August 10, 2022

Cover crop support tool updated

Site-specific answers

CHAMPAIGN, Ill. — Further updates have been made to a first-of-its-kind web tool to help Illinois farmers manage cover crops.

The free Cover Crop Decision Support Tool was developed by the University of Illinois’ National Center for Supercomputing Applications, with a collaborative team that included agronomists, climatologists and biological engineers.

The goal of the Cover Crop Decision Support Tool — — is to help provide site-specific answers to decisions not only surrounding the adoption, but also real-time management of cover crops.

Funding for the program is provided by the Illinois Nutrient Research and Education Council and the Walton Family Foundation. Initial seed funding also was provided by the McKnight Foundation and U of I.

Details of the funding and updates were provided in the Dec. 22 Illinois Nutrient Loss Reduction podcast hosted by Todd Gleason, U of I media communications specialist.

Participants were Jonathan Coppess, assistant professor, U of I Agricultural & Consumer Economics; Illinois State Climatologist Trent Ford; Rabin Bhattarai, associate professor, U of I Agricultural & Biological Engineering; and Shalamar Armstrong, associate professor, Purdue University Department of Agronomy.

The updates included providing improved weather forecasts, especially for the spring season, and improved estimates of nitrogen loss reduction.

“The idea comes out of the Nutrient Loss Reduction Strategy and the need for farmers to reduce the loss of nitrogen in particular in Illinois,” Coppess said.

“We know cover crops are arguably the most effective in-field practice to cut nutrient loss because you’re growing it in a fallow season. It’s going to absorb or scavenge that extra nitrogen; it’s going to hold it in the crop biomass, so it’s not going to be leaching into the tile to the waterways and all the way down to that dead zone in the Gulf of Mexico.

“We understand cover crops have these benefits, but for the farmer there’s added cost, added management needs, added risk putting a crop in what was normally fallow and then you have to deal with that crop particularly in the spring planting window.

“So, we started working with Rabin and NCSA to try to design away to provide a best estimate modeled outcomes and what’s going on in a field if you put a cereal rye cover crop in.”

Timely Forecasts

“When Jonathan presented the tool and the problem, he said they want farmers to have the right information in front of them when they’re making decisions and of course a lot of those decisions, whether it be termination or how much nitrogen they’re storing, they need to know how weather conditions are going to affect that. Not today or tomorrow, but two, three, four weeks from now,” Ford said.

The Cover Crop Decision Support Tool has integrated an ensemble of medium-range weather forecasts using data produced by the National Oceanic and Atmospheric Administration’s Subseasonal Experiment.

The tool uses SubX forecasts for improved cover crop decision outlooks. Each week, the latest 30-day forecast will be retrieved and used when running the Decision Support System for Agrotechnology Transfer crop model.

“The National Weather Service puts out a seven-day forecast and that’s really not enough lead time to make decisions. We pulled in the National Oceanic and Atmospheric Administration’s forecast from their sub-seasonal experiment. This is started from a research experiment and has grown to operations to try to improve sub-seasonal prediction,” Ford continued.

“Historically predicting one-week time scales has been fairly easy, it’s been improved by quite a bit, but the two- to four-week time scales are not. NOAA has this project to improve those forecasts.

“We bring those in from a multitude of different climate and weather forecast models. There are forecasts of temperature and precipitation and they’re operational so they’re updated at least once a week so we can update them as well as update the tool once a week or even sooner with those two- to four-out weeks of weather conditions.”


Daily inputs into the program’s model include temperature, rain totals, the amount of water that ran on the soil surface in a field and the amount of water going into the soil profile.

“We compute a layer by layer calculation like how does the soil moisture change as water moves into the soil horizon, how does the nitrogen concentration in the soil change as water moves to the horizon and what can happen to the water that can be sucked by the plant root and how that moisture content can drop in a couple of days as the plant draws water from the soil profile,” Bhattarai said.

“We’re putting that together in the system to see, for example, if a farmer grows a cover crop in this field for his location, for weather conditions, for soil condition, how does that cover crop make a difference in terms of water dynamics, in terms of how much tile water flow can be reduced by the cover crop, and how much nitrate loss can be reduced from his field by planting this cover crop.”

The model used is an open source.

“This has been built and worked on by a lot of scientists over time and one of the things that I think we would argue that’s somewhat unique about this project is we’re sort of in the quintessential extension mindset. We’re translating this into something useable so that we are tapping into that research capability,” Coppess added.

The tool simulates cover crop growth and soil nitrogen dynamics for the field. It visualizes the outputs of the model simulation in a dashboard, and the primary data visualized is the total biomass for the cover crops in the field, as well as the carbon-to-nitrogen ratio.

Combined, this provides the farmer with a better understanding of the cover crop dynamics, helping to manage termination and overall management such as planting and fertilizer.

“For example, you may have 2,000 pounds of biomass per acre out there. You may have to figure out how to do that. Everything from the equipment needs, the timing needs, to how you think about getting into that field and planting into that cover crop,” Coppess said.

“You’re termination timing is going to be key. We can see this at the end of our dashboard in that April/May timeframe, as we pull in more growing degree days over time, that cover crop is going to takeoff. The difference in terminating April 15 versus March 15 could be pretty significant what you’re doing with the equipment you need, what you’re going to plant, trying to figure out what the nitrogen outcome is. You may need starter because that plant has taken up a lot of nitrogen into the biomass so you’re not going to get it.”

Field Trial Data

Armstrong has been conducting cover crop field trials on a farm near Lexington since 2014 and the data has been plugged into the Cover Crop Decision Support Tool.

The trials document cover crop growth, biomass, nitrogen content within the biomass, carbon content within the biomass and quantify the impact of the presence and performance of cover crops to decrease nitrate loss in tile drainage.

“We’re also measuring the cash crop yield. That’s also a critical component that helps understand the hydrology and the loss of nutrients. That’s also a component of data from the field study that’s underpinning the tool,” Armstrong said.

“The tool helps farmers visualize and conceptualize cover crop growth on their field. You may have a farmer who’s thinking about adopting cover crops this year. What the tool does is to say before you actually put it in the ground, let’s model this before your very eyes, so you can play with the idea of having cover crops on your farm.

“The farmer can select the field where they want to grow cover crops and they are then allowed to give some input data on what their management is, whether they’re growing corn or soybeans, the nitrogen they are applying, when they will apply nitrogen, when they would like to plant the corn and when they would like to terminate the cover crop.

“Then that farmer would run the tool and the tool would generate what the biomass would be over time and it will give an output of a graph of above ground cereal rye biomass accumulation over time. At the same time, it’s also giving the carbon dioxide/nitrogen ratio of that biomass in an output graph.

“Also in the output is a key component of the percent of nutrient loss reduction. In other words, what’s the percent reduction in nitrate loss from the tile drainage because of the presence of the cover crop?”

Tom Doran

Tom Doran

Field Editor