Performance Assessment of Thermal Infrared Cameras of Different Resolutions to Estimate Tree Water Status from Two Cherry Cultivars: An Alternative to Midday Stem Water Potential and Stomatal Conductance

Abstract

The midday stem water potential (Ψs) and stomatal conductance (gs) have been traditionally used to monitor the water status of cherry trees (Prunus avium L.). Due to the complexity of direct measurement, the use of infrared thermography has been proposed as an alternative. This study compares Ψs and gs against crop water stress indexes (CWSI) calculated from thermal infrared (TIR) data from high-resolution (HR) and low-resolution (LR) cameras for two cherry tree cultivars: ‘Regina’ and ‘Sweetheart’. For this purpose, a water stress–recovery cycle experiment was carried out at the post-harvest period in a commercial drip-irrigated cherry tree orchard under three irrigation treatments based on Ψs levels. The water status of trees was measured weekly using Ψs, gs, and compared to CWSIs, computed from both thermal cameras. Results showed that the accuracy in the estimation of CWSIs was not statistically significant when comparing both cameras for the representation of Ψs and gs in both cultivars. The performance of all evaluated physiological indicators presented similar trends for both cultivars, and the averaged differences between CWSI’s from both cameras were 11 ± 0.27%. However, these CWSI’s were not able to detect differences among irrigation treatments as compared to Ψs and gs.

Urban Green Infrastructure Monitoring Using Remote Sensing from Integrated Visible and Thermal Infrared Cameras Mounted on a Moving Vehicle

“…It is thought that the higher resolution from the FLIR camera will not impact with statistical significance results obtained with the low-cost camera system presented in this paper. The latter is supported by previous research that has compared different resolutions of visible and thermal infrared cameras for growth and water status assessment on trees with no significant differences for the parameters studied [ 39 , 64 ], which can be explained by the short height between the camera and the canopies included for these type of studies, which is between 3–5 m.…”

“…A tree water stress index (TWSI) was derived from the common crop water stress index (CWSI) [ 32 ] used in agriculture, which is a normalized value (0–1) and, therefore adimensional, and it was calculated using the following equation after determining T dry and T wet [ 44 ]: where T canopy is the actual canopy temperature extracted from the thermal image at determined positions, and T dry and T wet are the reference temperatures (in °C) obtained using the statistical temperature distribution discrimination described in published research [ 39 ].…”

“…This study has been based on the integration of previously developed technology from our research group for the automated analysis of visible and infrared thermal imagery for different crops such as eucalyptus trees [ 22 ], grapevines [ 32 , 33 , 34 , 35 ], kiwi plants [ 36 ], apple trees [ 37 ], cherry trees [ 38 , 39 , 40 ], and cocoa plants [ 41 ], among others.…”

Multivariate Analysis of a Wind–PV-Based Water Pumping Hybrid System for Irrigation Purposes

“…According to the Food and Agriculture Organization [92], Bulgaria was sixteenth in the world for cherry production in 2018 and twenty-first for wine (about 93% of the produced wine grapes are used for wine production [93]). The irrigation of these crops is very important for their quality [94,95], and for both cultures the drip irrigation method shows best results [96,97]. The irrigation norm for the crops is the same [98,99]-6 L/m 2 /daybut the periods of irrigation differ: 15 March to 1 September for cherries and 1 June to 1 September for wine grapes.…”

Monitoring and Mapping Vineyard Water Status Using Non-Invasive Technologies by a Ground Robot

“…However, if the transpiration process stops, because heat dissipation in the leaf no longer takes place, leaf temperature increases [13]. Thermal cameras of different resolution and prices [14], even smartphone-based [15], can be used as portable devices for the estimation of plant water status and to assist in the setup of irrigation schedules, but time and labor demand, together with the limited number of manual measurements are pitfalls that still remain. While the latter has been partially solved by aerial thermography, covering large field extensions [16], in some crops, such as grapevines, aerial observation provides thermal imagery in which pixels often mix canopy and soil information, which complicates further analyses as they need to be effectively separated.…”