n the search for a third crop to bring profits as well as diversity to Iowa's two-crop system, one new crop has surfaced as a worthy candidate: field peas.

A project launched in 2004 by the Leopold Center's Ecology Initiative is demonstrating favorable economics for farmers who also raise hogs. Field peas are a short-season crop that can be grown either after a wheat crop or before a late planting of soybeans. Peas are used in other parts of the world as food for pigs as well as in human diets.

"It's hard to put an exact value on what it's worth for you to grow field peas, kind of like hay crops, but we thought that if we could save producers $2 a ton in livestock rations, that it would be economical for them to grow double-cropped peas with some other crop in their rotation," said Tom Miller, Iowa State University Extension livestock specialist based in Washington County in southeast Iowa. Producers also would see other benefits of longer rotations such as increased ecological diversity to break insect and pest cycles.

"One of the nice things for swine producers is that they always have an empty bin in June or July, when fall- and spring-planted peas are harvested, so they can make good use of their bin space," he added. "By the time they need their bins again in the fall, they'll have used the peas and emptied the bins."

Miller is working with ISU Extension crop specialist Jim Fawcett, who is based in nearby Johnson County. Together they are growing different varieties of field peas in several rotations and locations, and using them in swine feeding trials. Their most recent trial was for 1,200 grow-to-finish pigs raised by a large hog producer in Washington County. The project is funded by a three-year Leopold Center grant, matched by USDA-SARE funds.

Peas good source of protein for pigs
For the experiment, the pigs were divided into six groups - two as a control, two fed one variety of field pea ration and two fed a second variety of field peas. The researchers replaced roughly 400 pounds of corn and 200 pounds of soybean meal with 600 pounds of field peas. Rations were balanced for nutritional needs of pigs at various weights and adjusted appropriately for protein and energy.

Miller said each pig was weighed individually four times between September 2005 and January 2006 to determine performance. Each pig in the experimental groups consumed an average of 186 pounds of field peas, 260 pounds of corn and 60 pounds of soybean meal, at a per-pig feed savings of 67 cents. They estimated a market price for field peas at $3.50 a bushel.

"We saw no differences in the average daily gain in pigs fed a ration that included field peas," Miller said. "In fact - when considering feed efficiency - the pigs performed as good as or better on those diets than on the conventional rations."

A field day in mid-June attracted an audience of about a dozen local growers. The event was held at a 20-acre field on a private farm near Amana that had just finished blooming. The field was harvested in early July, followed by an early-maturing soybean variety. Another planting option being investigated is early maturing milo for swine rations.

"There's really no special equipment needed to grow this crop," said Fawcett as he walked through field peas, which stood about 30 inches high. "We planted April 5, but last year we planted in the snow in mid-March. They'll come up as soon as the ground gets to 40 degrees."

Research focuses on best rotation
Fawcett said they are experimenting with both spring- and fall-planted peas. He said peas in one field planted in October grew about twice as tall as the spring-planted peas, and yielded about five bushels per acre more than the spring-planted peas. He said he had hoped that fall-planted peas could be harvested a week or two sooner than spring-planted peas, but this year they both matured at about the same time.

Fawcett said yields on various plots throughout southeast Iowa averaged 30 to 55 bushels per acre in 2005. Yields in 2006 have averaged about 25 bushels per acre. The lower yields in 2006 may be partly due to the later planting date in 2006, and also because of very hot weather in late May when the peas were flowering.

He said chemicals can be used to control weeds, but late-emerging weeds such as waterhemp have not been much of a problem in spring-planted peas. However, waterhemp has been a challenge when the peas are planted in July after a winter wheat harvest. A legume, field peas fix nitrogen for the following crop, which reduces input needs. Peas also can break the insect and pest cycle in the typical corn-soybean rotation.

Two other positive aspects of field peas: the crop is eligible for loan deficiency payments and it is harvested in the summer, about the time when the price for soybean meal usually peaks.

"I'm amazed at the people who've approached us on this because it's been all up and down the scale from small, organic farmers to very large producers who market 10,000 pigs every year," Miller said.

He said that large hog producers often plant wheat just for a place to apply manure during summer months. Small producers also plant wheat for its high-quality straw, which is used as livestock bedding in hoop barns. In either case, he noted the addition of a crop of field peas can increase profitability because the crop can be fed to hogs with no further processing.