Hitting the Hot Spots

UGA teams with Israeli researchers to improve irrigation efficiency in cotton

Variable rate irrigation (VRI) is a form of precision agriculture that allows farmers to apply different amounts of water to different areas of a field. When combined with soil moisture sensors, VRI greatly increases the efficiency of irrigation. Now three University of Georgia scientists are collaborating with Israeli experts in thermal imaging to make VRI even more efficient when irrigating cotton.

UGA Tifton campus crop and soil scientists George Vellidis, John Snider and Vasileios Liakos are working with Yafit Cohen and other Israeli researchers to combine the technologies.

“We have all this expertise on dynamic VRI and they have all this expertise on thermal imaging, so we joined forces to see if we can develop a method for mapping dynamic management zones. We want to be able to map soil-drying patterns in fields as they change from day to day,” said Vellidis, an expert in precision agriculture and variable rate irrigation. “Not only are we telling the pivots to apply different amounts of water in different management zones, but the shapes of those zones are changing every day. We want to map drying patterns with thermal images and use the soil moisture sensors to tell us how much to apply. The whole idea is to improve the efficiency of the system.”

As plants become water limited, they close the pores on the surface of their leaves and their temperature goes up, said Snider, a cotton physiologist who has researched stress levels in cotton. A leaf’s temperature is directly related to how much water it can move from its roots to the atmosphere. If there’s not enough water in the soil, the plant can’t transport water to the leaves and the leaves shut down, resulting in the rise in temperature.

Cohen, a research scientist with the Agricultural Research Organization in Israel’s Ministry of Agriculture and Rural Development, and her colleagues use thermal imaging that can detect canopy temperature differences within 1 degree Celsius.

Thermal imaging is valuable because it focuses on the canopy temperature of the plant, while soil moisture sensors examine just the soil.

“Using thermal imaging, you can quantify how stressed different parts of the field are. You can capture the entire field and determine if one part of the field needs to be irrigated compared to another,” Snider said. “To do this, you’ve got to be an expert in image analysis. You have to take these images, put them together and interpret the temperature data, and convert that to different levels of water stress throughout the field.”

This research project used tools to examine a cotton field including drone-based infrared and multispectral cameras and a tower-based thermal infrared camera that remotely views canopy temperatures. The tower-based camera is mounted on a 50-foot mast and can survey the whole field.

UGA-Tifton graduate Stefano Gobbo (MS – Crop and Soil Sciences, ‘18) tested the technology used to map canopy temperature while studying with Snider.

Lorena Lacerda, a doctoral student in Vellidis’s lab, spent three weeks in Israel with Liakos learning to use the thermal imaging software and to process images.

While thermal imaging is key to understanding when the plants need water, it can’t tell the researchers how much water to apply to the soil. Using this technology in concert with soil moisture sensor networks makes the process “super efficient,” Vellidis said.

“Think of it this way — we know fields contain areas that aren’t farmed. It might be a drainage ditch or a wetland area or a badly eroded area. It’s not where you’re growing anything, so why put water there? The ability to turn off the pivot’s sprinklers over those areas — that’s variable rate irrigation,” Snider said. “But being able to respond to crop needs in the farmed areas when you need to — that’s where we’re wanting to take this further. We want to use our strengths to maximize that efficiency.”

The three-year project, which began in 2017, is funded by the U.S.-Israel Binational Agricultural Research and Development program.

By Clint Thompson

Student holding drone in field
Photo by George Vellidis