Two new tall-growing forage soybean varieties still look awesome to Rebecca Atkinson, Southern Illinois University beef forage specialist.

They performed well in an on-farm rotational grazing study in 2009, her second year of testing, and one of the varieties yielded almost 6 tons/acre of hay when planted after last summer's wheat harvest.

Results from a silage test at Andrews University, Berrien Springs, MI, were less spectacular, but Dayle Birney, crops manager at the university's dairy, was satisfied. He harvested 10 tons/acre of soybean silage testing 14% protein, 41% ADF and 51% NDF. He grew 10 acres of the soybeans, and if the silage performs satisfactorily in rations for the 600-cow herd, he'll plant 40 acres this year.

“The jury's still out,” says Birney. “We're going to see how good a replacement it is for alfalfa silage.”

The Roundup Ready varieties — Large Lad and Big Fellow — were developed at Eagle Seed Co., Weiner, AR, primarily for use in wildlife food plots. They were tested as forage crops at three universities in 2008, and the results were reported in the March 2009 issue of Hay & Forage Grower (see our story, “They're Awesome”).

The soybeans were evaluated at several additional locations last year. Although they're long-season, Group 7 varieties, they can be grown anywhere in the U.S., says Brad Doyle, Eagle Seed general manager.

Doyle sees them as a promising alternative to alfalfa, especially for farmers who can't grow the perennial legume. Lab tests have shown the soybeans' leaves have up to 42% protein, he says.

In Illinois, Atkinson is interested in them mostly as a pasture crop for cow-calf producers. Yields were impressive in a 2008 simulated grazing study, with Big Fellow peaking at 9.6 tons of dry matter per acre and Large Lad at 8.9 tons/acre. So last year she convinced a producer to plant 2 acres of the soybeans in one of 12 paddocks in his rotational grazing system.

“I instructed him to graze it down to 10” but not past that, and that's what he did,” she reports.

The producer grazed the paddock twice, but didn't apply glyphosate, so weeds took over after the second grazing. If he had sprayed, he could have gotten at least one more grazing, she says.

He usually rotates his cattle every three days, but soybean growth was so great that he left them in that paddock an extra day.

“He was so impressed with them that he's going to plant 4 acres next summer to graze his cattle on again,” says Atkinson.

In the double-crop hay trial, the beans were planted in 15” rows June 29 and mowed into windrows when they were 3-4' tall. The yield was exceptional, but field drying was problematic, says Atkinson. The soybean stems weren't conditioned severely enough, and it took several days to get the crop dry enough to bale.

She plans further work to find out how much conditioning is needed. Wider windrows should speed drying, too, and narrower rows might result in smaller stems that dry faster, she says.

In the Michigan silage trial, Birney planted half the 10 acres to each of the varieties and mowed the crop into windrows after last fall's first frost. The beans were about 5' tall, and since both varieties are indeterminate, plant tops had new growth while the bottoms were more mature.

“We had everything from blooming and putting on new leaves down to pods,” says Birney.

“It had monster leaves and the silage smells just like alfalfa silage,” he adds.

He also tried planting forage soybeans and corn together, hoping the resulting silage would be high in both energy and protein.

“That wasn't a real good thing; harvesting was a pain,” says Birney. The soybean plants stayed mostly close to the ground, and the chopper's all-crop head couldn't get them all. Also, the beans were much higher in moisture than the corn.

Eagle Seed's Doyle has tried growing the soybeans with various other species and doesn't recommend it.

“When two species are planted together, one will act like a weed and steal nutrients, light and moisture from the other,” he points out. If you want to try it, he adds, “make sure you do a planting-rate study first, and keep the soybeans by themselves as a check.”

Planting the soybeans with pearl millet didn't work well in Idaho, reports Christi Falen, University of Idaho extension educator in Lincoln County. A producer was hoping to extend the grazing season and increase the pasture's protein content compared with pearl millet alone. That warm-season annual had already been found to be well-suited for late-season grazing.

The mixture, planted in June, was grazed in early August and again in the fall.

The soybeans “didn't hold up well under conditions for us, where the (irrigation) water is in a gravity situation,” Falen reports.

Also, the soybean plants didn't stand sufficiently for late-fall grazing, she says.

For more information, contact Doyle at 870-684-7377 or brad@eagleseed.com.