As my part of the Philomath High School Compost Research Project, I studied the changes in forms of nitrogen in a compost pile as it matured. I analyzed the levels of ammonium and nitrate in leachate prepared from samples collected bi-weekly from a windrow managed by a local commercial composting business, Soil Smith Services. The compost was composed of cow and chicken manures as well as leaf litter. I conducted my analyses with Dr. David Myrold, Professor of Soil Sciences at Oregon State University, a community mentor. We used a diffusion method to isolate the ammonium and nitrate from the compost leachate. The concentrations of these molecules, in parts per million nitrogen, were then measured using a colorimeter. Figure 1 shows the concentrations of ammonium and nitrate in the leachate prepared from four samples during composting weeks 6, 8, 10 and 12.
Figure 2 shows that there is an almost complete conversion of ammonium to nitrate in the compost pile. While composting is a viable method for dealing with manure, it still possesses the potential for environmental harm. Nitrate can lead to cultural eutrophication, so it is necessary to use safe practices when composting and when applying compost products.
Dr. David Myrold
Dr. Clare Reimers
Benton County Department of Environmental Health
Mrs. Molly O’Malley
Mr. Jeff Mitchell
Mr. Tom Thompson