Long-Term Research Shows Full-Season Corn Hybrids Best Choice, Even if Delayed Planting

Pioneer Hi-Bred, university studies indicate yield, profit advantage over switch to early hybrids

Growers across the Corn Belt are either anxiously waiting to get into their fields or are in the early stages of planting their 2008 corn crop. If cool, wet weather continues, planting will be delayed for many growers, limiting the number of growing days for the crop and prompting questions about switching to earlier hybrids.

But long-term research studies from Pioneer Hi-Bred, a DuPont business, and several universities show that adapted, full-season corn hybrids usually offer the best yield and profit advantage when planting delays are not extreme.

When wet weather significantly delays field work and planting, hybrid maturity switches can become an issue, says Mark Jeschke, agronomy research scientist for Pioneer. “However, hybrid changes should be based on expected grower returns including yield, drying costs and test weight discounts.”

According to Jeschke early hybrids should be used under extreme late-plant or replant situations. But switching to earlier products too soon may result in serious yield and profit penalties.

Full-season hybrids typically make full use of a growing season. Even when planted late, these hybrids often outperform early maturing hybrids, adjusting their growth and development to reach maturity in a shortened growing season.

Long-term studies by both Pioneer and universities which included a range of hybrid maturities across planting dates extending from April through June have shown a clear yield and profit advantage for full-season hybrids.

“If growers have questions about switching, including replacement hybrid availability, they should consult their Pioneer sales professional,” says Jeschke.

University research shows that full-season hybrids adjust to late planting with a reduction in their growing degree unit (GDU) requirement of up to six units per day of planting delay. For example, hybrids planted May 20 may require 150 fewer heat units to reach maturity than the same hybrids planted April 25. This adjustment reduces the risk of fall frost damage to these hybrids.

Pioneer studies reinforce the university findings. Pioneer focused on hybrids planted across the central, north-central and far-north regions of the Corn Belt from 1987 to 2004. Hybrids were planted from early April to mid-June and grouped into full, medium and early maturities at each location. The studies looked at differences in corn grain yield response to planting date, as well as moisture, test weight and gross income response. The data give growers more relevant planting information for the different regions in which they farm.

For example, in the central Corn Belt, results indicate that early to mid-April planting is best for optimum corn yield potential. Full-season hybrids - hybrids with a comparative relative maturity (CRM) of 111 to 115 - yield better and produce better grain at harvest than early maturity hybrids. Growers should not consider switching to earlier CRM hybrids until the last week of May.

Soil conditions permitting, April planting also is recommended in the north-central Corn Belt. Growers are encouraged to plant full-season hybrids (103 to 110 CRM) until the last week of May in this region.

Maturity planning is most critical in northernmost states because of the risk of cool weather or early frost. Pioneer recommends producers in northern Corn Belt areas (central Minnesota and north-central Wisconsin) stick with full-season hybrids (98-105 CRM) until approximately May 27. This recommendation also carries into far-northern areas (northern Minnesota, North Dakota and Quebec, Canada) for hybrids that are full-season there (97-100 CRM).

Growers with questions about specific hybrid characteristics and environmental effects should talk to their seed sales professionals.