Residue Management in a Field of Lodged Corn

• Nearly every year, adverse weather and crop conditions result in lodged corn in some fields. Lodging may be caused by a windstorm, stalk rot or other disease, rootworm activity, or some combination.
• The damage varies considerably depending on the severity of lodging. Lodging not only impacts the yield potential of a corn crop, but also creates a residue management problem, especially in fields where lodged corn goes unharvested.
• Increasing the rate of residue breakdown can be aided by practices that enhance soil health and soil microorganism populations.

What can I do to manage heavy corn residue in fields with severe lodging?

Tillage incorporates residue into the soil where soil microbes help increase decomposition rates. Less residue on the soil surface helps increase soil warming and facilitate planting operations. Most primary tillage implements, including chisel plows, mulch rippers, disk rippers, and off set gang discs are designed to incorporate some, but not all, of the crop residue on the soil surface. In addition, the depth and speed of tillage, and type of shovel or point selected will determine the amount of soil moved and residue incorporated. Vertical tillage implements employ narrowly-spaced ripple coulters that help to size stalk and root ball residue prior to primary tillage. Strip tillage combines the soil warming and drying benefits of tillage with the soil conservation benefits of no-till.

Chopping or shredding stalks in the fall with a flail-type or rotary blade chopper can help manage residue. Stalk chopping flattens the residue profile and distributes stalk residue between the rows, which can impact the ability of planting next year's crop between last year's rows. Flattened residue is more prone to "matting" on the soil surface, and can result in cool, wet soil in the spring.

Another alternative to tilling the soil is to process the residue with the combine corn head at harvest. Decomposition rates will be substantially increased when the leaves and stalks have been crimped, chopped or crushed at the corn head.

Finally, cattle producers may consider grazing the field or baling some of the corn stalks for feed or bedding.

What environmental conditions help facilitate residue breakdown?

Crop residue is composed of lignin, cellulose, hemicellulose, and nutrients. Microorganisms break down these compounds, and the decomposition rate is largely affected by moisture and temperature. Warm, moist weather in conjunction with smaller pieces of residue that maximizes contact between residue and the soil helps increase the rate of residue decomposition. Dry soils and low temperatures inhibit residue breakdown.

If the corn crop was damaged prior to maturity, then the residue may break down at a faster rate than undamaged residue remaining after harvest. The amount of carbon (C) and nitrogen (N) in vegetative components and grain would be different than at harvest. With the lower C:N ratios, the earlier stage vegetative and grain material should be more easily decomposable.

Can fall-applied nitrogen help with residue breakdown?

Nitrogen deficiency symptoms can occur during immobilization; however, research has not consistently shown a benefit to fall N applications intended to assist in residue decomposition.¹ Timing, cooler temperatures, and/or dry weather might play a role in the effectiveness of fall N applications. In most of the corn growing region, microbial decomposition of residue is limited by low temperature. Therefore, from economic and environmental perspectives, N application has little effect in achieving the intended results of facilitating residue decomposition.

What are other management strategies that can be used to help manage residue?

Increasing soil microorganism populations can help increase residue decomposition. Cover crops provide additional moisture, energy, carbon, and nitrogen to help sustain activity of a wide range of soil microorganisms. For fields that remain unharvested and tillage is used to size residue, seeding a cover crop after the tillage operation can provide soil cover and protection. For fields harvested for silage or baled, seeding the cover crop immediately after harvest provides the best establishment window.

Crop rotation cycles that include legume crops with lower C:N ratios return N back into soil faster and gives residue with higher C:N ratios (such as corn) more time to decompose. Successfully planting cover crops, such as cereal rye, in fields that are not harvested will greatly depend on reducing the size of the corn residue and increasing seed to soil contact. This can be accomplished through discing, vertical tillage or stalk shredding.

Sources:

¹ Al-Kaisi, M. 2019. Corn Residue Breakdown as Affected by Tillage and N Application. Iowa State University. https://crops.extension.iastate.edu/cropnews/2019/11/corn-residue-breakdown-affected-tillage-and-n-application.

Staton, M. 2011. Corn residue management begins in the fall. Michigan State University Extension. https://www.canr.msu.edu/news/corn_residue_management_begins_in_the_fall.

Al-Kaisi, M. 2014. Myths and facts about residue breakdown. Iowa State University. Integrated Crop Management News. https://crops.extension.iastate.edu/cropnews/2014/04/myths-and-facts-about-residue-breakdown.

Al-Kaisi, M.M., Hanna, M., and Petersen, T.S. 2009. Residue management and cultural practices. Iowa State University Extension, PM 1901a. https://www.extension.iastate.edu/.

Sawyer, J. August 28, 2020. Biological breakdown of wind destroyed corn. Integrated Crop Management. Iowa State University Extension. Biological Breakdown of Wind Destroyed Corn | Integrated Crop Management.

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