Choose hybrids that have produced consistently high yields across a number of locations and/or years. The Ohio Corn Performance Tests (OCPT) indicate that hybrids of similar maturity vary in yield potential by as much as 40 bushels per acre or more. Choosing a hybrid because it possesses a particular trait, such as big ears, many kernel rows, deep kernels, prolificacy or upright leaves, does not ensure high yields; instead, look for stability in performance across environments.
Most of the hybrids marketed and planted in Ohio contain transgenic traits for herbicide and insect resistance. Planting herbicide-resistant hybrids allows growers to use herbicide formulations also used on soybeans. Hybrids with glyphosate and/or glufosinate ammonium resistance offer weed management options that generally involve fewer applications and use of more environmentally benign chemicals. Insect resistant hybrids contain a gene from bacteria that produces the insecticide known as Bt. Planting Bt corn hybrids may eliminate the need for soil insecticide treatments (rootworm) and post-emergent insecticide applications (corn borer), which are less effective and potentially harmful to nontarget beneficial insects. See the section on Insect Control in this chapter for more on the use of Bt resistance to minimize crop losses.
A major concern of growers is whether the yield potential of hybrids with fewer transgenic traits or no transgenic traits is less than that of stacked trait hybrids with multiple genes for above- and below-ground insect resistance. One explanation for this concern is that some seed companies are no longer introducing non-transgenic versions of certain hybrids or are releasing non-trans- genic versions some years after the original hybrid has been introduced. So, when a new high yielding hybrid is introduced, it’s often only available with stacked traits. As a consequence, some growers believe that in order to optimize yields with the newest genetics it’s necessary to plant stacked trait corn hybrids with transgenic traits for above- and below-ground insect resistance. An assessment of corn hybrids in the OCPT without transgenic traits (non-GMO); with transgenic herbicide resistance only; with transgenic traits for above-ground insect resistance only; and with transgenic traits for above- and below-ground insect resistance indicated that non-transgenic hybrids are available that yield competitively with many transgenic corn hybrids in the absence of corn borer and rootworm pressure. Similarly, yields of hybrids with transgenic traits for above-ground insect resistance only were comparable to yields of hybrids with transgenic traits for above- and below-ground insect resistance. As to whether different insect and herbicide traits and combinations thereof affect hybrid performance (in the absence of insect pressure), OCPT data suggested that no set of traits performed consistently much better or much worse than other sets of traits and the numbers of traits was not highly correlated with yield performance among these sets.
Several major seed companies have recently introduced corn hybrids that specifically target enhanced drought tolerance. To date, these drought tolerant hybrids from Du-Pont Pioneer (Aqua Max) and Syngenta (Agrisure Artesian) contain native traits and those from Monsanto (Drought- Gard) a transgenic trait. In field studies conducted by Ohio State from 2012–2014, drought-tolerant hybrids from DuPont Pioneer and Syngenta were compared to conventional hybrids of similar relative maturity. Results suggested that in moderate- to lower-yielding environments in Ohio (below 185 bushels per acre average yield), the drought-tolerant hybrids can produce greater yields than their conventional counterparts under the same management conditions, but the yield may not be greater when conventional hybrids yield more than 185 bushels per acre. Drought-tolerant hybrids may offer a yield advantage in production environments at greater risk to water deficit with moderate- to low-yield potential.
Some investigators have reported that corn hybrids with different genetic backgrounds vary in their response to plant population and nitrogen fertilizer, and many seed corn companies characterize hybrids based on their response to plant population and nitrogen fertilizer. However, most university research indicates that differential response among hybrids for nitrogen and population is often inconsistent, strongly influenced by environmental conditions, and not a practical consideration when making nitrogen and seeding rate recommendations. Nitrogen and plant population response for different hybrids has also been found to vary by site and weather conditions.
Review the results of state, company and county performance trials before choosing hybrids. 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 over a wide range of locations and climatic conditions. When using university performance trials results, two years of data from several locations is usually adequate; test summaries for three or more years may exclude new hybrids with better performance potential. Moreover, most hybrids are not evaluated in the OCPT beyond two years.
On-farm strip tests are not reliable in hybrid selection because they cannot predict hybrid performance across a range of environmental conditions. However, on-farm hybrid tests can be useful in evaluating various traits, such as lodging, greensnap, drydown, harvestability (ease of shelling, ear retention, etc.), disease resistance and staygreen.
The Ohio State University conducts corn performance tests across Ohio. Test results are published each year in a bulletin titled Ohio Corn Performance Test, Agronomy Dept. Series 215, and is also available online at: oardc.ohio-state.edu/corntrials/. The bulletin summarizes hybrid tests conducted each year at 10 Ohio locations and includes yield information from the previous two years. The bulletin includes data on yields, grain moisture and standability of hybrids.