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Corn maturities for late-May planted corn

D. R. Hicks, Agronomy and Plant Genetics

A major portion (76%) of the Minnesota corn crop has been planted with the remainder delayed because of wet soil conditions and growers may wonder about the maturities of the hybrids they will be planting. Growers have made hybrid choices based on maturities for their normal planting dates. Growers should "stay the course" with their hybrid choices if they can plant by or prior to May 25. If planting does not occur by May 25, then consider maturities as given in Table 1.

There are other reasons to "stay the course" with the hybrids that growers have chosen. For the past several years, growers in the southern 2/3 of the corn growing area in Minnesota have chosen hybrids with maturities 5 to 10 less than normally considered to be "full season". The reasons for this have primarily been the excellent yields of the earlier hybrids and the opportunity for an earlier harvest period. So with the earlier hybrids, there is more calendar time during planting that these hybrids will still be "maturity adapted", i.e. they have a wider window for planting with a high probability that the grain will reach full maturity before the first killing frost.

Other reasons to "stay the course" are: Growers have chosen their hybrids because of yield potential and experience with some or all of their initial hybrids that they have chosen. Changing to "earlier" hybrids may not result in the best yielding hybrids in those maturities (assuming that growers in more northern areas have already bought the best yielding hybrids in those earlier maturities and there is little to no seed left of these best yielding hybrids). And the physical process of exchanging seed is logistically difficult to manage for seed suppliers. Some growers may ask to exchange seed and be successful, but exchanges would be difficult for all growers to do.

Table 1. Recommended corn hybrid maturities or late planting.
Planting DateRelative Maturity Units Earlier than Full Season*
May 25 - May 31 5 - 7 Relative Maturity Units
Jun 1 - 10 8 - 15 Relative Maturity Units
Jun 11 - 15 15 or more Relative Maturity Units
*For areas where 105 RM hybrids are full-season, one should plant hybrids with maturity ratings of 100 or less for grain production.

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