Bill Fuller wasn’t satisfied with the 7-9% protein content of his corn silage and wanted to make it a more complete feed for his beef cattle.

“I wanted something to blend with corn as a protein supplement,” says Fuller, of Kinder, LA.

He began to investigate alternative protein sources when forage soybeans caught his attention. For two years, Fuller has teamed with Chip LeMieux and Bill Storer, animal scientists at McNeese State University, Lake Charles, LA, to grow, harvest and evaluate forage soybeans developed by Eagle Seed Co., Weiner, AR.

Last year they tested Big Fellow, a late-maturing Group VII Roundup Ready variety. A center-pivot-irrigated field was divided into sections for corn planted at a seeding rate of 28,000 and soybeans planted at 100,000 seeds per acre. Both were on 30” rows to match the harvester. The soybeans were planted in late March, one week ahead of the corn.

The corn reached dent stage in August and dropped to a lower moisture level than is typical for silage. That allowed the soybeans to gain more vegetative growth, reaching growth stage R5 and yielding 3.9-4.4 tons/acre of dry matter at harvest.

A pull-type forage harvester chopped both crops at a combined dry matter of about 36%. To layer the crops, corn was chopped until the silage wagon was half full, then soybeans were chopped for the remainder of the load. The two forages were mixed as they were bagged.

Fuller fed the silage free-choice to cows with calves. “I had to run the cows out,” he says. “They would eat and eat. If I let them, they’d eat over 50 lbs/day, and that is too much.”

The soybeans averaged 18-19% protein, and adding them to corn in roughly a 50-50 mix resulted in silage protein levels of 13-14%.

Fuller definitely feels he’s on the right track, although he’s quick to remind that, while soybeans are intriguing, experimenting with them remains second to producing the best silage corn possible. The row spacing, harvest timing and other details have to benefit the corn.

The corn-soybean silage also is being evaluated as part of McNeese State University’s heifer enhancement and development program. Directed by Storer and LeMieux, the program is a joint venture of the university and Fuller Farms.

Producers bring their heifers to the university feedlot for a five-month stay, LeMieux reports. Each heifer is weighed once a month. Before it leaves the feedlot, researchers evaluate it for daily gain and other characteristics that’ll determine how well it will perform as a replacement. Feeding the silage mixture to developing heifers under controlled conditions will confirm a lot about the value of soybean forage as a supplemental protein source, he adds.

So what’s ahead for soybeans as forage? LeMieux, Storer and Fuller are involved in agronomic studies to pinpoint exactly what works best in the field – everything from soybean row spacing, plant population, planting and harvest dates to the finer points of harvesting.
This year the team is evaluating Large Lad, another Group VII Roundup Ready variety, as well as an experimental Group V soybean, both produced by Eagle Seed. According to Storer, Large Lad seems to perform similar to Big Fellow in the field, both reaching heights of over 6’. The Group V tops out at about 3’ and is much bushier with greater pod development. Storer is looking closely at leaf-to-stem ratios and stalk thickness.