Increased corn demand and resulting higher corn prices have caused some growers to consider planting more corn-after-corn acres in 2007. Farmers who choose that route may have to shift their thinking regarding field challenges.
For instance, planting corn after corn holds the possibility of facing cool, wet soils at planting, increased disease and insect levels and high crop residue. Agronomists say one way to manage these challenges is by selecting hybrids with high ratings for stress emergence, high residue suitability, resistance to leaf, ear and stalk diseases, and stalk and root strength.
"Choose the highest performing genetics with defensive traits required for a corn-after-corn production system," advises Steve Butzen, Pioneer agronomy information manager. "That is in addition to selecting hybrid maturities that match corn planting dates and seasonal growing degree units – while accounting for cooler soils and slower emergence under corn residue."
Ratings to consider for corn after corn
Planting more corn-after-corn acres can lead to earlier planting dates. Earlier planting and reduced tillage can make the seedbed a hostile environment for stand establishment. Pioneer provides a stress emergence rating that characterizes the genetic potential of hybrids to emerge under stressful conditions – cold, wet soils or short periods of severe low temperatures.
Butzen says high-residue cropping systems, including no-till and strip-till, are increasing because of a desire to reduce input costs, manage more acres, conserve soil and moisture in dry areas and comply with government conservation programs.
"High-residue fields typically have cooler, wetter soils at planting and higher disease levels," notes Butzen. "This combination of factors can reduce stands, leaf health, stalk and ear quality and harvestable yield – but appropriate hybrids can overcome these issues."
High residue fields harbor disease
Pioneer researchers have assigned a High Residue Suitability rating to all of that company's corn hybrids. This rating gives customers guidance on selecting hybrids suitable to high-residue tillage systems.
The incidence and severity of corn diseases have increased in recent years due to build-up of crop residue. Pathogens survive in corn residue, and disease builds up over time. In fields with a history of leaf, ear or stalk diseases it is important to choose hybrids with resistance to these diseases.
In corn-after-corn situations, you need to select hybrids with resistance to common corn leaf diseases, including northern and southern leaf blight, gray leaf spot, common and southern rust and eyespot. Ear disease scores include Fusarium, Gibberella and Diplodia.
Corn may need to stand in field longer
With more corn acres to harvest, stalks may need to stand longer. Overall stalk strength can be a hedge against late-season lodging. Stalk and root strength ratings of hybrids also are available from seed companies.
In addition to selecting hybrids with good root strength, control of corn rootworm (CRW) is critical in corn-after-corn fields. Pioneer hybrids with the Herculex RW and Herculex XTRA insect traits are highly effective for protecting against western, northern and Mexican CRW, says Butzen. Herculex XTRA provides additional protection against other corn-after-corn insects – European corn borer (ECB), western bean cutworm (WBC) and black cutworm (BCW). ECB and WBC are a concern for corn-after-corn fields because they overwinter in corn residue. BCW target high-residue fields for egg-laying as they migrate from the South.