The economics of corn grain production make June planting in Wisconsin marginal due to lower yield and high grain moisture. In Wisconsin, yield of corn planted in early June decrease at the rate of 3% per day delay. In most years the latest economical planting date for corn grain production in northern Wisconsin is June 1, while for southern Wisconsin corn should not be planted for grain production after June 10.

Maturity switch dates for corn in southern Wisconsin are May 20 and June 1 where on each date hybrid maturity should be 5 to 10 RM units shorter-season than the "full-season" hybrid used for the field. The decision depends upon drying cost and grain price. When grain prices are low and drying costs are high, switch dates are earlier. For northern Wisconsin there is only one maturity switch date on May 20. Yield is not different between full- and shorter-season hybrids when planted in June, but shorter-season hybrids should be used to better manage risk from fall frost.

Corn can still be planted in June, but in most years it should be intended for high moisture grain or silage use. In general silage yield decreases 31 to 41% as planting date is delayed from the optimum date to June 20. The economic trade-offs are difficult to establish for late planted corn silage. Milk per acre is more affected than silage yield due to the low grain content of the silage. Most of the silage yield reduction is due to grain yield reduction thereby decreasing the energy content of the silage. In most years, planting date and maturity switches for corn silage use should be the same or slightly later than those for grain use. Although there may be more flexibility in years where grain prices are low when it may be possible to add grain to corn silage for later planting dates thereby raising quality. The economics of this management decision must be carefully considered.

Deciding when to quit planting corn is not an easy decision. In some years we can have a late fall frost and later planting dates can do fairly well. A number of factors should be considered when deciding whether or not corn should be planted in June.

Corn production costs (Drying costs): Shorter-season hybrids reduce the risk of immature and wet grain in the fall. But, ultra-short- and short-season corn hybrids must have adequate yield potential to recover production costs.
Corn price: Higher corn prices make planting later into June with shorter-season hybrids more attractive.
Other uses: Corn used for other purposes such as high moisture grain or corn silage can be planted later into June than corn harvested for grain. High moisture grain and silage allow the use of longer season hybrids with greater yield potential.
Other cropping alternatives: Compare the relative yield potential of an alternative crop for a given date with that of late planted corn. For example, corn yield potential declines at a faster rate than the yield potential of soybeans. Other crops to consider include sunflowers, buckwheat, and sorghum-sudan grass.
Environment: First fall frost date and fall drying conditions influence your decision. Years that are longer and warmer thGeneral guidelines for June corn planting in south and south central Wisconsin are:

Corn for grain can be planted until about June 1-10;
Corn grown for high moisture corn and silage uses can be planted until about June 10-20;
After June 20, consider switching to a different crop.

Less flexibility for corn planting dates in June is observed in northern Wisconsin.