Corn after Beans Yields More than Corn after Corn - True or False?

Last year's plots were exception to the rule.

Published on: Feb 9, 2009

This isn't a trick question. If you answered true, you're on the side of what most agronomists would say. They're saying it strongly this winter since it also works in reverse- beans after corn typically yields more than beans after beans. Coffee shop talk, at least, has many farmers considering growing some beans after beans to lower their input cost bill this spring. Crop rotation has its benefits, whether it's to get away from corn after corn or soybeans after soybeans.

Purdue University amassed some pretty convincing data last year that corn after corn required more N and yielded less at the same time. Typical recommendations call for up to 30 pounds more N per acre in corn after corn vs. if you're planting corn following soybeans or a legume forage crop.

So what's the point? There's always the exception. In the Corn Illustrated plots in '08, in the high yield project trial, both hybrids were planted after soybeans, then planted after corn. The corn stubble and soybeans stubble lay side by side. One hybrid outperformed the other in both cases. And in both cases, the yield was slightly higher for corn after corn than corn after soybeans.

Dave Nanda, agronomist and plant breeder, plus president of Bird Hybrids, Tiffin, Ohio, tried to make sense out of the results. One thing about doing research, he says, is that you have to be ready for the unexpected. Not every experiment comes out as you expect it to. Sometimes that's how you learn new things, he adds.

First and foremost, there was an abundance of nitrogen applied on this plot. Total nitrogen applied over the entire plot reached about 260 pounds per acre. That was done because this was a high-yield plot where the goal was reaching maximum agronomic yield. The extra boost of N was applied to make sure that it was not a limiting factor. There was no firing or other signs of N deficiency in any of these plots, either after corn or after soybeans.

Since there was plenty of N, that removes a major factor that sometimes limits yields in corn after corn, Nanda observes. Often farmers don't bump the rate enough for corn after corn, if they bump it at all. But 260 pounds per acre should be sufficient in either case at these yield levels. The top treatments in the plot topped out at 200 bushels per acre.

Beyond that, Nanda is less confident about what might have happened. There was variation in the soils, and a drowned-out area in the back of the plot. It's possible there was enough variation from the corn after corn side to the corn after beans side to cause experimental error.

And it's also possible that the difference linked back to stand establishment. Normally most think it would be easier to establish a stand in bean stubble. But this wasn't a normal year. About 17 inches of rain fell on the plant approximately 10 days after planting.

The bottom line is this- in this case, at least, corn after corn did yield more than corn after soybeans.