Margaret A Smith, PhD | Agronomist
Jake Hansen | Corn and Soybean Agronomist

Corn planting has been clipping along at a nice pace in the central Corn Belt, but has been delayed in Minnesota, Wisconsin, and the Northeast, due to a cold, late, spring and, in some areas, excessive rainfall. Long-term trends illustrate that corn yield potential is reduced when planting into late May. But, if your fields were underwater, there’s not much you can do, except make the most of the growing season that’s left!

As planting is delayed, corn will develop and mature with fewer growing degree days (GDDS) than when planted early, so full-season hybrids can be planted later and still mature in good time. But, when planting after May 21-25, to increase your chances of best economic yield (combined grain yield and dry down), we suggest shortening your corn relative maturities by 5 to 7 days. Guidelines for late planting date adjustments vary a bit by individual state recommendations (see table, below).

Organic growers planting into this May 21-25 planting window have likely already selected shorter-maturity hybrids.

For both conventional and organic farms, if corn planting is delayed beyond June 1-5, reduce maturities an additional 5-7 days or switch to soybeans. For June planting for silage, switch to very early corn maturities, or forage sorghum or sorghum x sudangrass.

Adjustments to Corn Relative Maturities (CRM) when planting is delayed.

Table 1: Corn Late Planting Guidelines



Adjusted CRM

University of Minnesota May 21-28, May 29-June 4 5-7 days earlier, 8-15 days earlier
University of Wisconsin May 21 7 days earlier
South Dakota State University May 25, June 5 5 days earlier, 10 days earlier
Iowa State University June 1 Not defined (we suggest 5-7 days earlier)
Purdue University Last week of May Not defined

Check your state’s specific late corn planting recommendations with the links provided, below.