Is your corn mature and ready for harvest, or did it die from thirst and exposure like a skeleton in the desert?  The latter could be the case in many parts of the Cornbelt as the calendar rolls into a new marketing year.  Planting was delayed, but the corn “speed-grew” and now it may be ready for harvest several weeks before you were planning.

As several hundred thousand farmers comb over the exhibits and watch field demonstrations at the Farm Progress Show, host farmers readily acknowledge a speedy season cut yields from their demonstration fields.  Although the short season corn from Wisconsin was planted to be harvestable by the end of August, it also had the benefit of a Southern Illinois summer and maturity was advanced significantly.

Purdue agronomist Bob Neilsen says delayed planting often increases the risk that the grain will not mature before a killing freeze in the fall.  But he says under “normal” planting dates and growing conditions the calendar time from grain fill to maturity is similar across a wide expanse of the Cornbelt.  Many farmers may be plagued with the question of whether there is enough of the growing season left to help the corn reach maturity.

Purdue’s Neilsen says corn hybrids mature with fewer accumulated heat units when planted late compared with “normal” planting dates.  He says simultaneous research in IN and OH indicated there was not a consistent north/south relationship. 

But is maturity more than just formation of the black layer in the corn kernel?  Purdue’s Neilsen says it occurs within the range of 25% to 35% moisture and will vary year to year within one hybrid.  He says the traditional method of rating the maturity of corn is based on comparisons of hybrids near the point of maturity, when grain moisture loss is about 0.5 percentage points per day.

He says many folks have used the word “days” to the rating value, but it is important to recognize that it does not refer to actual calendar time from planting to maturity.  The other common method is based on the amount of accumulated heat during the growing season.  He says, “Since this method depends on actual measurement of thermal time, there is no need to compare hybrids in order to assign maturity rating values. In other words, the maturity rating for an individual hybrid stands on its own.”

Neilsen says the relationship between those two formulas is close, but not exact because one is based on physiological maturity and the other on harvest maturity.  He says neither method is perfect because of the influence of climatic conditions and plant stress on the grain maturation process.  And he adds that differences from one seed company to the next often result in the frustration of a farmer in trying to compare maturity values between different hybrids.

Some corn has matured and other corn has died from lack of moisture and the ability to photosynthesize.  Corn that matures has reached certain physiological states based on a variety of yardsticks, including accumulation of heat units, and the grain maturation process. 

Source: the FarmGate blog