During the past 40-50 years, there has been continuous improvement in the genetics of corn hybrids, which has contributed to increases in grain yield potential ranging from 0.7% to 2.6%/year. Growers must introduce new hybrids to their acreage on a regular basis to stay competitive, says Thomison, crop science expert.
“Growers should choose hybrids best suited to their farm operation,” he says. “Corn acreage, previous crop, soil type, tillage practices, desired harvest moisture and pest problems determine needs for such traits as drydown, insect and disease resistance, early plant vigor and plant height.”
Think about the end use of corn, he says. Will corn be used for grain or silage? Will it be sold directly to the elevator or used on the farm? Are premiums available at nearby elevators or from end users for identity-preserved specialty corns such as food grade or non-biotech corn? Capacity to harvest, dry and store grain should also be considered.
Thomison recommends five steps to follow in choosing hybrids that are best suited to various production systems.
First, select hybrids with maturity ratings appropriate for the geographic area or circumstances. Corn for grain should reach physiological maturity or black layer one to two weeks before the first killing frost in the fall.
“To determine differences in hybrid maturity, use days-to-maturity and growing degree day ratings along with harvest grain moisture data from performance trials,” Thomison says. Moisture differences among hybrids should also be taken into account, as grain drying represents a major portion of the energy required for corn production, he notes.
It may be preferable to select short to mid season hybrids than full season hybrids for grain, especially if planting is delayed until late May, he says. This year’s Ohio Corn Performance Test results indicate the average yields of entries in the early maturity test were similar to those in the late maturity test; however, the average grain moisture of hybrids in the early test was 1.5-3.5 percentage points lower than those in the full season test.
Second, choose hybrids that have produced consistently high yields across many locations. Tests this year indicate that hybrids of similar maturity varied in yield potential by as much as 60 bu./acre depending on the site.
Thomison warns that choosing a hybrid simply because it’s a triple-stack, quad-stack or possesses appealing cosmetic traits, like big flex ears, will not ensure high yields. Instead producers should look for yield consistency across environments, he says. Hybrids will perform differently, based on region, soils and environmental conditions.
“Our tests this year revealed that stacked trait hybrids not only produced the highest grain yields, but also the lowest,” Thomison says. Several non-transgenic hybrids suitable for non-biotech grain production produced yields that were not significantly different from the highest yielding triple or quad stack entries, he points out. When planting fields where corn rootworm and European corn borer are likely to be problems, Bt traits offer outstanding protection and may mitigate the impact of other stressors.
Third, plant hybrids with good standability to minimize stalk lodging. This is particularly important in areas where stalk rot is a perennial problem, or where field drying is anticipated. In 2008, severe lodging was present in many western Ohio corn fields, due in large part to the high winds associated with Hurricane Ike. In addition, severe water stress in July and August in parts of Ohio may have predisposed the crop to stalk rot. Major differences in lodging were evident among this year’s hybrid entries in with percent plant lodging ranging from less than 5% to more than 90%.
If a grower has his own drying facilities and is prepared to harvest at relatively high moisture levels (greater than 25%), then standability and fast drydown rates may not be critical as selection criteria.
Traits associated with improved hybrid standability include resistance to stalk rot and leaf blight, genetic stalk strength, short plant height and ear placement, as wells as high staygreen potential. Staygreen is a hybrid's potential to stay healthy late into the growing season, after reaching maturity. Thomison cautions not to confuse it with late maturing.
Fourth, select hybrids with resistance and/or tolerance to stalk rot, foliar diseases and ear rot. For the information on the most common disease problems of Ohio corn, visit http://www.oardc.ohio-state.edu/ohiofieldcropdisease/ . In recent years, several diseases have adversely affected the corn crop, including northern corn leaf blight, Stewart’s bacterial leaf blight and diplodia ear rot. Growers should obtain information from their seed dealer on hybrid reactions to specific diseases that have caused problems or that have occurred locally, Thomison says.
Fifth, never purchase a hybrid without consulting performance data. Results of state, company and county hybrid replicated performance trials should be reviewed before purchasing hybrids, he says. Because weather conditions are unpredictable, the most reliable way to select superior hybrids is to consider performance during the last year and the previous year across a wide a range of locations and climatic conditions.
To assess a hybrid’s yield in 2008 averaged across multiple Ohio test sites look at the “Combined regional summary of hybrid performance” tables. These tables and other results for trials are available at http://agcrops.osu.edu/~perf/ . Corn growers farming along Ohio borders with neighboring states should check results of the Purdue, Kentucky, Michigan State, Pennsylvania and West Virginia corn test results. The University Crop Testing Alliance Web site, http://www.agry.purdue.edu/pcpp/UCTA/index.html , provides links to corn hybrid test results from universities across the Corn Belt.