Economists: Corn after corn a continuous challenge for growers

With corn demand expected to rise, in part because of increased ethanol production, more farmers could consider growing corn after corn — a practice commonly referred to as "continuous" corn. There are risks and benefits for producers who choose to abandon rotating corn with soybeans, said Jess Lowenberg-DeBoer and Bruce Erickson.

Continuous corn growers should expect higher production costs and will need to produce larger-than-average yields to make the cropping practice worth their while, the economists said.

Lowenberg-DeBoer and Erickson analyzed the economic feasibility of continuous corn versus crop rotation. They found that a 3,000-acre farm in the Eastern Corn Belt with average rotational per-acre yields of 175.9 bushels for corn and 56.6 bushels for soybeans would have to produce at least 225 bushels an acre in continuous corn to meet those higher costs and still earn a profit.

Although several celebrated corn growers are producing continuous corn crops of 300 bushels an acre or more, university research has not shown a yield benefit from switching to long-term continuous corn, Lowenberg-DeBoer said. Field trials indicate growing soybeans after corn reduces disease and insect problems and provides easier management of crop residue.

"If we can show that long-term continuous corn works on a general basis, then we need to be able to show a substantially higher yield from long-term continuous corn to make it competitive with rotation soybeans," Lowenberg-DeBoer said. "It may need to be as much as 50 bushels an acre more to justify the continuous corn with higher fuel and nitrogen costs.

"If we want to talk specific numbers, then we're talking about maybe $30 an acre more in nitrogen. We also have extra costs in tillage. Fall tillage is a typical part of this system, so it might cost another $20 an acre or so. All of this adds up to — for the high-yield continuous system — costing somewhere between $80 and $100 more an acre."

The seed costs for many farmers raising continuous corn also tends to be a bit higher, said Erickson, who also is an agronomist.

"They may want to plant a hybrid with particular traits that does especially well in corn on corn, while there's a broader selection in corn following soybeans," Erickson said.

"We've also noticed that people who have been successfully raising continuous corn tend to plant at fairly high planting rates — maybe higher than would the typical producer. If you're achieving high yields planting corn after soybeans, you're planting high planting rates anyway, but there may be additional seeding costs for the high-yield continuous corn program."

The Purdue economists also found that continuous corn requires a multiyear commitment by farmers and that producers have to think differently about crop residue and soil fertility.

"When they were raising continuous corn for a number of years, it often wasn't the second or third year but after a period of years that producers seemed to get to the point where they were managing residue and returning that residue to the field with tillage," Erickson said. "It seems that the organic matter builds up and then producers are farming in a somewhat different environment than they would if they were in a typical corn-soybean rotation or short-term continuous corn."

While long-term continuous corn poses agronomic challenges for growers, crop genetics advances, ethanol and world commodity markets are making corn-on-corn production more attractive to farmers in the United States, Lowenberg-DeBoer said.

"There's strong competition from Latin American countries for soybean production," he said. "There's the slow increase in average soybean yield, especially in the Eastern Corn Belt, where corn yields have been rising quite consistently and soybeans have not. The growth of ethanol demands more corn. Technology like rootworm Bt corn has made production of continuous corn easier than it was in the past.

"Another key is that in international trade, the U.S. is very competitive in corn production. If you look at U.S. corn yields compared to those in Latin America, U.S. yields tend to be twice or three times as high. These are some of the reasons why this attention to long-term continuous corn is happening right now."

And, added Erickson, "farmers really like growing corn."

For more information about continuous corn and the Purdue economic analysis, read "Weighing the Returns of Rotated vs. Continuous Corn" by Erickson and Lowenberg-DeBoer. The paper can be downloaded online. The paper appears on Purdue's Top Farmer Crop Workshop Web site.

Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu

Sources: Jess Lowenberg-DeBoer, (765) 494-4230, lowenbej@purdue.edu

Bruce Erickson, (765) 494-9557, berickso@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
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