INFORMATION REQUIRED TO MAKE A CORN REPLANTING DECISION

The following information must be gathered while you are in the field inspecting the damage. Additional information, such as original planting date and possible replant cost, will be required to determine if replanting is justified.

After-Damage Plant Population

Surviving plants should be counted in at least 3 different 1/1000th acre lengths of row in 4 different sites in the damaged field, for a total of 12 plant counts. See page 213 of this guide to determine what length of row equals 1/1000th acre for the row width of the field. See chart to determine effects of reduced plant population and delayed planting dates on grain yield.

After-Damage Stand Uniformity

When making plant counts, note skips or gaps visible in the row. Was average length more or less than 3 feet? Gaps of 4 to 6 feet can cut yields about 5%.

Growth Stage of Corn

What was the growth stage of the corn when the damage occurred? Use the growth stage definitions used in estimating losses due to defoliation.

After-Damage Plant Defoliation

If leaves have been damaged or destroyed, what was the average percent loss in leaf area for the total crop? See pictures to determine estimated percent leaf loss. See chart to determine yield loss.

Should You Patch-In a Poor Stand?

  • If you replant within 2 weeks of planting the original, patching-in may be a viable option. Yields will be similar to those from a uniform-emerging replanted stand, if you can get relatively uniform plant spacing within the row between the old and new plants. Within 2 weeks of planting, it is often too early to determine what the final stand will be (and whether patching will be needed).

  • If you replant within 3 weeks after the initial planting, yield potential is about 10% greater if you tear up the field and start over with an even emerging stand rather than just patch-in the original stand. Balance this possible yield increase against the additional cost of tillage, seed, and dryer fuel.

    • Should you replant stands with uneven emergence?

  • If the delay in emergence is less than 2 weeks, replanting will have a minimal effect on yields, regardless of the pattern of unevenness.

  • If one half or more of the plants in the stand emerge 3 weeks late or later, then replanting may increase yields by up to 10%. To decide whether to replant in this situation, estimate both the expected economic return of the increased yield compared to your replanting costs and the risk of emergence problems with the replanted stand.

    • Should late emerging plants be protected during row cultivation?

  • If the delayed plants emerge only 1 to 2 weeks late, use shields and avoid burying the late- emergers during cultivation.

  • Protect plants emerging 3 weeks late if one half or more of the plants in the stand are late emergers.

  • If less than 1/4 of the stand emerges 3 weeks late or later, will probably not pay to encourage their survival. Yields will be about the same whether or not these delayed plants are buried during cultivation.

    • Source: National Corn Handbook Chapter 36, "Effects of Uneven Seedling Emergence in Corn"

    ASSESSING FLOODING AND PONDING DAMAGE TO CORN The extent to which flooding injures corn is determined by several factors including: (1) plant stage of development when flooding occurs, (2) duration of flooding and (3) air/soil temperatures. Prior to the V6 stage (6 visible leaf collars) or when the growing point is at or below the soil surface, corn can generally survive only 2 to 4 days of flooded conditions. The oxygen supply in the soil is depleted after about 48 hours in a flooded soil. Without oxygen, the plant cannot perform critical life sustaining functions; e.g. nutrient and water uptake is impaired, root growth is inhibited, etc. If temperatures are warm during flooding (greater than 77° F) plants may not survive 24-hours. Cooler temperatures prolong survival.

    To confirm plant survival, check the color of the growing point. It should be white to cream colored, while a darkening and/or softening usually precedes plant death. Also look for new leaf growth 3 to 5 days after water drains from the field. Sometimes the growing point is killed by bacterial infections during and after flooding, but plant growth continues in the form of non-productive tillers (suckers).

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    Corn, Soybean, Wheat, and Alfalfa Field GuideBulletin 827