The continuous corn yield penalty has yet to be solved. Decades of field trials throughout the Corn Belt show average continuous corn yield losses of 10-20%, says Joe Lauer. But losses can be much greater in bad-weather years.

Crop rotation is the only certain way to eliminate the continuous corn yield penalty, says Joe Lauer, University of Wisconsin corn agronomist. But tillage and good residue management can reduce it. “There’s an idea that you can overcome the continuous corn yield penalty” with intensive management, he adds, but we don’t find any research evidence for it.”

The 2012 growing season marked the third consecutive year of unusually high continuous-corn yield penalties in the Midwest, says Laura Gentry, University of Illinois soil scientist. Continuous corn yields in many places “were 30-50 bushels per acre less than corn following soybean.”

 

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The causes of the continuous corn yield penalty are still a bit of a mystery. The Illinois study found that the best predictors of the yield penalty in any given year are N availability, number of years in continuous corn, and weather (see sidebar).

Fred Curtin agrees. He raises corn and cattle near Stonington, Ill., with his brother and son. Since 2000, the Curtins’ operation has been 95% corn. When the weather cooperates, they see little yield drag from continuous corn, harvesting 200-240-bushel corn crops. In recent years, though, he estimates that continuous corn yields have lagged rotated corn by about 25 bushels per acre due to less-favorable weather.