Kansas: Irrigation Study Uses Infrared Cameras to Improve Water Efficiency

Photo: Nick McMichen

Kansas State University researchers have tested the reliability of thermal infrared cameras in controlled, greenhouse settings and say they are now ready to take the sensors to the field to help farmers more efficiently irrigate their crops.

Ajay Sharda, an assistant professor of biological and agricultural engineering, said he’s certain that the technology can help farmers conserve water while giving their crops the water they need across the entire field.

“This will give us the ability to understand spatial (whole field) crop water needs,” Sharda said. “We will be able to more efficiently water the entire field, based on where water is needed at a given time.”

This summer, Sharda and the research group will use unmanned aerial vehicles, or drones, to fly infrared and near-infrared cameras over about five acres of corn near Rossville, Kansas. The cameras will tell them which areas are getting too much, the right amount, or not enough water.

What they’ll be measuring is canopy temperature, a measure of the electromagnetic radiation being released by the plants. Canopy temperature is thought to be a good indicator of plant stress and can provide continuous information on water status, water use and how a plant is functioning metabolically.

“We hope to capture the differences in canopy temperatures because of the level of irrigation and the type of stress the crop is experiencing,” Sharda said, adding that because they’ve proven the reliability of the cameras, “we know that we have a sensor in our hand that can pick up electromagnetic energy or radiation in terms of differences in canopy temperature.”

The work in the greenhouse was an 80-day study in which researchers controlled for several variables, including the amount of water each plant received and even the angle and altitude from which the camera took measurements.

“We wanted to understand the capabilities of these thermal infrared cameras, including how good they are and what can be captured in terms of crop canopy,” Sharda said.

The university’s research also includes work on the ground, such as sensors to measure soil moisture and a spot thermal camera to measure actual canopy temperature. They will also be tracking air temperature, humidity, solar radiation, sky temperature, and temperature reference data from panels laid in the field.

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All of the data allows researchers to build a thermogram, or a map of the canopy temperatures in the field. “From that, and including information from the environment and other sensor data, we can create Crop Water Stress index maps,” Sharda said.

Kansas State University has long been a pioneer in the art of irrigation scheduling, largely based on a measure known as evapotranspiration, a combination of water evaporation from plant leaves and the soil’s surface. ET-based irrigation scheduling, introduced by K-State researchers in the early 1980s, uses these estimates to determine the amount of water to apply and when to apply it.

Sharda’s work could help to refine where to apply it. In other words, all plants in a field may not need water at any given time or in the same quantity, so water can be directed only to those areas that are deficient.

“We are going to take data before irrigation and again after applying irrigation to determine plant stress and response to a management decision,” Sharda said. “In doing that, I have completed a feedback loop. We can say, ‘this is what it looked like, and we used that information to apply water and see if there is the expected response.’

“K-State has excellent tools for irrigation scheduling, but if we get more information on a spatial (field) scale, we can do a much better job in providing irrigation scheduling, such as how we should move our pivots, and understanding how much we can extend irrigation timing and not hurt our yields.”

It may sound complicated, but the research is intended to develop practical applications that producers or consultants will be able to easily employ, Sharda said. The technology also should increase farmers’ year-to-year understanding of water needs on their fields.

“That may be more valuable than anything else,” he said. “That’s the point where we start to learn how to use water. We have more information, now we start to figure out how much water we need, and the farmer knows how their soils and their field respond to that water. They can talk to people and say ‘guys I need this kind of a hybrid,’ or, ‘I need to do something else because these areas are my traditionally high-irrigation-need areas but they’re not giving me a lot of yield.’”

In addition to Sharda, the research team includes K-State Research and Extension irrigation specialist Danny Rogers; Pavithra Prabhakar and William Hsu from K-State’s department of computing and information science; and Guanghui Wang from the department of electrical engineering at the University of Kansas.

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