Field trials show benefits of carbon

CHAMPAIGN, Ill. — Four nutrient elements typically provide the foundation for crop production, but there’s a fifth one that shouldn’t be overlooked.

“The four main nutrients that come to mind are nitrogen, especially when we’re talking about corn, phosphorous, potassium and one that’s becoming more common is sulfur,” said Darby Danzl, a master’s student working with Fred Below, University of Illinois plant physiologist, at a crop nutrition field day hosted by The Mosaic Company.

The fifth element, carbon, makes up nearly 50% of a plant’s biomass and an application would provide greater nutrient uptake efficiency among other advantages.

“Typically, when you think about carbon and its relationship to a plant, you think about the plant up-taking carbon through photosynthesis which the plant then converts to above-ground and below-ground plant biomass,” Danzl said.

“At the end of the crop’s life cycle, once the plant breaks down the carbon goes into the soil. Once the carbon is in the soil it becomes organic carbon, and organic carbon is very important for soil health. That’s because organic carbon makes up a majority of organic matter.”

Organic carbon and organic matter in soil are responsible for promoting many functions in the soil that sets the foundation for a healthy, high-yielding crop.

“Organic carbon is responsible for soil structure, soil water-holding capacity, and by increasing carbon levels you can increase nutrient availability and use efficiency,” Danzl said.

“Typically, farmers already applied their nutrients and they’re relying on the carbon that’s already in the soil from previously degraded biomass and rely on that interaction.”

Field Study

Field trials were conducted at the U of I in 2020 that focused on applying carbon with the fertility that’s already being applied.

Humic acid was used as the carbon source in the trials. There were four treatments in the study — unfertilized control; humic acid; monoammonium phosphate and muriate of potassium; and MAP, MOP and humic acid.

The unfertilized field yielded 255 bushels per acre. The yield gained an additional 3 bushels per acre where humic acid was applied, and the yield went up to 260 bushels per acre where MAP and MOP were applied.

When humic acid was applied along with MAP and MOP, there was a 21 bushel increase over the unfertilized field.

“This is what we as scientists like to call a synergistic relationship. We think by applying the carbon with the traditional fertilization it’s increasing their efficiency. This is what I call a win, win, win situation,” Danzl said.

“It’s a win because you’re increasing the nutrient use efficiency of the fertilizer you’re already applying, and you’re promoting higher yield on a yield that is already high. Both are wins because you’re improving your soil function and soil structure and you’re sequestering carbon.

“If you have higher yields, you have more carbon, and by applying these amendments directly to the soil, you’re increasing the carbon, as well.”