Drought conditions make it easy to spot problems so you can fix them for next season. They’re also an opportunity to produce yield maps that will be valuable in future stressful seasons and variable-rate application.
Understanding the effects of drought can help set the stage for a bumper crop next year
Raising top corn yields, and turning a profit, is essentially a matter of dealing with crop stress—either avoiding it or minimizing its impact. Right now, most farmers are dealing with the results of drought and extreme heat. The only upside to the situation is that it can provide insight to help you grow a bumper crop next year, weather permitting.
If you take a close look, you probably will notice that all of your fields have not been equally stressed, says Farm Journal Field Agronomist Ken Ferrie. With harvest under way or just around the corner, it’s time to take stock of your fields.
Ferrie suggests a four-step process: First, locate your worst problem areas; second, determine the real cause of the stress (it might be more than drought); third, plan your harvest strategy;
and fourth, fix the problems revealed during your inventory.
You need to scout your fields—but not randomly. "Zero in on stressed areas by studying yield maps and NDVI [Normalized Difference Vegetation Index] maps for the current crop and from previous drought years," Ferrie says. "They will show you where to look for problems."
While all your fields were stressed by the lack of water, other problems might have worsened the effect. "You must identify those other stress points too," Ferrie says.
Stress multipliers. Likely stress multipliers include nutrient deficiencies, physical problems in the soil and pests.
"If corn experienced even a moderate nitrogen deficiency, the effects will show up severely under drought conditions," Ferrie says. The symptom is yellowing that starts at the tip of the leaf and runs down the center midrib.
In the less-stressed area of a field, count the green leaves below the ear and note how many have no nitrogen (N) deficiency symptoms. Compare this number to the equivalent number for plants in the more stressed area.
Other ways to identify N deficiency include sending plants to a lab for tissue testing and testing soil samples for nitrate content. "If you find a deficiency, plan to improve your nitrogen management in 2013," Ferrie says.
Also look for signs of potassium (K) deficiency. "Dry weather makes it hard for plants to take up potassium, especially if soil levels are low," Ferrie says. "It’s too late to fix potassium problems this year, but you want to make sure you never enter another drought season with soil levels below optimum."
With K deficiency, and also N deficiency, you should split the stalk from five nodes up downward through the crown and examine stalk quality.
"When a corn plant is unable to get nutrients from soil, it cannibalizes itself," Ferrie explains. "You see firing of leaves, and cottony pith moves down the stalk.
- September 2012