Use of infrared thermography on canopies as indicator of water stress in ‘Arbequina’ olive orchards (original) (raw)
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An insight to the performance of crop water stress index for olive trees
Agricultural Water Management, 2013
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 would therefore be beneficial. Amongst 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. In an experiment conducted in a lysimeter facility in the northwestern Negev, Israel, irrigation was withheld for 6 days for 5 of 15 trees, while daily irrigation continued for the rest of the trees. After resuming irrigation, the trees were monitored for 5 additional days. Water status measurements and thermal imaging were conducted daily between 12:00 and 14:00. Diurnal monitoring (predawn to after dusk) of the same indicators was conducted on the day of maximum stress. Continuous meteorological data were acquired throughout the experimental period. Empirical and analytical CWSI were calculated based on canopy temperature extracted from thermal images. The empirical CWSI differentiated between well watered and stressed trees, and depicted the water status dynamics during the drought and recovery periods as well as on a diurnal scale. Analytical approaches did not perform as well at either time scale. In conclusion, the empirical CWSI seems to be 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. Practically, it is proposed to compute the wet temperature analytically and set the dry temperature to 5 • C higher than air temperature.
Irrigation Science, 2009
Irrigation of olive orchards is challenged to optimize both yields and oil quality. Best management practices for olive irrigation will likely depend on the ability to maintain mild to moderate levels of water stress during at least some parts of the growing season. We examined a number of soil, plant and remote sensing parameters for evaluating water stress in bearing olive (var. Barnea) trees in Israel. The trees were irrigated with five water application treatments (30, 50, 75, 100 and 125% of potential evapotranspiration) and the measurements of soil water content and potential, mid-day stem water potential, and stomatal resistance were taken. Remote thermal images of individual trees were used to alternatively measure average canopy temperature and to calculate the tree's crop water stress index (CWSI), testing empirical and analytical approaches. A strong non-linear response showing similar trends and behavior was evident in soil and plant water status measurements as well as in the CWSI, with decreasing rates of change at the higher irrigation application levels. No statistically significant difference was found between the analytical and the empirical CWSI, suggesting that the relative simplicity of the analytical method would make it preferable in practical applications.
Agricultural Water Management, 2017
Characterization of the spatio-temporal variability of tree water status is a prerequisite to conducting precise irrigation management in fruit tree orchards. This study assessed the suitability of a crop water stress index (CWSI) derived from high-resolution aerial thermal imagery for estimating tree water status variability in super high density (SHD) olive orchards. The experiment was conducted at a commercial SHD olive orchard near Seville (southwestern Spain), with drip irrigated trees under three irrigation treatments (four plots per treatment in a randomized block design): a full irrigation treatment to replace the crop water needs (ETc) and two regulated deficit irrigation treatments to replace ca. 45% of ETc. Meteorological variables, soil moisture content, leaf water potential, stem water potential and leaf gas exchange measurements were performed along the irrigation season. Infrared temperature sensors (IRTs) installed approximately 1 m above the canopies were used to derive the required Non-Water-Stressed Baselines Postprint of: Agricultural Water Management (187) 210-221 (2017) 2 (NWSBs) for CWSI calculation. NWSBs were not common during the growing season, although the seasonal effect could be partly explained with solar angle variations. A thermal camera installed on a mini Remotely Piloted Aircraft System (RPAS) allowed for the recording of high-resolution thermal images on representative dates during the irrigation season. The CWSI values derived from aerial thermal imagery were sensitive to the imposed variations in tree water status within the SHD olive orchard. Among the recorded variables, maximum stomatal conductance showed the tightest correlation with CWSI. We concluded that high-resolution thermal imagery captured from a mini RPAS is a suitable tool for defining tree water status variability within SHD olive orchards.
Detection of water stress in an olive orchard with thermal remote sensing imagery
Agricultural and Forest Meteorology, 2006
An investigation of the detection of water stress in non-homogeneous crop canopies such as orchards using high-spatial resolution remote sensing thermal imagery is presented. An airborne campaign was conducted with the Airborne Hyperspectral Scanner (AHS) acquiring imagery in 38 spectral bands in the 0.43-12.5 mm spectral range at 2.5 m spatial resolution. The AHS sensor was flown at 7:30, 9:30 and 12:30 GMT in 25 July 2004 over an olive orchard with three different water-deficit irrigation treatments to study the spatial and diurnal variability of temperature as a function of water stress. A total of 10 AHS bands located within the thermal-infrared region were assessed for the retrieval of the land surface temperature using the split-window algorithm, separating pure crowns from shadows and sunlit soil pixels using the reflectance bands. Ground truth validation was conducted with infrared thermal sensors placed on top of the trees for continuous thermal data acquisition. Crown temperature (T c ), crown minus air temperature (T c À T a ), and relative temperature difference to well-irrigated trees (T c À T R , where T R is the mean temperature of the well-irrigated trees) were calculated from the ground sensors and from the AHS imagery at the crown spatial resolution. Correlation coefficients for T c À T R between ground IRT sensors and airborne image-based AHS estimations were R 2 = 0.50 (7:30 GMT), R 2 = 0.45 (9:30 GMT) and R 2 = 0.57 (12:30 GMT). Relationships between leaf water potential and crown T c À T a measured with the airborne sensor obtained determination coefficients of R 2 = 0.62 (7:30 GMT), R 2 = 0.35 (9:30 GMT) and R 2 = 0.25 (12:30 GMT). Images of T c À T a and T c À T R for the entire field were obtained at the three times during the day of the overflight, showing the spatial and temporal distribution of the thermal variability as a function of the water deficit irrigation schemes. #
Plant water status is an important factor to be quickly and accurately assessed temporally and spatially to maintain yield and quality standards in a changing environment. The pressure chamber is the most common method to measure midday stem water potential (MSWP), which is used as an accurate indicator of plants water status. However, the use of the latter method has the disadvantages of being manual, destructive, slow and impractical to have a good spatial representation of plant water status of a whole olive orchard. The objective of this research was to test an indirect method to estimate MSWP using visible and near infrared (NIR) spectroscopy analysis. This method is non-destructive and quick to implement in the field having the extra advantage of assessing the whole tree with a single measurement using short-range remote sensing. In this study, MSWP was measured using a pressure chamber (PMS Instrument Co. USA) to characterize water status of olive trees in a commercial drip-irrigated 'Arbequina' orchard (Pencahue, Region del Maule, Chile). Canopy reflectance was measured between 350 and 2500 nm wavelength region with a spectrometer FieldSpect3 (Analytical Spectral Device, ASD Co., USA) from 2.5 m distance. The spectroscopy analysis was done using partial least squares (PLS) regression by the Unscramble software. The validation process showed a root mean square error (RMSE) equal to 0.88 MPa and coefficient of determination (R 2 ) equal to 0.75. These results showed that the noninvasive method, using spectral reflectance data, could obtain a surrogate of stem water potential of olive trees, providing the possibility to screen more samples under field conditions and to automate the data gathering and analysis once a calibration curve is developed.
Horticulturae
The transversal fruit diameter (FD) was monitored continuously by automatic extensimeters (fruit gauges) in order to monitor fruit growth dynamics under deficit irrigation treatments. The daily diameter fluctuation (ΔD, mm), the daily growth (ΔG, mm), the cumulative fruit growth (CFG, mm), and the fruit relative growth rate (RGR, mm mm−1 h−1) of four olive cultivars (Ascolana dura, Piantone di Falerone, Arbequina, and Lea) were studied during the third phase of fruit growth. Two regulated deficit irrigation treatments DI-20 (20% of ETc) and DI-10 (10% of ETc) were applied. The daily hysteretic pattern of FD versus the environmental variable of vapor pressure deficit (VPD) was evaluated using the data of a local weather station. The assessment of fruit growth parameters showed cultivar-specific response to water stress. For instance, after performing deficit irrigation, minimum RGR in different cultivars downsized with various slopes which suggested a very different response of the c...
Horticulturae
The irrigation surface of olive orchards has increased over recent decades. In zones affected, deficit irrigation scheduling is a must. The aim of this work was to study water stress management based on reference equations for midday stem water potential. An experiment was conducted over three seasons in Seville (Spain) from 2020 to 2022. A young hedgerow olive orchard (cv Manzanilla de Sevilla) was irrigated using three different treatments: Control (full irrigated), RDI, and Rainfed, in a completely randomized design (six replications). The midday stem water potential and leaf conductance were measured throughout the three seasons. Stem water potential was more sensitive to water stress than leaf conductance and showed a clearer impact and rehydration. Individual data of stem water potential were grouped according to leaf conductance reduction. The relationship of these stem water potentials and temperature or vapor pressure deficit was significant, linear, and aligned to publishe...
Spatial distribution of water status in irrigated olive orchard by thermal imaging
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