If its value as a fast-growing forage doesn't grab your attention, maybe its nitrogen-fixing abilities will.

The annual legume called grass pea — sold under the name AC Greenfix — shows real promise as a fill-in spring forage for the Great Plains, say USDA researchers. It can even be seeded with bermudagrass to boost forage quality and production.

Grass pea has shown drought tolerance and could fill the grazing gap that often occurs in May and June — after wheat is grazed but before most warm-season grasses are ready in mid- to late June. That's according to Srinivas Rao, research agronomist at USDA'sARS Grazinglands Research Lab in El Reno, OK.

“Like alfalfa, the forage quality of grass pea is highest just after flowering, which takes place 40-45 days after seeding,” says Rao. “The quality stays high until just before pod formation, so we recommend grazing the crop starting at 55-65 days after seeding.”

That means planting needs to take place in early to mid-March,he adds. “We generally have tried to plant as early as we can after the last frost date.”

Rao and colleagues also examined the effects of interseeding grass pea into bermudagrass. Benefits included improved forage quality and earlier grazing, he says.

“Grass pea provided between 45 and 90 lbs of nitrogen to the bermudagrass, which improved N concentrations in the grass, as well as raised the level of digestible dry matter.”

Forage quality was secondary to making nitrogen when the crop was introduced to the U.S. nearly a decade ago, says Ila Krause. She and husband Dave own Dakota Frontier Seeds, Flasher, ND, which has U.S. distribution rights for AC Greenfix.

“It's an excellent green manure crop and can add 100-200 lbs of nitrogen per acre to a field when it's plowed under,” says Krause.

But grass pea (also known as chickling vetch) caught on as a forage, she says, because of its high protein content — usually 22-26% — and high relative feed value and TDN levels.

“It's also extremely palatable and animals seem to love it because it's very sweet,” notes Krause. “Farmers have told us their cattle will come running when they smell the AC Greenfix bales, and they cleanup every bit.”

North Dakota State University researchers fed grass pea to gestating ewes at two locations. It produced comparable results to feeding alfalfa, they report. And, although Rao and his Oklahoma colleagues haven't conducted actual grazing trials, he says cattle seem to prefer grass pea to other grass and legume crops they've tested.

Inoculating seed is essential,adds Krause.

“And if you're going to graze or harvest the crop for forage, you really need to fertilize it properly, as you would with any forage crop. It needs enough phosphorus to produce good yields, which can top out at up to 9,000 lbs of dry matter per acre when moisture and soil conditions are right.”

Starting with clean soil is another must, says Culver, KS, farmer Rodney Hummel. “Until it gets established, the crop doesn't compete well with weeds. But after a few weeks it usually takes off. By early May, it starts to flower and that's usually when I cut it and disk it in.”

He says soil tests have shown the crop has added over 100 lbs/acre of nitrogen to his soils.

In his Kansas fields, Hummel says the crop usually grows about 30” tall. But Krause says farmers in more moist, cooler climates, such as Minnesota, report the crop often reaches 4' in height. “It grows bigger in our part of the country, but can handle drier areas, too. It's a fairly flexible legume.”

For more information, contact Dakota Frontier Seeds at 701-597-3919.