Don't Expect a Massive Corn Yield Hit

Don't Expect a Massive Corn Yield Hit

U of I's Emerson Nafziger says the conditions surrounding 2010 made for a larger than normal yield hit in corn-after-corn fields.

The 2010 season was a disappointing one for corn growers in many parts of Illinois, says University of Illinois Extension agronomist Emerson Nafziger.

With a statewide average yield of only 157 bushels per acre, just 4.2 bushels higher than the U.S. average, and the third-worst yield in the past decade, many Illinois producers are hoping for a more bountiful 2011.

Over the past 10 years, the Illinois corn yield has averaged 13.7 bushels per acre above the U.S. national average, and has been below the national average only once (by 4.9 bushels in 2005) and above it by as much as 25.1 bushels (2008).

"The major problem in 2010 was heavy rainfall in June that resulted in standing water and saturated soils, which in turn resulted in nitrogen loss and damage to root systems which could not be repaired," Nafziger adds. "As a result, affected fields and parts of fields ended up with shortages of both nitrogen and water, problems made worse by high temperatures and early maturity, and in some cases by dry weather during the latter part of the grainfilling period."

Corn following corn was particularly hard hit in 2010, and there were numerous reports of larger yield penalties for corn following corn compared to corn following soybean than most have seen for a number of years, he added.

In research trials conducted since 2003, Nafziger saw similar results. He has been comparing continuous corn, corn rotated with soybean, and corn following either corn or soybean in a corn-corn-soybean rotation.

According to Nafziger, the rule of thumb for many years has been that corn following corn yields are about 10% less than corn following soybean. This difference has often been less than that in some recent comparisons, but varies depending on the year.

Across four northern Illinois sites, the yield penalty for continuous corn was about 11% in 2008-09, but 19% in 2010. Second-year corn in the corn-corn-soybean rotation yielded only 5% less than corn following soybean in 2008-09, and 10% less in 2010, indicating that having soybeans even two years ago helps lessen the yield penalty for corn following corn. At the two southern Illinois locations, with considerably lower yields, the penalty for continuous compared to rotated corn was substantially less, measured either as bushels or as a percentage.

Despite the relatively poor performance of corn following corn in 2010, Nafziger says most indications are that this shouldn't be the expectation for 2011.

"Field and soil conditions are much different than they were a year ago," he adds. "None of the factors of a year ago – late fall harvest, poor tillage conditions, lots of fresh residue on the surface, and much nitrogen yet to apply – exist this spring. We did a massive amount of tillage last fall, in some cases perhaps more than was necessary."

One additional benefit for producers is that it has not been wet for extended periods when soil temperatures were warm since nitrogen was applied last fall. Most of the nitrogen should still be present, with a good deal of it still in the ammonium form and so not subject to loss.

Waiting until soils are dry enough at depth (not just over the surface) will help minimize compaction effects, as will using controlled traffic, making fewer tillage passes, and lowering tire pressure.

Nafziger encourages producers to follow the same practices they have been using when planting corn following corn this year.

"Our research shows that both corn after corn and corn after soybean respond similarly to planting date and to plant population, so those should change only as soil conditions and productivity might indicate," he explains. "We've never been able to identify hybrids that do consistently better in corn following corn, though corn following corn may tend to experience stress (primarily drought stress) and foliar diseases more often, so that should be factored in."

TAGS: Soybean
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