Jeff and Pam Riesgraf — who manage a certified organic dairy and crop operation near Jordan, Minnesota — began composting manure from their dairy herd in 1993. They had two major objectives. First, they wanted to reduce weed seeds naturally present in manure. At the same time, they understood the need to protect water quality by reducing runoff caused by freshly spread raw manure. What the Riesgrafs hadn’t anticipated when making the switch to manure composting was a more than 30 percent reduction in annual fuel and labor operating costs.
These statistics on the Riesgraf farm were compiled by economic consultant Gigi DiGiacomo as part of the Sustainable Farming Systems Project and reviewed by staff at the Land Stewardship Project, University of Minnesota Manure Research Program, the Sustainable Farming Association of Minnesota, and the Minnesota Institute for Sustainable Agriculture. Researchers at the University of Minnesota’s Department of Soil, Water and Climate monitored water quality.
FROM SCRAPING AND SPREADING TO SCRAPING AND WINDROWING
Annual fuel and labor operating costs total $1,873.90 under the Riesgraf composting system — less than two-thirds the cost associated with raw manure management despite the added step of compost turning eight times per summer. Reduced fuel and labor expenses under the composting system are the result of manure volume shrinkage and hence fewer loads of manure to handle and spread and reduced field cultivation owing to decreased weed populations.
Prior to 1993, Jeff scraped and hauled the equivalent of 27,000 bushels of manure produced by his dairy herd each year to crop fields (located within one mile from the farmstead), where it was spread in spring and fall. Under the composting system, he hauls the same amount of raw manure a short distance to a well-drained site approximately 100 yards from the farmstead, where it is piled for composting. After one year of composting, the manure pile shrinks approximately 65 percent in volume, under their farm conditions. Consequently, the Riesgrafs’ annual manure volume totals approximately 8,800 bushels after composting. This means fewer loads of manure to haul from the compost pile to fields for spreading, saving 47 hours of labor and 78 gallons of fuel.
Until he began composting, Jeff used to rotary hoe and cultivate his organic crop fields four to five times each growing season to control weeds. Heat generated during composting kills many of the weed seeds. As a result of reduced weed populations in the composted manure, Jeff can now control weed populations with three to four passes across his fields each growing season, compared to four to five passes under the raw manure system. In this process, he is able to cut fuel use by 45 gallons and labor time by 30 hours.
Annual fuel and labor savings are offset by added composting equipment costs under the composting system. In addition to the Bobcat and manure spreader they already own, the switch to manure composting required the purchase of a compost turner. In 1993, they purchased a Wildcat turner with another farm family. The Riesgrafs’ share of the investment was $7,500, which they financed with a low-interest loan (six percent interest over seven years) from the Minnesota Department of Agriculture’s Sustainable Agriculture Loan Program. Once new equipment costs are factored in, annual direct manure management expenses on the Riesgraf farm total $2,803.90 under the composting system compared with $2,857.80 under the raw manure system. Table 1 compares the annual direct expenses associated with manure management and field cultivation under the composting system in 1999 and under the raw or solid manure system prior to 1993. Direct operating expenses are broken out by fuel and labor operating expenses.
OTHER DIRECT AND INDIRECT BENEFITS
In addition to reduced annual operating expenses, the Riesgrafs have observed other direct and indirect management benefits associated with manure composting on their farm. According to Jeff, the “biggest benefit” is improved weed control and less soil compaction because of a reduction in cultivation. “We’ve noticed a change in both weed populations and the number of weeds,” Jeff says. With fewer weeds to cultivate, Jeff has reduced the number of passes across his fields and consequently lowered soil compaction.
Composted manure is also easier to spread. “Because it is dryer, the compost spreads more uniformly than raw manure,” he points out. Composted manure also offers more plowing flexibility when compared with raw or fresh manure. Prior to composting, Jeff applied 90 percent of his raw manure to fields prior to the growing season and had to wait several days after spreading before he could begin plowing because it was generally too wet. Conversely, composted manure can be turned into the soil one day after spreading. Last, but not least, observes Pam, is the reduction in manure odor. Around the farmstead and near the fields, Jeff and Pam have noticed a big difference. Composted manure emits little or no odor when stacked or spread as compared to wet, raw manure.
For more information about the far-reaching scope of the Sustainable Farming Systems Project, contact Caroline van Schaik, Land Stewardship Project, White Bear Lake, MN 55110, (651) 653-0618, e-mail: firstname.lastname@example.org; Helene Murray, Minnesota Institute for Sustainable Agriculture (612) 625-8235; John Lamb, The Minnesota Project, St. Paul, MN (651) 645-6159, e-mail: email@example.com; Gigi DiGiacomo, Economic Monitoring Research, (612) 545-8634, e-mail: firstname.lastname@example.org.