stresses are known to affect the synthesis of desired metabolites in the berry’s skin. However defining the most appropriate fruit conditions for yielding best grape quality is not trivial and experimentally challenging. The long-term aim of this research is to define a set of optimal viticulture practices to improve grape berry quality in semiarid environments by manipulating the bunch micro climate, and elucidating their association with the berry chemical composition.
--In collaboration with Aaron Fait, Ben-Gurion University of the Negev, Israel
Advection in an isolated drip-irrigated wine vineyard in the desert
Vineyards are increasingly cultivated in arid areas, and while traditionally rain-fed, under arid conditions, irrigation is indispensable. Evapotranspiration in irrigated fields in arid environments can be enhanced by advection of sensible heat from the dry areas outside the vineyard, as well as from dry areas within the field. The aim of this research is to understand how local and within field advection affects the energy balance of the vineyard.
Vineyards are increasingly cultivated in arid areas, and while traditionally rain-fed, under arid conditions, irrigation is indispensable. Evapotranspiration in irrigated fields in arid environments can be enhanced by advection of sensible heat from the dry areas outside the vineyard, as well as from dry areas within the field. The aim of this research is to understand how local and within field advection affects the energy balance of the vineyard.
Optimizing water harvesting systems
For thousands of years man in arid environments has tried to skillfully manage the scarce water resource by collecting runoff water and utilizing it for irrigation. Water harvesting methods formerly developed for mere existence are nowadays receiving renewed attention. Micro-catchment water harvesting systems, used in many dryland areas around the world, are systems by which runoff is being collected from a contributing area and stored for consumptive use in the root zone of an adjacent infiltration basin. Conservation of harvested water by minimizing losses mainly involves reducing direct evaporation. Traditionally, the infiltration basins of micro-catchment systems were at the surface level. It is proposed that by replacing the shallow infiltration basin with a trench, the amount of harvested water will not change, but due to the reduced evaporating surface and the attenuation of solar radiation reaching down to the trench floor, the evaporative loss will largely decrease. Under similar soil and meteorological conditions, the most dominant factor determining the amount of evaporation from the infiltration basin is solar radiation. The overall objective of this research is to optimally design the trench dimensions and orientation for minimizing solar radiation load by modeling the radiation reaching trenches at various configurations of size and orientation.
For thousands of years man in arid environments has tried to skillfully manage the scarce water resource by collecting runoff water and utilizing it for irrigation. Water harvesting methods formerly developed for mere existence are nowadays receiving renewed attention. Micro-catchment water harvesting systems, used in many dryland areas around the world, are systems by which runoff is being collected from a contributing area and stored for consumptive use in the root zone of an adjacent infiltration basin. Conservation of harvested water by minimizing losses mainly involves reducing direct evaporation. Traditionally, the infiltration basins of micro-catchment systems were at the surface level. It is proposed that by replacing the shallow infiltration basin with a trench, the amount of harvested water will not change, but due to the reduced evaporating surface and the attenuation of solar radiation reaching down to the trench floor, the evaporative loss will largely decrease. Under similar soil and meteorological conditions, the most dominant factor determining the amount of evaporation from the infiltration basin is solar radiation. The overall objective of this research is to optimally design the trench dimensions and orientation for minimizing solar radiation load by modeling the radiation reaching trenches at various configurations of size and orientation.
Evapotranspiration partitioning –
measurement methods
Soil evaporation (E) can be a significant component of the water budget of sparsely vegetated crops in arid areas where evapotranspiration (ET) typically accounts for >95% of the water budget. Evapotranspiration has long been one of the key interests in agriculture, as it continues to be one of the best estimates for biomass production and yield. Irrigation amounts are adjusted according to pre-computed potential ET values for specific crops. Today, there is a specific focus on reducing water application without reducing plant production, and therefore, differentiating between soil evaporation (E) and transpiration (T) is becoming more and more relevant. This is particularly valid for row crops and other sparse crops where soil is exposed under the plant canopy. Due to the complexity of soil and plant interactions, coupled with changes in atmospheric and soil water content conditions, this field still has a lot of opportunity for exploration. Quantification of the E component using measurements is challenging. Approaches include both direct measurements and measurements of water and/or energy balance components in order to calculate E and theoretical modeling approaches to predict E based on climate, soil and plant conditions. Direct measurement of E is, to date, the largest challenge to those addressing the issue.
--In collaboration with Josh Heitman, NC State University, NC, USA; Tom Sauer, USDA Agricultural Research Services, IA, USA; Alon Ben-Gal, Gilat Research Center, Agricultural Research Organization, Israel.
measurement methods
Soil evaporation (E) can be a significant component of the water budget of sparsely vegetated crops in arid areas where evapotranspiration (ET) typically accounts for >95% of the water budget. Evapotranspiration has long been one of the key interests in agriculture, as it continues to be one of the best estimates for biomass production and yield. Irrigation amounts are adjusted according to pre-computed potential ET values for specific crops. Today, there is a specific focus on reducing water application without reducing plant production, and therefore, differentiating between soil evaporation (E) and transpiration (T) is becoming more and more relevant. This is particularly valid for row crops and other sparse crops where soil is exposed under the plant canopy. Due to the complexity of soil and plant interactions, coupled with changes in atmospheric and soil water content conditions, this field still has a lot of opportunity for exploration. Quantification of the E component using measurements is challenging. Approaches include both direct measurements and measurements of water and/or energy balance components in order to calculate E and theoretical modeling approaches to predict E based on climate, soil and plant conditions. Direct measurement of E is, to date, the largest challenge to those addressing the issue.
--In collaboration with Josh Heitman, NC State University, NC, USA; Tom Sauer, USDA Agricultural Research Services, IA, USA; Alon Ben-Gal, Gilat Research Center, Agricultural Research Organization, Israel.
Evapotranspiration partitioning –
modeling approaches
Understanding of water and energy dynamics of agricultural crops is important for developing new tools and improving management practices. To be adopted for operational use, these tools need to be reliable, easy to use, and cost effective. While some of the existing measurement methods provide reliable estimates of water and energy fluxes and are widely used, their cost and operational requirements limit their utility to research applications. Models that require minimal amount of input data from which accurate ET estimates can be derived are highly desirable. We work towards achieving this goal in two directions. (1) HYDRUS - describes the soil water and energy movement in the uppermost soil layer and provides local scale estimates. (2) Two source energy balance (TSEB) - utilizes thermal remote sensing data to describe the energy exchange across the soil-plant-atmosphere continuum, focusing of the above ground dynamics, from which spatially distributed ET maps are derived, at field, landscape, and regional.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA
modeling approaches
Understanding of water and energy dynamics of agricultural crops is important for developing new tools and improving management practices. To be adopted for operational use, these tools need to be reliable, easy to use, and cost effective. While some of the existing measurement methods provide reliable estimates of water and energy fluxes and are widely used, their cost and operational requirements limit their utility to research applications. Models that require minimal amount of input data from which accurate ET estimates can be derived are highly desirable. We work towards achieving this goal in two directions. (1) HYDRUS - describes the soil water and energy movement in the uppermost soil layer and provides local scale estimates. (2) Two source energy balance (TSEB) - utilizes thermal remote sensing data to describe the energy exchange across the soil-plant-atmosphere continuum, focusing of the above ground dynamics, from which spatially distributed ET maps are derived, at field, landscape, and regional.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA
Develop an algorithm for sharpening thermal imagery (TsHARP)
High spatial resolution (~100 m) thermal infrared band imagery has utility in a variety of applications in environmental monitoring. However, currently such data have limited availability and only at low temporal resolution, while coarser resolution thermal data (~1000 m) are routinely available, but not as useful for identifying environmental features for many landscapes. An algorithm for sharpening thermal imagery (TsHARP) to higher resolutions typically associated with the shorter wavebands (visible and near-infrared) was examined. This algorithm is based on the assumption that a unique relationship between radiometric surface temperature (TR) relationship and vegetation index (VI) exists at multiple resolutions. Four different methods for defining a VI-TR basis function for sharpening were examined, and an optimal form involving a transformation to fractional vegetation cover was identified.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA
High spatial resolution (~100 m) thermal infrared band imagery has utility in a variety of applications in environmental monitoring. However, currently such data have limited availability and only at low temporal resolution, while coarser resolution thermal data (~1000 m) are routinely available, but not as useful for identifying environmental features for many landscapes. An algorithm for sharpening thermal imagery (TsHARP) to higher resolutions typically associated with the shorter wavebands (visible and near-infrared) was examined. This algorithm is based on the assumption that a unique relationship between radiometric surface temperature (TR) relationship and vegetation index (VI) exists at multiple resolutions. Four different methods for defining a VI-TR basis function for sharpening were examined, and an optimal form involving a transformation to fractional vegetation cover was identified.
--In collaboration with William P. Kustas, USDA Agricultural Research Services, Beltsville, MD, USA
Assessing olive tree water status with the Crop Water Stress Index (CWSI)
Optimization of olive oil quantity and quality requires finely tuned water management, as increased irrigation, up to a certain level, results in increasing yield, but a certain degree of stress improves oil quality. Monitoring tools that provide accurate information regarding orchard water status are therefore beneficial. Among the various existing methods, those having high resolution, either temporally (i.e., continuous) or spatially, have the maximum adoption potential. One of the commonly used spatial methods is the Crop Water Stress Index (CWSI). The objective of this research was to test the ability of the CWSI to characterize water status dynamics of olive trees as they enter into and recover from stress, and on a diurnal scale. CWSI was tested in an empirical form and in two analytical configurations, all based on canopy temperature extracted from thermal images. The empirical CWSI was found promising even given its limitations, while analytical forms of CWSI still require improvement before they can be used as a water status monitoring tool for olive orchards.
--In collaboration with Alon Ben-Gal, Gilat Research Center, Agricultural Research Organization, Israel.
Optimization of olive oil quantity and quality requires finely tuned water management, as increased irrigation, up to a certain level, results in increasing yield, but a certain degree of stress improves oil quality. Monitoring tools that provide accurate information regarding orchard water status are therefore beneficial. Among the various existing methods, those having high resolution, either temporally (i.e., continuous) or spatially, have the maximum adoption potential. One of the commonly used spatial methods is the Crop Water Stress Index (CWSI). The objective of this research was to test the ability of the CWSI to characterize water status dynamics of olive trees as they enter into and recover from stress, and on a diurnal scale. CWSI was tested in an empirical form and in two analytical configurations, all based on canopy temperature extracted from thermal images. The empirical CWSI was found promising even given its limitations, while analytical forms of CWSI still require improvement before they can be used as a water status monitoring tool for olive orchards.
--In collaboration with Alon Ben-Gal, Gilat Research Center, Agricultural Research Organization, Israel.