Corn hybrid variety trials at two Illinois locations in 2006 showed that hybrids with the Bt rootworm transgenic trait yielded significantly better than non-Bt rootworm hybrids in fields planted to corn after corn, especially at one location, says Emerson Nafziger, Extension agronomist, University of Illinois. At the driest location, the average yield boost from the Bt rootworm hybrid was 100 bu./acre.

“At Monmouth, the soil insecticides didn’t seem quite up to task of protecting yields under dry conditions for corn after corn,” says Nafziger. “The average yield with a rootworm Bt hybrid was 183 bu./acre. Without the Bt rootworm trait, the average was about 80 bu./acre.”

Hybrid trials at Champaign also showed a fairly significant yield difference between two different hybrid pairs on corn after corn. “In our hybrid trial at Champaign, 15 rootworm Bt hybrids yielded an average of 210 bu./acre in corn following corn and 16 hybrids without rootworm Bt yielded 186 bu./acre in the same trial,” he says. “In the trial where corn followed soybeans, the Bt RW hybrids yielded the same 210 bu./acre and the non-Bt ones averaged 195 bu./acre.”

The bottom line is that with corn following corn, any stress is magnified, says Nafziger. “In the Monmouth area, even with fairly moderate rootworm numbers, there was a considerable amount of stress due to dry conditions in June and July,” he says. “We think that hybrids with better root systems held out a little longer under these conditions, and so they pollinated much better than those without good root systems.”

A third corn after corn hybrid trial at DeKalb showed only a mild yield boost from Bt rootworm hybrids compared to their non-Bt counterparts, notes Nafzier. Yield variations differ by year and by location, he adds. However, last year showed how sensitive to stress corn can be when planted after corn.

“We’ve seen yield reductions fairly commonly in corn following corn for quite a few years, and in some cases the difference has been large,” he says. “Now, the Bt rootworm hybrids offer at least a partial solution to the typical yield reduction that occurs in corn after corn.”

For more information on the 2006 U. of I. variety trials on corn after corn, click on the following U of I Web link »
For more information on growing corn after corn, visit the following The Corn And Soybean Digest Web link »

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