Harvest delays caused by the onslaught of wet and unusually cold October weather are adding another stress to this year's predicted near-record corn crop. Conditions are ripe for stalk lodging, says Dan Froehlich, agronomist with The Mosaic Co.
"There are a number of factors that contribute to stalk lodging, and this year, conditions have been right. The odds are stacking up against the crop," Froehlich says. "The cool growing season resulted in corn plants that were taller than normal and heavily vegetated with large ears.
"Toward the end of the season as the crop approached black layer, dry conditions across much of the Corn Belt put moisture stress on plants which caused them to rob nutrients from the stalks to complete ear fill, weakening stalks."
Quite often, weak stalks are a result of the plant cannibalizing and remobilizing sugars out of the lower stalk to feed the ear. This stress, coupled with other less evident issues such as disease and soil nutrient imbalances or deficiencies, add up to a precarious situation.
"It can be easy to forget the importance of sound management as the season progresses, but hybrid selection for stalk strength and disease resistance, as well as cultural practices such as rotation and a proper nutrition program play important roles literally until the crop is in the bin," Froehlich says.
In addition to choosing genetics that offer disease resistance and season-long standability, giving the crop the right nutrition ensures plants will perform to their full potential to yield and stand through harvest.
"Nutrient imbalances and/or deficiencies predispose corn plants to stalk rot and stalk lodging. Growers who built their nutrition program around nitrogen this year and limited other nutrients to control costs, may have fields that are at higher risk for stalk lodging," Froehlich says.
For example, Froehlich says where growers applied high nitrogen levels but cut back or omitted potassium, stalk rot may be more prevalent. High nitrogen levels enhance lush vegetative growth, while low potassium levels increase the amount of premature stalk death.
On the flip side, low levels of soil nitrogen may result in less vigorous plants which put all their available energy into producing grain. This leaves the stalk vulnerable to stalk rot organisms and, ultimately, stalk lodging.
As wet conditions delay the combines, monitoring fields for potential stalk lodging will help growers manage their harvest to avoid or minimize losses. Froehlich says there are a couple of ways to look for signs of stalk quality issues — pinch or push.
First, inspect susceptible fields regularly, checking plants within the field away from the outside rows. Be sure to choose your sampling areas to adequately reflect soil types, soil drainage patterns, hybrids, rainfall differences and soil fertility levels.
To estimate how much stalk rot is present, pinch stalks near the ground and up toward the ear on a number of plants in a sampling area. A hollow shell that collapses easily means advanced stages of stalk rot.
The second method involves pushing the stalks to check their resistance and flexibility. If a plant can be pushed away to arms' length without breaking and it returns to upright when released, it's likely healthy enough to stand through harvest.
If a stalk-quality problem is identified, there are several harvest options.
1. Harvest the affected areas first. Don't let problem fields remain unharvested any longer than absolutely necessary, particularly when the grain is physiologically mature.
2. Harvest the affected areas slower than usual. Where stalks are weak or already lodging, harvest corn at a slower speed to avoid knocking corn down and to pick up lodged ears. Gathering-chain speeds and snapping-roll velocity should be correspondingly reduced to match ground speed. Run combine snouts and gathering chains as low as possible to pick up downed corn.
3. Under severe stalk lodging conditions, harvest against the direction of the lodging. Consider adjusting combine gathering chains and rolls inward as close as possible to grip rotten stalks.
The 2010 harvest is a long time away, but to avoid future harvest losses, now is the time to think about why certain fields or areas of fields exhibited weak stalks or lodged, Forehlich says.
Were the best choices made in regard to hybrid selection, fertility levels, plant populations, pest control or cultural practices? If not, he says you should identify which factors can be changed to avoid challenges next year?
"Harvest is certainly a great time to schedule soil testing for the coming year's crop," Froehlich says. "With 40% to 60% of yield related to fertility management, knowing the level of soil nutrients available is critical to providing next year's crop with the nutrition it will need for optimum yield and profitability."