Focus on Agriculture: Managing corn stover a growing issue for farmers

Posted: Sep. 22, 2011 9:31 am Updated: Nov. 28, 2014 2:17 pm

It's time to determine what to do with corn stover.

"Corn stover has become more of a management concern over the years as new hybrids produce stronger stalks, relatively larger amounts of biomass, more corn-on-corn acres are planted and less tillage is done," said Fabian Fernandez, University of Illinois Extension soil and plant fertility specialist.

Stronger stalks are a desirable trait to help with standability of the crop, he said, but the drawback is those materials are more difficult to break down in time for the following growing season. Stalks, along with other crop residues, can interfere with planting in the spring.

A practice that is increasingly being promoted is applying nitrogen, typically urea-ammonium nitrate (UAN) or ammonium sulfate (AMS), to increase microbial activity and induce residue decomposition.

"Microbial decomposition of corn stover is typically slow because the material has a high C:N ratio," Fernandez said. "The basic concept behind application of N to the residue is that by applying N, it is possible to reduce the C:N ratio and allow microbes to act on, or start eating, the material quicker."

While this concept makes sense, research conducted at the University of Wisconsin found applying nitrogen in the fall to aid the breakdown of corn stover was not justified because it did not contribute to residue breakdown and resulted in nitrogen loss. "Nitrogen loss is not only undesirable due to environmental degradation, but it reduces profitability," Fernandez said.


Effective weed management

Take advantage of the elevated view from the combine cab to survey and assess the effectiveness of weed management programs.

"A field free of weeds during harvest is very desirable and represents an outcome that will require increased management as weeds continue to adapt to modern crop production practices," University of Illinois Extension weed specialist Aaron Hager said.

The spread of waterhemp and horseweed poses concerns.

"Glyphosate resistance in Illinois waterhemp and horseweed populations is known to occur, and we suspect this will become increasingly common in future growing seasons," he said. "Additionally, resistance to five different herbicide site-of-action families has been documented to occur in Illinois waterhemp populations. In all instances except one, these resistance traits can be transferred by movement of both pollen and seed."

Herbicide-resistant populations generally do not infest an entire field over the course of a single growing season. Rather these populations usually begin as a small number of plants that survive to produce seed.

The next season the herbicide-resistant population may exist as a patch of weeds encompassing a small area within the field. Rogueing these plants from the field before they produce viable pollen and seed can help slow the spread of the herbicide-resistant population within the field and reduce the movement of the resistance trait to other fields.

"Female waterhemp plants have the potential to produce in excess of one million seeds per plant, although that number is usually much smaller when the waterhemp plants have grown under competitive conditions," he said. "If you notice a few surviving female waterhemp plants in a field, it might be a good investment of time to remove those plants before they enter the combine. Combines can spread weed seed across a field and transport seed from one field to another."

Compiled by Herald-Whig Staff Writer Deborah Gertz Husar.



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