K-State research is testing ET-based irrigation decisions

At Kansas State University (K-State), researchers are testing different technologies to help producers make irrigation decisions as water availability becomes less predictable. 

One current project is led by Gaurav Jha, assistant professor of precision agriculture at K-State, and a team at the Kansas Water Institute. They are testing the free OpenET tool, created by a network of scientists, water managers, technologists and nonprofits, including NASA. This open-access platform measures evapotranspiration (ET) at the field scale under real farm conditions on operating farms. Their goal is to determine how satellite-based ET data can translate into practical irrigation scheduling. 

“The radar systems retrofitted in a pivot provide high-resolution information about soil moisture distribution across the field, while OpenET gives us the crop water use signal from above,” Jha said. “When you bring those two together, you start to close the loop between what the crop is using and what the soil is supplying.”  

This integration shifts irrigation scheduling decisions away from fixed schedules toward field-level water-use information and needs. In fields where variable-rate irrigation is available, growers can use that same information to adjust application across management zones, he explained.  

“Across different systems, the interaction is slightly different,” he said. “In all cases, the role of OpenET is to provide a consistent, field-scale measure of water demand that connects directly to irrigation decisions.” 

Current study findings 

The ongoing study, conducted in partnership with the Kansas Water Office, is showing that irrigation is no longer just about maximizing yield.  

“The margin for error [for irrigation decisions] is shrinking,” he said.  

One test site is the Flickner Innovation Farm in central Kansas, a 1,000-acre irrigated corn, wheat and soybean operation where the team is combining OpenET with advanced irrigation technologies, including radar-based soil moisture systems and precision irrigation platforms. 

He highlighted four of the biggest research takeaways thus far: 

1. Fields are more variable than they are typically managed. Water use, soil moisture depletion and crop response can look very different from one zone to another, even under one center pivot. Uniform irrigation often means some areas are overwatered while others are already stressed.  
2. Timing matters more than volume. In several of the team’s on-farm trials, they are seeing that well-timed irrigation, even with slightly less total water, can maintain yield compared to higher but poorly timed applications. That is a shift from thinking that more water is safer to understanding that the right water at the right time is more effective.  
3. No single data stream is enough on its own. Satellite-based water use, soil moisture sensors and crop stress indicators each tell part of the story. When they are integrated, the decisions become much clearer. 

“In many cases, the difference between efficient and inefficient irrigation is not how much water is applied, but how well it matches crop demand in space and time,” he said. “Today, irrigation is about managing a finite resource under uncertainty, where today’s decisions directly affect how long that system remains viable.” 

4 strategies for use in any field 

While declining water availability in the Ogallala Aquifer in the southern High Plains of Kansas inspired the research, Jha noted that producers in any state can use these irrigation management decision tips to improve watering efficiency:  

• Change how you look at your field. Start by asking a simple question: Is my field behaving uniformly, or am I managing it that way out of convenience? Pull up your yield maps, think about soil differences, topography and how water moves across the field.  

• Build one layer at a time. That could be tracking irrigation amounts more carefully, using a soil moisture probe in a representative zone, or looking at evapotranspiration trends to understand how quickly the crop is using water. You do not need 10 tools.  

• Pay close attention to irrigation timing. Instead of focusing only on how much water to apply, focus on when the crop is approaching stress. Even small timing adjustments can improve efficiency without changing your entire system. 

• Treat your field as zones, not as a single unit. Even if you do not have variable-rate irrigation, understanding which parts of the field dry down faster or respond differently will change how you think about irrigation scheduling. 

“The impact is not just saving water. It is changing how decisions are made by our farming community,” he said. “Irrigation becomes less about habit and more about timing and response. In a region like Central Great Plains, where every inch of water matters, that shift is everything.”