Is Early Planted Corn Worth the Effort?
By Bill Mahanna and Ev Thomas
Corn growers are typically aggressive in pushing planting dates given the growing number of acres that need to be planted and the desire to boost yields with today's longer season hybrids. USDA statistics indicate that average planting dates are about a week earlier than in the 1990s. Research does support that yields are less affected by planting too early rather than planting too late.
Emergence impacts yield
The yield of a particular corn hybrid is greatly influenced by stand density and uniformity. Planter maintenance and effectiveness are certainly important but so are seedbed conditions and the genetic potential of the hybrid to emerge from cold, wet soils. The trend toward reduced tillage and the accompanying higher infield residues often results in slower seedbed drying and colder soil temperatures. This can cause seed emergence stress even in Southern and Western corn growing regions.
The guideline for planting corn is to wait until soil temperatures are at least 50 F. Corn is a warm season plant with over 85 F as the optimal temperature for emergence. It is not unusual for early planted corn to take 3 weeks or longer to emerge if planted into 50 to 55 F soil temperatures compared to less than a week if planted into 70 F soils.
When water is under 50 to 55 F, abnormalities can occur. This then can cause pathogens to invade corn plants.
It takes a coordinated effort for proper emergence to occur so that the coleoptile (pointed protective sheath covering the emerging shoot) is pushed above the soil surface allowing the first leaf to unfurl. This sequence of events can be compromised if the seed absorbs (imbibes) water less than 50 to 55 F. This is termed imbibitional chilling damage where brittle cell membranes can rupture causing abnormalities such as corkscrew or fused coleoptiles. This is further aggravated by leaked cell contents inviting pathogen invasion.
The potential for cold water damage falls as seedlings emerge and if initial imbibition occurred above 50 F. This partially explains why early planted corn, followed by warm weather, tends to emerge better than later planted corn emerging into cold weather or snow cover. Emergence damage caused by cold, wet soils is generally irreversible and difficult to detect as the problems with stand density/uniformity take several weeks to become visible.
Seed companies routinely test experimental hybrids for stress emergence by planting them into a wide range of stressful (cold, no-till, corn-on-corn) environments. Some companies also employ proprietary laboratory assays for hybrid advancement decisions and to support marker-assisted breeding efforts to improve tolerance to emergence stress.
Stress emergence ratings found in seed catalogs reflect genetic variability for tolerance to environmental stresses. They are not a rating for specific disease resistance. However, injury to emerging seedlings can promote seedling disease, especially in growing environments with heavy disease pressure. Planting into warmer soils typically favors seedling growth and reduces potential for soil pathogens, such as Fusarium and Pythium. The use of seed treatments (fungicides, insecticides, biological) are extremely popular and provide protection against target organisms for 10 to 14 days after planting during which the seed has a high vulnerability to infection.
Early plant considerations
Timing of planting has the biggest impact on stand establishment. Soil temperature, seedbed condition (moisture) and weather following planting are also key elements in the successful emergence of any hybrid.
Early plantings have a better chance of success in well-drained soils with limited residue cover. Selecting hybrids with high stress emergence ratings and using premium seed treatments can provide critical protection in stressful environments.
Used by permission from the April 2013 issue of Hoard’s Dairyman.
Copyright 2013 by W.D. Hoard & Sons Company, Fort Atkinson, Wisconsin.