Minnesotan mixes corn and soybeans in windrows.

Allan Wake always wanted to make corn silage early, before northern Minnesota's fall weather made fields too wet for chopping.

“That's our biggest enemy of corn silage,” says Wake, of Federal Dam. “Sometimes we have to wait for the ground to freeze to get our corn off.”

Wake has reached his early harvest goal, while adding protein to the silage in the field. In 1999 and 2000, he grew Roundup Ready corn and soybeans side by side. He mowed and conditioned the two crops in late August, and field-dried the windrows to 60% moisture before chopping them.

The corn-bean mix made good silage both years, last year testing 16.8% crude protein. It's very palatable, too.

“My cattle love it,” says Wake, who raises beef calves.

He planted a Group II soybean variety and a 96-day hybrid. He chose a late-maturing hybrid because he didn't want fully developed ears, figuring the conditioning rolls would snap them off and they'd be lost.

Although planters are available that could plant the two crops simultaneously, Wake used a four-row planter and a grain drill. First he planted the corn, filling just the two outside seed boxes. That put pairs of corn rows 15-20" apart with about 8' in between. Then he drilled soybeans into those spaces.

High seed costs may be the biggest drawback to this cropping method, says Wake. He used high planting rates for both crops, and Roundup Ready seed is expensive.

Wake fertilized the corn when he planted, and broadcast 30 lbs per acre of nitrogen to help get the beans started. One application of Roundup, when the corn, soybeans and quackgrass all were about 8" tall, cleaned up the field.

“I got 99% control of all weed species,” he says.

When he cut the crops with a disc mower-conditioner, the soybeans had pods but no beans, and the corn was starting to form ears. Traveling crosswise, the mower-conditioner cut both crops clean and formed windrows with corn and soybean plants mixed evenly.

“It's a little scary heading into 10-12'-high corn for the first time with a tractor and mower-conditioner, but it worked out fine,” says Wake.

“I was amazed at how fast that mass of material dried,” he adds. “I wanted to put it up at 65-70% moisture, but it dried to 55% in three days.”

It yielded 6.2 tons of silage per acre — high for northern Minnesota, says Wake.

He figures growing corn and soybeans side by side for silage would be especially beneficial for dairy farmers. It would simplify their cropping programs and supply almost a complete ration for year-round feeding.

“They could do away with mixer wagons because it's almost 100% homogeneous,” he says.

Corn-soybean silage is a “really good” feed for dairy cattle, agrees Dan Undersander, University of Wisconsin extension forage agronomist. But he thinks lupins may make a better corn companion than soybeans in northern Minnesota, because they grow better in cool weather.

“We've done some work with lupins, and they certainly are a good forage,” he says.

Chopping corn before ears form, like Wake did, is okay, says Undersander.

“The data suggest that, if he harvested near to when the ears would have formed, he probably lost very little in quality.”

The biggest quality concern is NDF, which in Wake's 2000 corn-bean silage was 49.5% — higher than corn silage's normal level. According to Undersander, that probably was because the silage didn't have grain to dilute the corn stover's high NDF level.

If the silage was fed to milk cows, supplemental grain likely would be needed to lower the NDF and bump up the energy, he says.