Steve Norberg wonders if growers will be physically able to mow, field-dry and bale 7-10 tons of hay per acre in a single cutting.

That’s his biggest concern about the feasibility of growing irrigated soybeans for hay production. In two years of research, he found that one cutting of the annual legume can deliver almost as much tonnage as alfalfa cut four times.

“The range for the two years was from 4 to 10.5 tons of dry matter per acre,” says Norberg, a Washington State University regional Extension specialist. “Averaged over treatments and years, we harvested 7 tons/acre. So let’s start with 7 tons. I’m about ready to turn it over to a farmer and say, ‘Can you put up that much hay in one cutting?’ ”

The quality data hasn’t been analyzed yet, but he expects it to show that soybean forage can be fed much like alfalfa.

Soybeans would work well as a rotation crop between plantings of alfalfa, timothy or another grass, he thinks. But he foresees them used primarily as an annual-legume alternative to alfalfa. A preliminary economic analysis revealed that 7-ton/acre soybeans could be as profitable as 8-ton/acre alfalfa even with a discounted soybean-hay price, he reports.

Norberg began evaluating soybeans while trying to find a way to reduce haying costs. “I was looking at the budget for hay production and seeing that we spend almost $400 a year on putting up four cuttings of hay.”

The best way to cut costs was to reduce the number of cuttings, he figured, but quality goes down when alfalfa is cut fewer times. So he turned to soybeans, which he says were introduced in the U.S. as a hay crop. Their growth habit makes them well-suited to a one-cutting system, and their forage quality stays high longer than alfalfa’s.

“The nice thing about soybeans is, whenever you’re ready to cut, they’ll be ready for you,” says Norberg.

He grew four Roundup Ready varieties at Othello, WA. Similar plots were established near Logan, UT, by Earl Creech, a Utah State University Extension agronomist. They tested Asgrow 1431, a Maturity Group I variety; Asgrow 4531, a Group IV; and Large Lad and Big Fellow, tall-growing Group VII varieties from Eagle Seeds, Weiner, AR.

Planted in mid-May at 140,000 seeds per acre, the plots were harvested in early, mid- or late September. At the last harvest date, the Group I variety was fully mature, the Group IV variety had green pods with small seeds, and the two Group VIIs were flowering.

Dry matter yield of the Group I variety peaked in early September; the others continued to add yield until the last harvest. The top 2012 yields were 6.3 tons/acre for Large Lad in Utah and 6 tons/acre for Asgrow 1431 in Washington.

Norberg got better stands and higher yields in 2013 than in 2012. The lowest yield was 5.8 tons/acre for the Group I variety harvested in late September. It yielded 7.5 tons/acre early that month and had lost leaves by the later harvest date.

His 10.5 ton/acre top yield was from Big Fellow harvested in late September. The 2013 Utah results aren’t available yet.