Corn Hybrid Selection

The MSU Corn for Grain Hybrid Trials provide grain yield, hybrid maturity, lodging, grain moisture, rainfall, crop history, and other data relevant to rating performance. Results presented in this format may be difficult to analyze, since grain yield differences between hybrids often are subtle or variable. Variability in hybrid testing can be expected due to the complexity of interacting factors that influence grain yield, coupled with the number of entries grown in the tests. Hybrid performances should be evaluated from averages of several locations and/or years of data to obtain an accurate assessment of performance under a variety of environmental conditions.

Give careful attention to yield relative to the test average. It is highly recommended to yield-test several promising hybrids alongside established standard hybrids on your farm. This lets you evaluate your own soil types and cropping systems.

Hybrid maturity is a major consideration in hybrid selection. Maturity is most commonly expressed as a number of days needed to reach physiological maturity. This method can be rather arbitrary due to variability of environmental influence on physiological development. Many seed companies are also designating maturity based upon number of the Growing Degree Units (GDU).

Growing Degree Units are calculated by subtracting a base temperature of 50 °F from an average of the maximum and minimum daily air temperatures. Daily maximum temperatures above 86 °F are counted as 86 °F, and temperatures below 50 °F are counted as 50 °F because temperatures exceeding these base temperatures do not contribute more or less, respectively, to growth. Hybrids currently marketed normally range from 110 to 125 days, or 2,700 to 3,100 GDU's.

Late-maturing hybrids generally have more yield potential than do the early maturing hybrids. However, early maturing hybrids often yield favorably to late-maturing hybrids, especially under stressed conditions. Corn grain development is most susceptible to stress during silking and pollination. Early maturing hybrids reach their susceptible silking period a few days earlier in the season.

Corn developing earlier is more likely to experience lower temperatures, longer days, more stored soil moisture, and greater likelihood of rainfall. Planting early generally results in higher yields for these same reasons. Accordingly, advantages of early maturing hybrids are nullified by late planting.

Numerous other plant characteristics contributing to stand establishment, plant health, and harvest ability influence grain yield and hybrid selection. Some of these characteristics include early vigor, stay-green ability, drought tolerance, insect and disease tolerance, and stalk and root strength. In the past, late-maturing hybrids often had advantages for these characteristics over early maturing hybrids, because breeding and marketing efforts were highly concentrated on this maturity group for the Midsouth. However, selection efforts concentrating on early maturing hybrids have narrowed this advantage considerably. Seed company product guides, state hybrid trials, and agribusiness and Extension personnel can provide guidelines for selections based on these criteria.

Because of the complexity of factors that may influence grain yield, it is highly recommended to select several adapted hybrids to plant on your acreage. Planting several hybrids that differ in maturity or other plant characteristics lessens the risk of a particular environmental stress, disease, or any uncontrollable circumstance causing crop disaster to the entire acreage.

By Dr. Erick J. Larson, Extension Agronomist

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Information Sheet 1547
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. RONALD A. BROWN, Director

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