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What ailed corn in 2010?

Illinois corn yielded less
than expected in most areas in 2010, and corn following corn was particularly
hard hit. Because current crop acreages are skewed toward corn, at least 20
percent of the 2010 corn in Illinois followed corn.

“This follows a period of several years during which corn following corn has
often yielded about the same as corn following soybean,” Nafziger said. “It has
been common, particularly in the corn rootworm variant areas of Illinois, to
have yields of corn following corn to be as high as those of corn following
soybean, especially since the advent of rootworm resistance traits. For many
producers, lower yields of corn following corn come as a shock.”

Corn following corn was challenged from the start, Nafziger said.

“In many fields, corn never looked very good,” he said. “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.”

Nafziger said that a number of factors contributed to disappointing yields of
corn following corn.

“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.”

The nice stretch of April weather to get the crop planted helped, but soil
conditions were not great, especially in fields where pre-plant nitrogen was
applied and/or more tillage was done.

Soil temperatures didn’t increase until after mid-May, Nafziger said. The corn
crop was up by then, but in many fields was already uneven and sickly appearing.

“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 said. “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.”

As well, tilled corn-on-corn fields were more likely to take in rain that fell
in May and June, causing soils to remain cool and slowing drying rates.

“Because of this, 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, and this led to stress and kernel abortion. Adding to this
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.

By Jennifer Shike, College of
Agricultural, Consumer and Environmental Sciences, University of Illinois

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