Corn hybrids: How they developed, why it matters

By Cindy Snyder, Ag Weekly correspondent
Friday, August 31, 2007 6:19 PM CDT

Rick Speicher, with Croplan Genetics, explains how different genetic families influence ear size and root development in today's corn silage hybrids during a field day held in mid-August. Photo by Cindy Snyder/AG WEEKLY

JEROME, Idaho — Anyone who’s ever been to a family reunion has seen first hand how genetics influence families. Corn plants are no different, but growers don’t often think about genetic families when selecting hybrids.

“Every genetic family has different thresholds for plant population, soil type, stress,” said Rick Speicher, a district sales manager with Croplan Genetics in Twin Falls. “Knowing the genetic family helps place a hybrid in the right environment.”

During a Hytest field day held near Jerome in mid-August, Speicher showed growers some of the differences between four genetic families and discussed how those backgrounds influence hybrids developed from them. The genetic families are known by geographic names and have characteristics derived from the climate: northern, southern, eastern, and western.

In the days before hybrids, growers selected ears from plants that did well to plant back the following year, Speicher said. That allowed corn plants to evolve to meet specific environmental conditions.

Northerns were selected in Minnesota and are characterized by penetrating roots that can handle sandy to clay soils. Hybrids developed from northerns tend to produce well at higher plant populations.

Southerns come from Missouri and handle sandy loam soils. Corn hybrids with southern genetics tend to do well on lighter soils north of the Snake River and where center-pivot-irrigation systems are common., Speicher said. Southerns also tend to have a long ear and do well at planting rates between 30,000 and 36,000 plants per acre.

Easterns were selected in Ohio where lake-effect moisture dominates the climate and clay soil encourage penetrating roots. Easterns tend not to do well on sandy soils unless a grower has excellent irrigation management.

Westerns are the least-used genetic family, but are the most stress tolerant. Westerns came from the western Corn Belt under rain-fed conditions. Over the years, growers in the western Corn Belt selected big ears from small plants. Around Nampa, Speicher has seen corn hybrids with western genetics fill kernels while hybrids from other genetic families had blanks. But westerns don’t handle calcareous soils well, which has limited their appeal to southern Idaho growers. Speicher said paying close attention to fertilization — especially potash and phosphorus — is key when growing hybrids derived from western genetics.

The so-called “leafies” — hybrids developed specifically for silage — aren’t a genetic family like the northerns, southerns, easterns and westerns, but they are finding a place in southern Idaho. Leafies have three to four extra leaves per plant, which helps produce lots of tonnage with good fiber digestibility. Regular corn hybrids have seven to eight leaves per plant; the leafies often have 10 to 12 leaves. Each leaf takes about three days to come out.

One disadvantage of planting leafies is that the hybrids are more susceptible to early frost, even though the plants can fill grain about 15 days earlier than regular hybrids.

Speicher told growers to plant leafies early and let the corn kernels get to half milk line before harvesting to maximize tonnage and quality.

And while growers like to see tall corn silage plants, Speicher said that’s not the best indication of silage quality or yield. He has a test plot near Jerome where he planted four different hybrids at two different planting dates: May 9 and May 26. Consistently, the later-planted rows of each hybrid were taller than the earlier-planted rows.

Speicher said that’s because the later-planted corn emerges when temperatures are warmer and day length is longer. More sunlight encourages the plant to put on more vegetative development. But while the plants are taller, the stalks are thinner, the roots more shallow and the kernels less deep on the ear. That combination can hurt yields and quality.

Corn planted earlier will have more grain fill but shorter plants.

“Do not evaluate corn fields from the highway going fifty miles per hour,” he said. “You’ll be so attracted to height that you’ll think your neighbor’s field has caught up or passed yours. Yes, it has passed it in height but not in dry-matter accumulation and probably not in fodder quality.”

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