Creating A Simple System to Pinpoint Irrigation Using Crop Temperatures

Kendall DeJonge’s mission is to take plants’ temperatures.

But the crops, like corn, that he is working with don’t have to open up and say, “ahh.” Instead, DeJonge employs an infrared radiometric thermometer (IRT). This is a simple point-and-detect tool that any farmer could own. The USDA Agriculture Research Service (ARS) engineer, who works out of Colorado, is developing a simple way that farmers can use IRT to pinpoint when a crop needs to be irrigated.

DeJonge is basing his work on research that confirms thirsty plants get hot. So a simple method of taking crop canopy temperatures could be a boon to farmers. And, DeJonge points out, IRTs could be placed on posts in fields, center pivot irrigation systems, or even a drone to gather temperature readings on crops. Scientists can interpret the IRT data by using one of several indices, including the commonly used crop water stress index (CWSI). Developed by ARS scientists in the early 1980s, the CWSI requires knowing air temperatures and humidity levels to calculate a “vapor pressure deficit,” in addition to knowing the canopy temperature. Although accurate, CWSI is fairly technical to use.

DeJonge and his team of researchers have developed two new indices which are simpler to employ than CWSI. These formulations include the degrees above non-stressed (DANS) index and the degrees above critical temperature (DACT) index. DeJonge’s team found that DANS and DACT were just as effective as CWSI at determining water stress. Not only is either calculation far simpler to use but also crop canopy temperatures need to be taken just once a day to be accurate.

DeJonge is now working on refining the calculations to establish water needs of specific crops under different scenarios. With his crop water-coefficient data, farmers could use handheld or drone-mounted IRTs to calculate water needs over extensive areas.

For more information, you can contact DeJonge at kendall.dejonge@ars.usda.gov.