PHS Compost Project: Nitrogen Levels in Manure

Brian Wakefield

Brian Wakefield demonstrates the mix-and-quarter technique used for sample preparation.
Brian Wakefield's lessons learned: Perseverance, Patience, and Don't Always Trust the Method.
Brian Wakefield demonstrates the mix-and-quarter technique used for sample preparation.
Agricultural production of manure presents a serious threat to the environment. The forms of nitrogen present in manure can lead to eutrophication and other environmental problems (fish poisoning) if allowed to leach into the surrounding environment. Composting provides one successful method of buffering the immediate danger of agricultural manure by converting organic nitrogen in animal waste to ammonium and nitrate, nitrogen forms used by plants.

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.

Figure 1: Ammonium and Nitrate Concentrations in Compost Leachate Samples
Figure 1: Ammonium and Nitrate Concentrations in Compost Leachate Samples
Figure 2: Ammonium Nitrate as a Function of Composting Time
Figure 2: Ammonium Nitrate as a Function of Composting Time

Presentation

Acknowledgments

Dr. David Myrold
Dr. Clare Reimers
Teresa Matteson
Benton County Department of Environmental Health
Mrs. Molly O’Malley
Mr. Jeff Mitchell
Mr. Tom Thompson