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Virginia Cooperative Extension - Knowledge for the CommonWealth

Achieving Uniform Corn Stands

Crop and Soil Environmental News, April 2006
Wade Thomason, Extension Grains Specialist, Dept. of Crop & Soil Environmental Sciences, Virginia Tech

Uneven plant spacing and emergence may reduce yield potential in corn. Corn should be planted as uniformly as possible within the row to ensure maximum yields. Uneven emergence generally has greater impact on grain yield than uneven plant spacing. Uneven emergence results in competition from larger, early-emerging plants that decreases the yield from smaller, later-emerging plants. Emergence delays of 10 days or more result in growth stage differences of two leaves or more. When two plants differ by two leaves or more in growth stage, the younger, smaller plant is more likely to be barren or produce a small ear. Delays of less than 10 days usually do not result in significant yield loss due to competition.

Uneven emergence and plant spacing can be due to unfavorable environmental conditions at or immediately after planting, but often these problems result from worn or poorly adjusted planters. Timely maintenance and following planter operating instructions can avoid many problems and ensure uniform stands.

Some tips for improving seed spacing uniformity and emergence.

  1. Check finger pickup planters for wear on the back plate and brush.
  2. Check for wear on double-disc openers and seed tubes.
  3. Check for worn chains, stiff chain links, and improper tire pressure.
  4. Clear seed drop tubes of any obstructions.
  5. Check the alignment of coulters and disc openers.
  6. Verify settings on the planter transmission.
  7. Use the correct plates to match the seed grade planted.
  8. Match the air pressure to the weight of the seed being planted.
  9. Make planter adjustments and follow lubricant recommendations when using seed-applied insecticides. Unless these precautions are followed, the extra chemical coating on the seed may adversely affect the seeding rate - vacuum planters may underseed and finger pickup planters may overseed. To improve planter accuracy, talc or graphite should be used according to the planter manufacturer's recommendations. With vacuum planters, it will probably be necessary to raise the vacuum level.
  10. Keep it slow. Maintain planting speed within the range specified in the planter's operators manual.

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