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College of Food, Agricultural, and Environmental Sciences


Careful Corn Planting Can Reduce Yield Losses

March 22, 2007

COLUMBUS, Ohio -- Proper planting practices are the first step to overcoming yield limitations the environment can put on a corn crop.

Peter Thomison, an Ohio State University Extension agronomist, said that impact of compaction, especially when drought occurs, can cost growers 5 percent or more of their corn yields, depending on the production situation, location, hybrid planted and soil type. Mistakes made during planting operations that can lead to uneven stands, for example, can just compound the problem.

"Mistakes made during the planting operation are usually irreversible, and can put a ceiling on the crop's yield potential before the plants have even emerged," said Thomison, who holds a partial research appointment with the Ohio Agricultural Research and Development Center.

The following are some recommended practices to help get the corn crop off to a good start:

• Perform tillage operations only when necessary and under the proper soil conditions. "Avoid working wet soil, and reduce secondary tillage passes," said Thomison. "Shallow compaction created by excessive secondary tillage can reduce crop yields." He added that deep tillage should only be used when a compacted area has been identified and soil is relatively dry.

• Complete planting by mid-May. "The record corn yields of recent years owe much to timely planting and good seedbed conditions. If soil conditions are dry, begin planting before the optimum date," said Thomison. "The recommended time for planting corn in northern Ohio is April 15 to May 10 and in southern Ohio, April 10 to May 10." Thomison recommends avoiding early planting on poorly drained soils or those prone to ponding. "Yield reductions resulting from "mudding the seed in" may be much greater than those resulting from a slight planting delay."

• Adjust seeding depth according to soil conditions to avoid poor root development, shoot uptake of soil-applied herbicides, and uneven plant emergence. "Plant between 1.5 inches to 2 inches deep to provide for frost protection and adequate root development. In April, when the soil is usually moist and evaporation rate is low, seed should be planted no deeper than 1.5 inches," said Thomison. "When soils are warm and dry, corn may be seeded more deeply up to 2 inches on non-crusting soils."

• Adjust seeding rates on a field-by-field basis. "Adjust planting rates by using the yield potential of a site as a major criterion for determining the appropriate plant population," said Thomison. "Most research suggests that planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates." On productive soils, with long term average yields of 160 bushels per acre or more, final stands of 30,000 plants per acre or more may be required to maximize yields. On soils that average about 150 bushels per acre, a final stand of 28,000 plants per acre may be needed to optimize yields. On soils that average 120 bushels per acre or less, final stands of 20,000 to 22,000 plants per acre are adequate for optimal yields.

• Calculate appropriate seeding rates. "The number of plants per acre at harvest is always less than the number of seeds planted. Planting date, tillage practices, pest problems, chemical injury, planter performance, and seed quality can affect final corn populations obtained in the field," said Thomison. "To compensate for these losses, a corn grower needs to plant more seed than the desired population at harvest. When early planting is likely to create stressful conditions for corn during emergence, consider seeding rates 10 percent to 15 percent higher than the desired harvest population." To learn more about calculating appropriate seeding rates, go to OSU Extension's C.O.R.N. (Crop Observation and Recommendation Network) newsletter at

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Candace Pollock
Peter Thomison