Managing the Effects of Crop Residue in Continuous Corn
 Corn is considered as high residue crop and managing crop residue in a continuous corn cropping system
can be challenging.
 Crop residue if not managed properly, can decrease emergence and vigor, harbor disease pathogens, and
immobilize nitrogen that would make it unavailable to the corn crop.
 Several practices discussed in this article will help growers manage residue when growing continuous corn.
Negative Effects of Excessive Crop Residue
Excessive crop residue at planting can interfere with good seed
to soil contact, leading to poor emergence and vigor.6 Diseases
such as gray leaf spot, Northern corn leaf blight, diplodia, and
anthracnose overwinter in corn residue. If most of the residue
decomposition is occurring during the growing season, the
nitrogen (N) required for decomposition can limit the N available
for corn growth (Figure 1). All these agronomic risks can lead to
potential yield loss if crop residue is not properly managed.
A
C
Crop residues that have higher carbon to nitrogen (C/N) ratios
generally take more time to decay and result in higher amounts
of N being required by soil microbes to lower C/N ratio of many
residues.3 When the microbes break down residues that are
high in carbon, such as corn, they can outcompete growing
corn for available N in order to maintain their own preferred C/N
ratio of 10:1.7 This immobilization of available N can result in
nitrogen deficiency symptoms until the majority of the
decomposition is complete. Mineralization occurs as the
microbes die and release the N back into the soil (Figure 2).
Some of the conditions that favor decomposition of residue
include time, warm moist weather, smaller pieces of residue,
and maximizing the contact between residue and the soil.
Figure 2. The interaction between available nitrogen and microbial activity that aids
in decay of crop residue. (Adapted from Modern Corn and Soybean Production.)
B
D
Figure 1. If corn residue (A) is not properly managed, the
risk of poor emergence and vigor (B), nitrogen deficiency
symptoms (C), and diseases such as gray leaf spot (D), are
likely to increase.
Basics of Residue Composition
In terms of N cycle, the process of breaking down of
residue uses immobilization and mineralization which
both involve soil microbes (Figure 2). Immobilization is
when N is consumed by soil microbes. Mineralization is
the release of N that generally happens upon the death of the
soil microbes. The soil microbes feed on the carbon (C) in crop
residues and require N to do so. Soil microbes generally try to
maintain a carbon to nitrogen (C/N) ratio of approximately 10:1.
C/N ratios of crop residues vary greatly. Alfalfa, soybean, and
other legumes generally have lower C/N ratios near 15:1 and
mineralization often occurs quickly.
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Practices that Assist in Managing/Decomposing
Excess Residue
Harvest continuous corn fields first to help maximize the time
and available warmer weather to aid microbial activity.
Combine heads can be set to cut
about a foot (or more) above the
Managing the Effects of Crop Residue in Continuous Corn
ground.1 Additionally, some heads are available that chop the
residue as it is fed through the head.
Chopping stalks into smaller pieces can aid in residue break
down, but having a mat of residue may make planting more
difficult.
“Vertical” tillage is a form of conservational tillage that aids in
sizing of residue but limits the disturbance of the soil. Vertical
tillage tools cut the residue into small pieces for even
distribution and better contact with soil.9
Aggressive tillage can help maximize contact of residue and
soil. Doing tillage, whether aggressive or “vertical”, as soon as
possible after harvest can help take advantage of warmer
weather and increased microbial activity. Often tillage can be
done in the fall and the spring. Chisel plowing can leave
approximately 50% to 80% of the residue on the soil surface.2
Fall chiseling followed by spring cultivation can leave between
18% to 41% residue on the soil surface.
Fall N applications to aid in decomposition are greatly
debated. The concept is that applying N in the fall can stimulate
soil microbes and hasten the degradation of corn residue.5
However, research has not consistently shown a benefit to fall
N applications intended to assist in decomposition. Some
believe this lack of response to be real, due to N not being the
limiting factor for decomposition at the time it was applied in the
fall. Other potential limiting factors that might play a larger role
than N might be cooler temperatures and or dry weather which
can impede microbial activity. There are others who believe the
lack of response indicated in research is not reflective of what
occurs in a field setting. They contend that the environmental
conditions and variability that make N research difficult masked
the benefits of fall N applications intended to break down
residue. This debate is not likely to be settled in the near future.
If considering this type of fall N application, consider leaving a
check strip for comparison purposes.
Higher N rates might be an option since much of the N
normally applied may be immobilized by microbes for residue
degradation during much of the growing season. The amount
of additional N needed would depend on the other conditions
that influence microbial degradation. For example, a corn crop
that is following a late harvest, cold winter, and early planting
season may benefit from more N compared to a corn crop that
is following an early harvest, warm winter, and normal planting
season.
Planters equipped with row cleaners should be utilized to move
residue and enhance seed to soil contact.4 Row cleaners allow
quicker soil warm up within the planting zone.
Uniformity of the Residue Unevenly distributed crop residue
across the soil surface hinders seedbed preparation and create
poor seed-to-soil contact.8 This can lead to poor stand
establishment and decreased yield potential. Spreaders can be
used to evenly distribute residue behind the combine.
In fields where continuous corn is practiced, surface residue
can harbor some disease pathogens. Burying the residue is an
option to control potential disease development.
Product Selection
Choose products with high ratings for emergence, seedling
vigor, and root and stalk strength.6 Continuous corn can also
increase some insect, weed, and disease problems but these
issues can be managed with a strong seed/trait selection and
herbicide and fungicide programs. Genuity® SmartStax® RIB
Complete® corn blend contains trait protection with multiple
modes of action for above and below ground insects. Using
residual herbicides in combination with a Roundup Ready®
system can improve weed management.
Sources:
1
Al-Kaisi, M. 2007. Tillage challenges in managing continuous corn. Iowa State University
Extension. Integrated Crop Management. http://www.ipm.iastate.edu (verified 8/05/13);
2
Moncrief, J. 2002. Tips for profitable crop residue management systems. University of
Minnesota. www.extension.umn.edu (verified 8/05/13); 3 Mannering, J. and D. Griffith. Value
of crop rotation under various tillage systems. Purdue University Extension. AY-230. http://
www.extension.purdue.edu (verified 8/05/13); 4 Randall, G. et al. 1996. Tillage best
management practices for continuous corn in the Minnesota River Basin. University of
Minnesota Extension FO-06672. http://www.extension.umn.edu (verified 8/05/13).
5
Nafziger, E. 2007. Notes heading Into harvest 2007. University of Illinois Extension. The
Bulletin. No. 22. Article 6. http://bulletin.ipm.illinois.edu (verified 8/05/13); 6 Nielson, R.L. et.
al. 2007. Mitigate the downside risks of corn following corn. Purdue University Extension.
Corny News Network. http://www.agry.purdue.edu (verified 8/05/13); 7 Hoeft, R.G. et. al.
2000. Modern corn and soybean production. MCSP Publications. Champaign, Illinois. Pages
121-131;8 Residue management and cultural practices. PM 1901a. Iowa State University
Extension. http://www.extension.iastate.edu (verified 8/05/13); 9 Harrigan, T. 2011. Manage
high yielding corn with vertical tillage. Michigan State University Extension.
http://msue.anr.msu.edu (verified 8/07/13).
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