So far this fall, continuous corn is coming up pretty short compared to corn raised in a rotation with soybeans.

Initial reports from the field show that, using "reasonable" average input costs and crop yields, there's a 27-bushel/acre yield drag between continuous and rotated corn, at least in Illinois, according to University of Illinois ag economist Gary Schnitkey. It "could cause soybeans to be more profitable than corn-after-corn," he says.

Schnitkey used the following values to arrive at the 27-bushel difference:

• 165 bushel corn-after-soybean yield,
• 50 bushel per acre soybean yield,
• $6.25 per bushel price for corn,
• $13.00 per bushel price for soybeans,
• $500 per acre non-land cost for corn, and
• $290 per acre non-land cost for soybeans.

Using these numbers, Schnitkey says continuous corn needs to yield 138 bushels/acre to net the same amount as corn after soybeans.

But, that doesn't account for crop insurance costs. Drawbacks to corn-on-corn don't just stop with this year's crop, either.

"If crop insurance payments occur at yields above the break-even corn-after-corn yield, corn-after-corn will be more profitable than soybeans. If crop insurance payments occur at yields below the break-even corn-after-corn yield, crop insurance will limit difference in returns between corn and soybeans," Schnitkey says. "From a crop insurance perspective, the negative to corn-after-corn is that a lower 2011 yield will lower the APH in future years, thereby lowering the safety net provided by crop insurance."