A team of scientists from the University of Idaho's Aberdeen Research and Extension Center is helping potato growers at the Fort Hall Indian Reservation evaluate the costs and benefits of green-manure crops and determine the best methods for producing them.

Grown for a period of weeks after the fall wheat harvest, green manures are increasingly being chopped and incorporated into Idaho fields to improve their soils' physical, chemical and biological properties and to reduce pest problems in the following year's potatoes.

Tom Liddil, agricultural resources manager with the Shoshone-Bannock Tribes, estimates that 5,000 to 10,000 acres of the reservation's 290,000 acres of croplands are currently being treated with green manures.

This is the first time, however, that the practice has been studied so comprehensively on the reservation. Pamela Hutchinson, a UI potato cropping systems weed scientist, is coordinating the university's contributions to the study.

She wants to measure the costs associated with growing successful, beneficial green-manure crops and to determine whether the reservation's potato growers can use them as an integrated pest management tool that compliments--and possibly reduces--agricultural chemical inputs without jeopardizing profits.

The UI scientists will take before-and-after measurements of soil characteristics and pest problems in a wheat-potato rotation supplemented with at least three different kinds of green manures, including a white mustard and blends of white and brown mustards. They'll document how these mustards compare with synthetic soil fumigants for nematode control, examine their impacts on soil fertility and nutrient cycling, and measure their effects on wireworms, weeds and potato diseases.

"We'll be able to help them get a start on adjusting nutrient inputs and pest-control products, but some of the benefits that we'll be measuring will be long-term," she says.

With financial incentives since 2002, the practice has spread briskly, says Jennifer Miller of Northwest Coalition for Alternatives to Pesticides. And so have the questions that farmers have been asking about how best to grow them.

"We want to make sure the practices are healthier for water, soils and air and for Idaho's human life and wildlife," Miller says. "But we also understand that these solutions have to be economically viable for farmers."

The project plans to host a public field day in mid-October.