New system refines canopy temperature measurement

Authors: Sudduth, Kenneth - Ken

Submitted to: Irrigation Today
Publication Type: Trade Journal
Publication Acceptance Date: 12/18/2019
Publication Date: 1/27/2020
Citation: Sudduth, K.A. 2020. New system refines canopy temperature measurement. Irrigation Today. 4(3):6.

Interpretive Summary:

Technical Abstract: Like other aspects of agriculture, irrigation management has entered the information age. More and more, producers are adopting sensor-based decision-making as they look to increase efficiency and cut costs. Irrigation scheduling based on plant stress, often by comparing crop canopy temperature to air temperature, is one well-researched approach. Often, the canopy temperature is obtained from an infrared thermometer (IRT) above the crop at one or more places in a field. A problem with IRTs is that they give an integrated temperature measurement of everything in their field of view. Especially early in the growing season, this may include more soil than crop, resulting in data that are not representative of the true canopy temperature. To solve this problem, our research group in Columbia, Missouri, developed a low-cost prototype sensor that could ignore the temperature of the non-crop background and provide the temperature of just the canopy. Our group, including University of Missouri and USDA-ARS researchers, developed the MSICC (Multi-band System for Imaging a Crop Canopy) using low-cost, readily available electronic and imaging components. The MSICC included two cameras, one to capture visible images and the other a long-wave infrared (LWIR) camera to obtain temperature images. An interface board with an imbedded micro-computer controlled the cameras, capturing and storing image data. The MSICC works by using the output of the visible camera to separate the crop portions of the image from the parts that are bare soil or residue. This “mask” is then used to remove the non-crop portions of the LWIR image. Finally, a calibration, accurate to 0.65 ºC (1.17 ºF), is applied to calculate the temperature of the crop portion of the LWIR image. Because the MSICC gives an image, temperature variability across the canopy can be obtained, along with the average. Field tests showed that the MSICC is able to remove shaded areas and soil from thermal images and provide temperature measurements more representative of the active part of the crop canopy. The article shows how the visible image of corn plants is used to remove the hotter bare soil between the rows and provide a temperature image of the crop. The MSICC is currently in prototype form, and more work is required before it is ready for use. Several improvements to the hardware and software of the system are needed, as are long-term field tests to evaluate its robustness and function under varying environmental conditions. If it passes these hurdles, the MSICC could provide another alternative for producers wanting to schedule irrigation based on temperature measurements of crop stress.