by Jennifer Shike, University of Illinois
The word for corn yields this year can be wrapped up with one word: variable. Still, when University of Illinois extension agronomist Emerson Nafziger sizes up the 2010 season, he sees one trend that stands out. Corn that followed corn was particularly hard hit.
At least 20% of the 2010 Illinois corn crop was planted in corn the previous year. “This follows a period of several years during which corn following corn has often yielded about the same as corn following soybean,” Nafziger says. But he says the corn was challenged from the very start.
“In many fields, corn never looked very good,” he says. “Compared to corn following soybean, emergence was uneven, crop color was poor, and the crop struggled to take up enough nitrogen to grow well, regardless of nitrogen rates and management. With May and June being so wet, many who waited to apply nitrogen until after planting struggled to get it applied on time. Nitrogen availability was an issue in these fields, but also in fields where N was applied on time.”
He says corn after corn suffered from a number of factors. “Soils were too wet to do a good job of tillage, whether we did that last fall or this spring, and more than the usual amount of residue remained on the surface,” he said. “Soils were wet and fairly cold coming into April. The surface residue and cool, wet soil conditions combined to get the crop off to a tough start.”
A nice stretch of April weather got the crop in the ground, but soil conditions were less than ideal, especially in fields where pre-plant nitrogen was applied and/or more tillage was done. Soil temperatures didn’t increase until after mid-May, but the corn had already emerged unevenly.
“We think that corn following corn, especially in cool, wet soils, tends to be affected by where its roots are in relation to last year’s residue, including root remnants,” he says. “Much of the residue was not buried well, and it's likely that many new-crop roots were close to old-crop residue. Residue after the fall and winter was unusually well preserved into the spring of 2010, and this could have contributed to the problem.”
Tilled corn-on-corn fields also struggled to warm up and dry out after the May and June rains. “I believe roots were damaged early and may never have recovered fully,” Nafziger said. “This probably reduced the ability of root systems to take up water and nutrients, especially nitrogen.”
As soils warmed up, the breakdown of old crop residue likely tied up nitrogen quickly. The crop was growing fast at that point and needed a lot of nitrogen, which would have been slow to release from the residue.
When excessive water damaged these root systems, plants couldn’t take up enough water and nutrients, which ultimately led to stress and kernel abortion. Add the hot, dry weather in mid-August, and we ended up with lower-than-expected kernel numbers and reduced filling rates during much of the grain-filling period.
For more information, check out the October 7 edition of The Bulletin
, an online publication written by U of I Extension specialists in crop science,at http://ipm.illinois.edu/bulletin/.