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:
- Original planting date and desired plant population
- Health condition of emerged plants
- Evenness of stand
- Comparison of the yield potential of a reduced stand to that of a replanted stand
(Table 1.)
- Replanting costs
- 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.
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Table 1. Expected corn yield for various planting dates and harvest populations in
Wisconsin.
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Original planting date
(full-season hybrid)
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Replanting date
(shorter-season hybrid)
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Harvest population
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May 1
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May 10
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May 20
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June 1
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Plants / A
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% of expected yield
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% of expected yield
|
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Southern WI
|
|
|
|
|
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30,000
|
100
|
94
|
87
|
72
|
|
24,000
|
95
|
91
|
83
|
68
|
|
18,000
|
85
|
80
|
74
|
61
|
|
12,000
|
69
|
67
|
60
|
50
|
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Northern WI
|
|
|
|
|
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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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