Corn production in the Mid-South has increased in recent years. As with other major crops, profit from growing corn depends on making correct production decisions.

The Mid-South states conduct corn variety trials to provide data to assist producers with hybrid selection. Because of the high cost of hybrid corn seed, choosing the highest-yielding hybrid with the desired agronomic and genetic traits is probably the most important production decision a grower will make.

One aspect of hybrid selection that may be overlooked in the decision-making process is the relative maturity or growing season length of individual hybrids. Corn is usually classified into early-, medium-, and full-season categories based on a relative maturity classification that is commonly expressed in days-to-maturity.

The days-to-maturity designation is a misnomer, since the length of time for a hybrid to reach maturity varies with latitude and planting date, among other things.

However, this system is reasonably accurate in expressing the relative growing season length and the maturity of a hybrid in relation to other hybrids. It is widely used by seed companies across the United States, and hybrids have this designation in their descriptions.

Data from irrigated corn variety trials in Missouri, Tennessee, Arkansas, Mississippi, and Louisiana were summarized to assess the effect of relative maturity (used here to replace days-to-maturity) on yield. Yields from studies conducted in 2005 and 2006 at the locations shown in the accompanying table were used.

For the purpose of comparison, relative maturity is divided into three levels. These designations correspond to what is commonly referred to as the aforementioned early- (110-113 days), medium- (114-116 days), and full-season (117-120 days) categories.

Within each maturity class and test location of each year, yields of the top five hybrids were averaged to obtain the yields shown in the table. The number of hybrids from each of the three maturity classes that yielded in the top 15 at each test location in each year are also shown.

At every location from the north Delta (Portageville, Mo.) to the south Delta (Yazoo City, Miss.) in both years, the trend was for the five best short-season hybrids to have the lowest yield.

There was no consistent trend in differences between average yields of medium- and full-season hybrids. However, in all but two cases, there were more medium-season than full-season hybrids among the top 15 yielding hybrids.

This assessment of recent variety trial results using available hybrids (no experimentals) indicates that corn producers throughout the lower Mississippi River Valley should be planting medium- and full-season hybrids when irrigation is used during the growing season.

Since cost of seed corn is not related to maturity classification, choosing a high-yielding hybrid from within these two maturity classes should result in greater profit.

Data from only irrigated trials were used to remove drought stress as a factor in this assessment.