Thermal imaging at plant level to assess the crop-water status in almond trees (cv. Guara) under deficit irrigation strategies

Almond (Prunus dulcis Mill. (D.A. Webb)) plantations in irrigated semi-arid areas need to successfully face the new scenarios of climate change combining sustainable irrigation strategies and tolerant cultivars to water stress. This work examines the response of young almond (cvs. Guara, Marta, and Lauranne) subjected to different irrigation doses under semi-arid conditions (South-West Spain). The trial was conducted during two seasons (2018–2019) with three irrigation strategies: A full-irrigated treatment (FI), which received 100% of the irrigation requirements (IR), and two sustained-deficit irrigation strategies that received 75% (SDI75) and 65% (SDI65) of IR. Crop water status was assessed by leaf water potential (Ψleaf) and stomatal conductance (gs) measurements, determining the yield response at the end of each season. Different physiological responses for the studied cultivars were observed, especially considering the Ψleaf measurements. In this way, cv. Marta behaved more tolerant, while cvs. Guara and Lauranne maintained higher gs rates in response to water stress. These differences were also observed in terms of yield. The cv. Lauranne did not reflect yield losses, and the opposite trend was observed for cv. Guara, in which reductions on fruit numbers per tree were detected. On overall, effective irrigation water savings (≈2100 m3·ha−1 in SDI65) could be feasible, although these responses are going to be substantially different, depending on the used cultivar.

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Unmanned Aerial Vehicle with Thermal Imaging for Automating Water Status in Vineyard

Journal of Electrical Engineering and Automation - September 2019 ◽

10.36548/jeea.2021.2.002 ◽

2021 ◽

Vol 3 (2) ◽

pp. 79-91

Author(s):

Subarna Shakya

Keyword(s):

High Resolution ◽

Water Level ◽

Unmanned Aerial Vehicle ◽

Thermal Imaging ◽

Water Status ◽

Water Levels ◽

Agricultural Crop ◽

Crop Water ◽

Crop Water Stress Index ◽

Aerial Vehicle

Thermal imaging is utilized as a technique in agricultural crop water management due to its efficiency in estimating canopy surface temperature and the ability to predict crop water levels. Thermal imaging was considered as a beneficial integration in Unmanned Aerial Vehicle (UAV) for agricultural and civil engineering purposes with the reduced weight of thermal imaging systems and increased resolution. When implemented on-site, this technique was able to address a number of difficulties, including estimation of water in the plant in farms or fields, while considering officially induced variability or naturally existing water level. The proposed effort aims to determine the amount of water content in a vineyard using the high-resolution thermal imaging. This research work has developed an unmanned aerial vehicle (UAV) that is particularly intended to display high-resolution images. This approach will be able to generate crop water stress index (CWSI) by utilizing a thermal imaging system on a clear-sky day. The measured values were compared to the estimated stomatal conductance (sg) and stem water (s) potential along the Vineyard at the same time. To evaluate the performance of the proposed work, special modelling approach was used to identify the pattern of variation in water level. Based on the observation, it was concluded that both ‘sg’ and ‘s’ value have correlated well with the CWSI value by indicating a great potential to monitor instantaneous changes in water level. However, based on seasonal changes in water status, it was discovered that the recorded thermal images did not correspond to seasonal variations in water status.

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Linking canopy temperature and trunk diameter fluctuations with other physiological water status tools for water stress management in citrus orchards

Functional Plant Biology ◽

10.1071/fp10202 ◽

2011 ◽

Vol 38 (2) ◽

pp. 106 ◽

Cited By ~ 32

Author(s):

Iván F. García-Tejero ◽

Víctor H. Durán-Zuazo ◽

José L. Muriel-Fernández ◽

Juan A. Jiménez-Bocanegra

Keyword(s):

Water Stress ◽

Deficit Irrigation ◽

Water Status ◽

Irrigation Treatment ◽

Canopy Temperature ◽

Control Treatment ◽

Stem Water Potential ◽

Crop Water ◽

Trunk Diameter ◽

Trunk Diameter Fluctuations

The continuous monitoring of crop water status is key to the sustainable management of water stress situations. Two deficit irrigation (DI) treatments were studied during the maximum evapotranspirative demand period in an orange orchard (Citrus sinensis (L.) Osb. cv. Navelina): sustained deficit irrigation irrigated at 55% crop evapotranspiration (ETC), and low-frequency deficit irrigation treatment, in which the plants were irrigated according to stem water potential at midday (Ψstem). Additionally, a control treatment irrigated at 100% of ETC was established. The daily canopy temperature (TC) was measured with an infrared thermometer camera together with measurements of trunk diameter fluctuations (TDF), Ψstem and stomatal conductance (gS). The time course of all physiological parameters and their relationships were analysed, confirming that canopy air temperature differential (TC – Ta) variations and TDF are suitable approaches for determining the water stress. In addition, the maximum daily shrinkage (MDS) and TC – Ta showed high sensitivity to water stress in comparison to Ψstem and gS. Significant relationships were found among MDS and TC – Ta with Ψstem and gS, for monitoring the crop water status by means of MDS vs Ψstem and TC – Ta vs Ψstem. Thus, the combination of these techniques would be useful for making scheduling decisions on irrigation in orchards with high variability in plant water stress.

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Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars

Agronomy ◽

10.3390/agronomy11071419 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1419

Author(s):

Saray Gutiérrez-Gordillo ◽

Javier de la Gala González-Santiago ◽

Emiliano Trigo-Córdoba ◽

Alfredo Emilio Rubio-Casal ◽

Iván Francisco García-Tejero ◽

...

Keyword(s):

Water Stress ◽

Deficit Irrigation ◽

Water Status ◽

Stress Conditions ◽

Irrigation Season ◽

Stem Water Potential ◽

Crop Water ◽

Regulated Deficit Irrigation ◽

Sensitive Periods ◽

Mild Water Stress

In recent years, the area dedicated to modern irrigated almond plantations has increased significantly in Spain. However, the legal irrigation allocations are lower than the maximum water requirements of the crop in most cases. Therefore, almond growers are forced to implement regulated deficit irrigation strategies on their farms, applying water stress in certain resistant phenological periods and avoiding it in sensitive periods. Given the need to monitor the water status of the crop, especially in the most sensitive periods to water stress, the objective of this work was to evaluate the sensitivity of two UAV-based crop water status indicators to detect early water stress conditions in four almond cultivars. The field trial was conducted during 2020 in an experimental almond orchard, where two irrigation strategies were established: full irrigation (FI), which received 100% of irrigation requirements (IR), and regulated deficit irrigation (RDI), which received 70% of IR during the whole irrigation period except during the kernel-filling stage when received 40% IR. The UAV flights were performed on four selected dates of the irrigation season. The Crop Water Status Index (CWSI) and the Normalized Difference Vegetation Index (NDVI) were derived from thermal and multispectral images, respectively, and compared to classical water status indicators, i.e., stem water potential (Ψstem), stomatal conductance (gs), and photosynthetic rate (AN). Of the four flights performed, three corresponded to mild water stress conditions and a single flight was performed under moderate water stress conditions. Under mild water stress, CWSI was not able to capture the differences between FI and RDI trees that were observed with Ψstem. Under moderate stress conditions, CWSI was sensitive to the water deficit reached in the trees and showed significant differences among both irrigation treatments. No differences were observed in the CWSI and NVDI response to water stress among cultivars. Although NDVI and CWSI were sensitive to water stress, the low signal intensity observed in NDVI makes this index less robust than CWSI to monitor crop water stress. It can be concluded that UAV-based CWSI measurements are reliable to monitor almond water status, although for early (mild) levels of water stress, Ψstem seems to be the preferred option.

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Assessing the Crop-Water Status in Almond (Prunus dulcis Mill.) Trees via Thermal Imaging Camera Connected to Smartphone

Sensors ◽

10.3390/s18041050 ◽

2018 ◽

Vol 18 (4) ◽

pp. 1050 ◽

Cited By ~ 16

Author(s):

Iván García-Tejero ◽

Carlos Ortega-Arévalo ◽

Manuel Iglesias-Contreras ◽

José Moreno ◽

Luciene Souza ◽

...

Keyword(s):

Thermal Imaging ◽

Water Status ◽

Prunus Dulcis ◽

Crop Water ◽

Thermal Imaging Camera ◽

Imaging Camera

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Assessing the Water-Stress Baselines by Thermal Imaging for Irrigation Management in Almond Plantations under Water Scarcity Conditions

Water ◽

10.3390/w12051298 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1298

Author(s):

Saray Gutiérrez-Gordillo ◽

Iván Francisco García-Tejero ◽

Víctor Hugo Durán Zuazo ◽

Amelia García Escalera ◽

Fernando Ferrera Gil ◽

...

Keyword(s):

Water Stress ◽

Thermal Imaging ◽

Water Status ◽

Irrigation Management ◽

Irrigation Treatment ◽

Canopy Temperature ◽

Irrigation Scheduling ◽

Stress Index ◽

Crop Water ◽

Crop Water Stress Index

This work examines the use of thermal imaging to determine the crop water status in young almond trees under sustained deficit irrigation strategies (SDIs). The research was carried out during two seasons (2018–2019) in three cultivars (Prunus dulcis Mill., cvs. Guara, Lauranne, and Marta) subjected to three irrigation treatments: a full irrigation treatment (FI) at 100% of irrigation requirements (IR), and two SDIs that received 75% and 65% of the IR, respectively. Crop water monitoring was done by measurements of canopy temperature, leaf water potential (Ψleaf), and stomatal conductance. Thermal readings were used to define the non-water-stress baselines (NWSB) and water-stress baselines (WSB) for each treatment and cultivar. According to our findings, Ψleaf was the most responsive parameter to reflect differences in almond water status. In addition, NWSB and WSB allowed the determination of the crop water-stress index (CWSI) and the increment of canopy temperature (ITC) for each SDI treatment, obtaining threshold values of CWSI (0.12–0.15) and ITC (~1 °C) that would ensure maximum water savings by minimizing the effects on yield. The findings highlight the importance of determining the different NWSB and WSB for different almond cultivars and its potential use for proper irrigation scheduling.

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Monitoring Crop Water Status and Irrigation Needs Using Multispectral Airborne Sensors

HortScience ◽

10.21273/hortsci.30.4.905d ◽

1995 ◽

Vol 30 (4) ◽

pp. 905D-905

Author(s):

Thomas R. Clarke ◽

M. Susan Moran

Keyword(s):

Water Stress ◽

Near Infrared ◽

Water Status ◽

Canopy Cover ◽

Stress Index ◽

Crop Water ◽

Vegetative Cover ◽

Crop Water Stress Index ◽

Water Stress Index ◽

Subsurface Drip

Water application efficiency can be improved by directly monitoring plant water status rather than depending on soil moisture measurements or modeled ET estimates. Plants receiving sufficient water through their roots have cooler leaves than those that are water-stressed, leading to the development of the Crop Water Stress Index based on hand-held infrared thermometry. Substantial error can occur in partial canopies, however, as exposed hot soil contributes to deceptively warm temperature readings. Mathematically comparing red and near-infrared reflectances provides a measure of vegetative cover, and this information was combined with thermal radiance to give a two-dimensional index capable of detecting water stress even with a low percentage of canopy cover. Thermal, red, and near-infrared images acquired over subsurface drip-irrigated cantaloupe fields demonstrated the method's ability to detect areas with clogged emitters, insufficient irrigation rate, and system water leaks.

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