Crop rotation is the key to maximizing yields while reducing potential problems with insect and diseases. However, some Ohio growers are willing to accept the risks of continuous corn production in the hopes of capturing more profit from higher corn prices.

Peter Thomison, an Ohio State University Extension agronomist, is encouraging growers to follow key management practices to help reduce the risks under continuous corn production.

“Many agronomists do not recommend continuous corn. Corn grown following soybeans typically yields about 10 percent more than continuous corn,” said Thomison, who also holds a partial research appointment with the Ohio Agricultural Research and Development Center. “Additionally, growers face many challenges with corn following corn, and they need to be aware of the issues involved with the production practice.”

The biggest issue under continuous corn production is the large amount of residue that is generated. That residue can result in a variety of planting and harvesting problems, including:

• Greater levels of disease inoculum. Continuous corn increases the frequency and severity of disease problems.
• Cooler, wetter soils during and after planting, which result in delayed germination and emergence, slower vegetative growth, prolonged exposure to diseases and insects, and compaction during harvest.
• Interference with planter row units. The presence of residue from previous corn crops may cause uneven seedling depths and poor seed to soil contact.
• Decreased efficacy of soil-applied herbicides.
• Increased stand establishment problems due to slow warming and drying of soils, especially those poorly drained.
• Greater potential for nitrogen losses.

“The risk and magnitude of yield drag and other problems associated with continuous corn is greatest with no-till,” said Thomison. Other problems include a greater risk to western corn rootworm and longer harvest season due to time and capacity demands on machinery, drying facilities, transportation and storage.

“The longer corn sits in the field, the greater the risks to lodging, stalk rots and other diseases,” said Thomison.

For growers who intend to plant corn following corn or switch part of their soybean crop to corn production, several management practices can be followed that may reduce the risks and minimize potential yield losses.

Such practices include:

• Planting corn on the most fertile, well-drained soils to reduce stress and maximize yield potential. “Avoid droughty soils, as well as poorly drained soil conditions,” said Thomison.
• Developing strategies for dealing with increased crop residues. Use stalk chopper and knife rolls on combine heads; spread residue uniformly during harvest; consider strip tillage and avoid no-till where practical; avoid no-till planting on top of old rows; and use row cleaners and seed firmers.
• Managing corn diseases by selecting hybrids with good disease resistance, emergence, and seedling vigor. “Burying crop residue reduces disease pressure, but may be of limited value if neighboring corn fields are no-till,” said Thomison.
• Reducing insect risks by planting Bt rootworm hybrids, or using seed/soil insecticides. Scout fields for cutworm and army worm damage.
• Adjusting nitrogen rates. “Optimum nitrogen rates for corn after corn are generally higher than those for corn after soybean, and range from 30 to 50 pounds of nitrogen per acre,” said Thomison.
• Following standard weed management recommendations. * Scouting fields during harvest to detect stalk lodging and stalk rot. Prioritize those fields with problems for early harvest.

  “The decision to switch to continuous corn should be made carefully. Continuous corn production requires a higher level of management to achieve high yields,” said Thomison. “Although short term economics may favor corn after corn, each operation is different, and understanding the risks associated with corn after corn is the first step toward managing the practice wisely and economically.”

  For more information on managing continuous corn, log on to the Ohio State Extension Agronomic Crops Team Web site.

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