Hard Driving Rains May Cause Some Soil Crusting Problems

May 20, 1999 6(9):55-56

Joe Lauer, Corn Agronomist

Relatively good field conditions were seen early for corn planting. Planting progress throughout Wisconsin is ahead of the 5-year average. The soil in many fields worked up very fine. Recent hard driving rains has led to soil crusting problems at a time when the crop is emerging.

Poor emergence due to soil crusting conditions might tempt some farmers to replant. Unless stands are under 15,000 plants/A replanting probably won't pay. For example, a field in southern WI planted May 1 with a stand 30,000 plants/A would produce 100% of the expected yield for any year. If the stand was reduced to 18,000 plants/A, yield would be 85% of a stand at 30,000 plants/A. Replanting to a full stand by May 20 would produce 87% of the expected yield and not be economical. However, if stand was reduced to 12,000 plants/A, yield would be 69% of a stand at 30,000 plants/A. Replanting to a full stand of 30,000 plant/A might be warranted if the decision could be made by May 20. It would not be economical if the decision was delayed until June 1.

For a complete discussion on replanting decisions in Wisconsin see the UWEX Bulletin A3353 (http://cf.uwex.edu/ces/pubs/pdf/a3353.pdf). The decision depends primarily on:

  1. Original planting date and desired plant population
  2. Health condition of emerged plants
  3. Evenness of stand
  4. Comparison of the yield potential of a reduced stand to that of a replanted stand (Table 1.)
  5. Replanting costs
  6. Risk

There is no guarantee that replanting will produce a full stand. If the factors that reduced the initial stand (i.e. diseases, insects, herbicide injury) are still present or could possibly occur again (i.e. soil crusting), the replanted corn will likely also suffer.

Table 1. Expected corn yield for various planting dates and harvest populations in Wisconsin.
  Original planting date
(full-season hybrid)
Replanting date
(shorter-season hybrid)
Harvest population May 1 May 10 May 20 June 1
Plants / A % of expected yield % of expected yield
Southern WI        
30,000 100 94 87 72
24,000 95 91 83 68
18,000 85 80 74 61
12,000 69 67 60 50
Northern WI        
30,000 97 94 79 63
24,000 91 88 75 59
18,000 83 80 68 54
12,000 72 70 59 47

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