The Wisconsin Manure Irrigation Workgroup, a UW-Madison/UW-Extension-led group tasked with assessing the potential advantages and concerns associated with manure irrigation, released its final report today (April 14) following a webinar presentation about the report’s findings. The 80-plus-page report document, titled “Considerations for the Use of Manure Irrigation Practices,” is now available online at http://fyi.uwex.edu/manureirrigation/. A recording of today’s webinar and other relevant materials are also posted on the website.
Manure irrigation is the practice of applying livestock manure to fields using irrigation equipment. Although not currently in wide-spread use in Wisconsin, the practice is expected to grow over time. At the same time, there is increasing debate about the pros and cons of this practice. Many communities are struggling to make decisions about if and how manure irrigation can work for them—often due to a lack of information.
To help address this information deficit, in 2013, the Wisconsin Department of Agriculture, Trade and Consumer Protection and the Wisconsin Department of Natural Resources requested UW-Madison/UW-Extension convene a workgroup to study the issue. The workgroup, composed of scientists, public health specialists, state agency experts, farmers, conservationists and others, spent over two years gathering and reviewing scientific information on the practice and developing their report, which includes findings, responses and recommendations.
Recognizing that any future public policy would originate at the state and local levels, the group aimed to gather critical information and put it in the hands of the people who need it most. “Our mission was to review the information available and compile it into a document to help citizens and local governments decide their futures,” says workgroup chair and report co-editor Ken Genskow, UW-Madison associate professor of urban and regional planning and UW-Extension water resources planning specialist.
Early on, the workgroup gathered citizen input to help guide its efforts, hosting public symposia on the topic—which included opportunities for public comment—in Stevens Point and Menasha. Workgroup meetings were open to the public, and workgroup members accepted comments throughout the process.
“The input helped set the agenda for our group discussions,” says Genskow.
The workgroup assessed concerns associated with manure irrigation, including droplet drift, odor, water quality, air quality and airborne pathogens. They also explored potential benefits related to the timing of manure applications, road safety and reduced road damage, and other farm management and economic benefits.
To understand the human health risks associated with manure irrigation, researchers need to understand how long pathogens survive after being sprayed into the air. A lack of field studies of the practice led the USDA Agricultural Research Service to conduct a study in tandem with—but independently from—the workgroup’s efforts. The results of that project are shared at the end of the report, in a section titled “Airborne Pathogens from Dairy Manure Aerial Irrigation and the Human Health Risk.”
“This USDA-ARS study was the first in-the-field research project to measure pathogens and other microbes being spread through the air in this way and to then calculate a risk. The research found that risk of acute gastrointestinal illness from pathogens reduces with increased distance,” explains workgroup member and report co-editor Becky Larson, UW-Madison assistant professor of biological systems engineering and UW-Extension biological waste specialist.
The final chapter of the report includes responses to potential benefits and concerns, and, taking all of these factors into consideration, it offers science-based recommendations for reducing risks from manure irrigation.
“We really want to reach local officials and others interested in the issue, so they are aware of this resource and they know where to look for more information,” says Genskow.
In order to give people a chance to read and discuss the full 80-plus-page report and then ask questions, a follow-up webinar will be held during the week of May 16. Details will be shared in a future media advisory.