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Effect of Planting Date on Days to Maturity in Corn (5/31/18)

Good planting progress occurred this past week and most of the corn and small grain acres are now planted.

Effect of Planting Date on Days to Maturity in Corn

Good planting progress occurred this past week and most of the corn and small grain acres are now planted. Because of the late spring this year, some crops were (or will be) planted late relative to their optimum planting period. Earlier I wrote about the potential yield loss associated with delayed planting. In addition to the effect of late planting on yield, others have expressed interest in knowing the relationship between planting date and days to maturity. In both wheat and corn, there is a predictive relationship between growing degree days (GDD) and maturity. Not surprisingly, later planted small grains take fewer calendar days from planting to maturity than those planted earlier because they accumulate GDD more rapidly earlier in their growing cycle (see article by Jochum Wiersma, University of Minnesota Extension Agronomist, which follows).

The same type of phenomenon exists for corn where the number of calendar days between planting and black layer is fewer in late-planted corn compared to early-planted corn. During early vegetative develop this is easy to visualize as GDDs are minimal in early May compared to those during early June. Corn planted on May 1st, for example, will take 24 days to emerge, while corn planted on June 1st will take 15 days (using normal GDD accumulations for Fargo and assuming that 120 GDDs are needed for emergence). Unlike small grains, however, GDD accumulations start to slow during the latter part of grain filling in corn. This results in late-planted corn taking slightly more calendar days to progress from silking to black layer than early-planted corn. The amount of “catch-up” in development is therefore reduced somewhat. The net result of late-planting, however, is that later planting corn requires fewer calendar days to reach maturity than an early-planted crop. Additionally, research has shown that fewer GDDs are required for late-planted corn to reach maturity than early-planted corn. It is not clear to me why, but research has shown that a full season hybrid grown in the central Corn Belt needs 150 fewer GDDs to reach maturity when planted in early June than the same hybrid planted in early May (Nielsen et al., 2002, Agronomy Journal 94:549-558). These data are supportive of using hybrids that are slightly later than would be recommended based solely on the GDD requirements to reach maturity when planting is delayed beyond the optimum planting window.

Joel Ransom

Extension Agronomist for Cereal Crops

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