More Crops, Much More Residue

WITH MOST CORN BELT no-tillers growing only corn and soybeans, many of the major benefits of crop rotations are being overlooked. Even so, a recent University of Illinois study on the impact crop rotations have on soil quality may have raised more questions due to the favorable results found with continuous corn.

Graduate assistants Mollie Adams and Stacy Zuber recently evaluated the impact of rotations on soil bulk density, organic matter and water stability at five Illinois locations. While the results were mixed, corn and wheat residues definitely boost soil organic quality.

“We want the decomposition process to occur more slowly and this happens with both corn and wheat residue,” Zuber says.

Both corn and wheat residues attach a considerable amount of carbon to each particle of nitrogen (N). But as the soil breakdown process takes place, soil microbes need more N to free the carbon.

In these studies, a rotation of corn, soybeans and wheat improved soil quality the most. Interestingly enough, the heavy residues found with continuous corn also performed well.

“Although rotations affect the soil, there’s nothing consistent,” Adams says. “Soil is a constantly evolving thing, and there are a lot of forces acting upon it. Assessing soil quality is really complicated.”

Weather Concerns.

Much of the land in Illinois this year was inundated with excessive rainfall during the prime growth period. Water infiltration is important in such a year, since drowned-out areas are common.

“With heavy rainfall, we want to make…