Many farmers in Iowa like to start planting corn in mid-April and this year they've been unable to do that, due to cold, wet weather. The situation has prompted some farmers to ask questions about switching to earlier season corn hybrids--if planting delays continue and they have to plant later than anticipated.
If cool, wet weather continues to delay planting, it will limit the number of growing degree days for 2008 crop. So, at what date should you switch to planting earlier- maturing corn hybrids?
Long-term research studies by seed companies 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 fieldwork and planting, hybrid maturity switching can become an issue," says Mark Jeschke, agronomy research scientist for Pioneer Hi-Bred. "But we certainly aren't at that point yet this spring. Today is only April 23. Your decision to change hybrids should be based on the expected returns to the grower; including yield, drying cost and test weight discounts."
Don't switch to earlier hybrids too soon
According to Jeschke, early-maturing corn hybrids should be used under extreme late-plant or replant situations. But switching to earlier corn hybrids 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.
University research shows that full-season hybrids adjust to late planting with a reduction in their growing degree unit 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.
Seed company, university studies agree
Pioneer studies reinforce the university findings. Pioneer focused on studying 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 (which includes the southern half of Iowa), results indicate early to mid-April planting is best for optimum corn yield potential. Full-season hybrids (those 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, says Jeschke.
Iowa in the north-central Corn Belt region
Soil conditions permitting, April planting also is recommended in the north-central Corn Belt - which includes the northern half of Iowa and southern Minnesota. In this region, 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, he explains. Pioneer recommends farmers in northern Corn Belt areas (central Minnesota and north-central Wisconsin) stick with full-season hybrids (98 to 105 CRM) until about 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 to 100 CRM).
"Growers with questions about specific hybrid characteristics and environmental effects should talk to their seed sales professionals," advises Jeschke.