Spring 2001
Survey shows manure sampling yields positive results
by Tracy S. Petersen, freelance associate
Livestock
producers in Sioux County do a better job of managing manure as a nutrient
than their counterparts statewide, according to an Iowa State University
Extension survey. Sioux County is Iowa’s largest livestock-producing
county.
Joel DeJong, extension field crops specialist in northwestern Iowa, pointed to economics as the reason for the county’s positive survey results. “Those who take credit for their manure have a smaller cash outlay for commercial fertilizer,” DeJong said. “Plus, the farmers recognize the risks and social concerns about managing manure improperly.”
DeJong and Kris Kohl, extension agricultural engineer in northwestern Iowa, received funding from ISU’s Leopold Center for Sustainable Agriculture to conduct the survey early last year. They did so after learning that an Iowa Farm and Rural Life poll indicated only 47 percent of Iowa farmers were taking credit for their manure applications. The survey conducted by DeJong and Kohl indicated that 95 percent of Sioux County livestock producers reduced their use of commercial fertilizer. “Those who have a laboratory to analyze their manure take more credit for its fertilizer value, because they know what they’re applying,” DeJong said. “So now we’re emphasizing sampling.”
To inform livestock producers of the benefits of sampling, extension specialists in the area use newsletters, speak at manure applicator certification meetings, and work one-on-one with producers. The response has been positive. “People are unsure about the management of manure, so they’re looking for information,” DeJong said.
Once they better understand how to predict the nutrient value of manure, producers’ biggest investments are in testing, time, and management. “Most have the equipment, but need to spend some time and energy calibrating it,” DeJong said. “A lot of older equipment can do a decent job.” DeJong added, “We need to evaluate the equipment and manure as a nutrient form, so we manage it as a nutrient and not a waste. That means paying attention to all the details. We should be weighing the tanks to be sure we’re getting the gallons applied per acre that we plan for. And we need to know, not guess, the nutrient value of the manure applied. For example, we’ve seen nitrogen levels in swine finishing units ranging from 35 pounds per thousand gallons to 85 pounds per thousand gallons.”
Most producers who actively manage their manure find the effort is worthwhile. Of the 51 percent of the survey respondents who do test their manure, 36 percent said they apply no additional nitrogen to their fields. Sixty-eight percent apply no additional phosphate, 69 percent apply no additional potash, and 51 percent apply no additional commercial micronutrients. In comparison, of those who do not test their manure, only 15 percent said they apply no additional nitrogen, 38 percent apply no additional phosphate, 37 percent apply no additional potash, and 30 percent apply no additional commercial micronutrients. Furthermore, most producers who have their manure analyzed feel their crops yield somewhat better. DeJong said that’s not always the case, although studies do indicate that manure applications do sometimes improve yields.
For more information about manure management or a list of laboratories that conduct manure analysis, contact your local county extension office or visit the Iowa Manure Management Action Group Web site at http://extension.agron.iastate.edu/immag/
