Most producers across the Corn Belt are busy planting their 1999 corn crop. In some cases, cool, wet weather could hamper and delay planting, limiting the number of growing days until harvest and causing some growers to consider earlier maturing hybrids.

But long-term research from Pioneer Hi-Bred International, Inc., as well as studies from several universities, shows that adapted, full-season corn hybrids often offer the best yield and profit advantage in these situations.

"Full-season hybrids typically make full use of a growing season," says Raj Iragavarapu, agronomy research information specialist with Pioneer. "However, even when planted late, these hybrids often outperform early maturing hybrids, adjusting their growth and development to reach maturity in a shortened growing season."

According to Iragavarapu, early hybrids should be used under certain late-plant or replant situations. But it may be best to wait a little longer before switching to these earlier products.

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

University research shows that full-season hybrids adjust to late planting with a reduction in growing degree units (GDUs) of up to six units per day of planting delay. Averaged over all hybrids, locations and years, 240 fewer heat units were required when planting was delayed 40 days from the optimum planting date.

Twelve years of 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 1998. 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 gives growers more relevant planting information for the different regions in which they farm.

For example, in the central Corn Belt, results indicate that late-April planting is best for optimum corn yield potential. Full-season hybrids – hybrids with a comparative relative maturity (CRM) of 110 or later – yield better and produce better grain at harvest than early maturity hybrids. Growers should not consider switching to earlier CRM hybrids until the first week of June.

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

Maturity planning is most critical in northern-most states because of the risk of cool weather or early frost. Pioneer recommends producers in these regions stick with full-season hybrids (100+ CRM) until the 25th of May. Growers with questions about specific hybrid characteristics and
environmental effects should talk to their seed sales professionals.

Pioneer Hi-Bred International, Inc., (NYSE-PHB) is the world's leading supplier of agricultural genetics and is the leading developer and integrator of agricultural technology. Headquartered in Des Moines, Iowa, Pioneer develops, produces and markets a full line of seeds, forage and grain
additives and services to grain and livestock producers, grain processors and other customers worldwide.

Company news release
N1867