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.

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