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Replant or Not? Consider these factors.

Agronomy Bulletin 1 ─ Northern Corn Belt Replanting Decisions

Situation

If your cornfields have been damaged by heavy rain, hail, pests or poor emergence, you may consider replanting.

Factors to Consider

  • Yield potential of existing stand
  • Yield potential of replanted corn
  • Replanting date
  • Replanting costs
  • Availability of earlier-maturing hybrids
  • Weed control implications
  • Grain moisture content at harvest
  • Crop insurance adjustments
Table 1. Grain Yield Loss Based on Plant Population for Corn Planted Prior to May 1

Action Plan

  1. Calculate yield loss from less-than-optimum plant population. To estimate yield loss due to stand reduction, first determine the plant population of the existing stand. Then refer to Table 1 to determine the yield loss based on the existing plant population. In the example highlighted in the chart, assuming an optimum plant population of 30,000, a grower can expect a yield loss of 6 percent when plants per acre drop to 26,000.
  2. Factor in additional yield loss for nonuniform stands. Uniformly spaced plants produce more yield than unevenly spaced plants. Large gaps of 2 feet or more in the stand can reduce grain yield by about 5 percent in populations of 14,000 to 28,000 plants per acre. If plants are uneven, add another 5 percent to the estimated yield loss due to stand reduction.
  3. Estimate yield loss due to later replanting date. Using Table 2, determine the expected yield loss for a later-than-optimum planting date. For example, with a replant date of May 30, a grower could expect a yield reduction of 17 percent. Optimum planting dates vary by location.
  4. Compare yield potential to determine if replanting is worthwhile. Using the examples cited, a grower could expect a yield loss of 6 percent due to stand reduction and a loss of 17 percent due to delayed replanting. Therefore, the yield potential of the replanted corn does not outweigh the yield potential of the existing stand and the grower would probably choose not to replant.
  5. Other considerations. If corn is severely damaged, another option to consider is switching to a later-season crop. If you do choose to replant, a local crop consultant or agronomist can help select hybrids with shorter relative maturities appropriate for your area.
Table 2. Grain Yield Loss Based on Corn Planting Dates

Summary

When faced with a replant situation, analyze all factors to determine whether the yield potential of the replanted corn will offset the cost of replanting. For more information, contact your local Mycogen Seeds commercial agronomist or trusted agronomic adviser.

Resources

Published on Sunday, March 02, 2014