Anyone who's talked with a seed salesman over the past 20 years has heard these terms: flex-ear, girthy or fixed ear, racehorse hybrid, workhorse hybrid. Yet Dave Nanda, a plant breeder with four decades of experience, contends that these terms don't adequately reflect the ability of today's corn hybrids to compensate when placed in different environments.
Nanda, Indianapolis, says that the labels, used by companies and salesmen as gospel, are actually limited in scope. Under the right environmental conditions, both types of ears may add rows of kernels. Under poor conditions when corn plants are making key decisions, the same hybrids may drop a couple rows of kernels.
Row number is highly linked to genetics. However, environment also influences it. This includes everything from how close the plant is to another corn plant or weed, soil fertility levels, and whether it's too hot, too dry, too warm, too cool or 'just right.'
"Corn plants have one goal," Nnada says. "That is to produce as many viable progeny as possible. So if conditions are good as the season unfolds, the corn plant sets up to produce as many kernels as it can. If conditions change and go south once ear row number is set, for example, it will compensate perhaps by dropping back on the number of kernels per row. Or if conditions are good, it will increase the number of kernels per row per ear."
So-called girthy-ear hybrids can also add more kernels and fill to the tip if conditions are favorable, Nanda says. Flex-ear hybrids are the ones noted in the industry for having that ability. Both can drop kernels if conditions aren't favorable. Kernels at the tip or near the tip may abort if the plant thinks it won't be able to develop those kernels properly. Instead, it will concentrate on filling as many viable kernels as it can.
Nanda has actually broken types of ears into five classes, not two. And while he believes his descriptions come closer to explaining how corn plants can compensate under various conditions, they are still labels which don't fit in every case.
Compensation continues until the black layer forms. If late conditions are favorable, plants can add more starch and increase test weight. If the crop runs into dry conditions, or is negatively affected in some other way, test weight may be lower instead of higher. Once the black layer forms, no more starch can enter or leave the kernel. The compensation process is over, Nanda says.
Nanda believes it's important for farmers to understand how each hybrid they grow can compensate. And while there may be genetic differences, it's important to understand that all hybrids can adjust in its' own way to environmental conditions, either good or bad.