URBANA, Ill. — A March 12 webinar forum offered by the University of Illinois Extension examined methods to maximize the value of field residue, or convert “trash” into “treasure.” Though residue can present issues at planting time and is often regarded as “trash” by farmers, U of I researchers including Dr. Connor Sible and Crop Physiology Lab masters student Ava Isaacs have been studying the nutritional value residue can offer to a subsequent crop and its ability to maintain healthy soils year after year. 

“There has been a consumer shift away from chemical-based systems to sustainable or regenerative agriculture-based systems, and with that residue is a really big topic,” said Isaacs, who will complete her masters later this year. She added that residue is enjoying a higher level of discussion lately because of increases due to wider use of cover crops and enhanced yields. 

“As grain yield goes up, so does our stover biomass. For every bushel of corn increase, there are 44 more pounds of residue. If you are increasing your yield by 20 bushels an acre, that’s 880 pounds of residue that you’re adding back into the field. At 180 bushels per acre, you’re looking at around four tons per acre of residue in your field,” Isaacs explained, adding that while some farmers see residue as trash, savvy ones regard it as treasure.

“Too much residue can be a problem at planting, but there are a lot of nutrients tied up in corn residue. For nitrogen, for every one ton of residue there is 20 pounds of N. So if we are looking at a 230 bushel per acre corn crop there is around 5.5 tons of residue per acre, around 108 pounds of N per acre and 21 pounds of phosphorus. For potassium, it’s 122 pounds per acre,” she said. 

“This (corn residue) is treasure, but as when you often find treasure, there is usually a lock on it. You have to find the key to unlock the treasure, and residue is the same way. I like to think of it as a big machine, and to unlock the value of your residue there are three speeds or gears, and the first one is to Convert,” said Isaacs. 

She explained how the Conversion gear involves residue degradation, specifically the encouragement of such. The second gear involves the Capture of the nutrient value of the residue degradation, and the third gear Creates plant growth and higher yields.

Adding fall fertility to residue can encourage microbes to accelerate degradation, according to Isaacs. Microbes prefer a C-N (carbon-nitrogen) ratio of 24-1, with anything above that ratio shown to induce N immobilization. If there is not enough N within residues microbes will pull it from the soil, creating deficiency issues. 

Studies conducted by the U of I over multiple years have confirmed that additional fertility- specifically Ammonium sulfate (AMS) — enhances degradation and improves residue. Studies have shown that mechanical slicing of the residue from tillage will also help facilitate degradation and improve residue. The result has been higher corn yields in studies conducted by the Crop Physiology Lab team. 

“Regardless of the system whether it’s standard or chopped residue, with the addition of AMS we are seeing a yield increase, especially in no-till where we are dealing with more corn residue,” Isaacs said. 

A third method of enhancing decomposition involves the use of biologicals, which the U of I team is currently studying more closely. “There is a big boom in the market of biologicals, which can be split into two groups: beneficial microbes and biostimulants. We have focused on the living beneficial microbes and how we can add on these biologicals with levels of fertility or other levels of management,” she added. 

The team’s studies continue to focus on all three methods of increasing the nutritional value of crop residue, according to Sible, who is in his tenth year working with Dr. Fred Below in the U of I Crop Physiology Department, first as a student and now as a faculty member. “We’re looking at the options we have in agronomic management solutions for residue, and it’s really the mechanical, the chemical and the biological. How we then integrate that into useful systems that can benefit is where we will transition now,” he said. 

The entire March 9 webinar, “Maximize the Value of Your Residue,” will be archived at https://farmdoc.illinois.edu/webinars.