Scientists in Brazil and Florida found that the direct examination of plant canopy temperature can assist in optimizing citrus irrigation management in greenhouses. The researchers were Gustavo Haddad Souza Vieira with the Federal Institute of Espírito Santo in Brazil and Rhuanito “Johnny” Ferrarezi with the University of Florida Institute of Food and Agricultural Sciences.
Their study aimed to develop a method to measure canopy temperature using thermal imaging in 1-year-old citrus plants in a greenhouse to identify plants with water stress and verify its potential to be used as a tool to assess citrus water status. The experiment was conducted for 48 days (Nov. 27, 2019 to Jan. 13, 2020).
The scientists evaluated the influence of five levels of irrigation on Red Ruby grapefruit and Valencia sweet orange. Images were taken using a portable thermal camera and analyzed using open-source software. The researchers determined canopy temperature, leaf photosynthesis and transpiration, and plant biomass.
Results indicated a positive relationship between the amount of water applied and the temperature response of plants exposed to different water levels. Grapefruit and sweet orange plants that received less water and were submitted to water restrictions showed higher canopy temperatures than air temperatures. The thermal images easily identified water-stressed plants.
The study can be used as a tool to assess citrus water status in 1-year-old citrus plants in greenhouses and perhaps in commercial operations with mature trees in the field.
This technique, coupled with an automated system, can be used for irrigation scheduling. Setting up a limit temperature is necessary to start the irrigation system and set the irrigation time based on the soil water content.
To use this process on a large scale, it is necessary to apply an automation routine to process the thermal images in real time and remove the weeds from the background to determine the canopy temperature.
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