Nutrient imbalances present problems in urban fringe watersheds, with an oversupply of local organic nutrients in some areas of the watersheds. Use of organic materials from livestock farms and recycled urban waste streams can help improve soil productivity and reduce nutrient imbalances, and can contribute to the sustainability of local agriculture. A number of barriers exist to more widespread and efficient use of local organic materials in agriculture. These include concerns about availability of supplies relative to application timing, consistency of materials, compatibility with equipment and farming practices, economic questions, and potential side effects such as weeds, pathogens, and odors. A key issue is the need for better information on nutrient availability. In 2004 we completed a 3-year field and laboratory research project studying nitrogen availability from a range of composted and uncomposted local organic amendments. Research was done at WSU and OSU. Results of this research are used for guidance for organic nutrient management in the Northwest.
Organic fertilizer calculator worksheet: ♣ Downloadable worksheet for calculating organic fertilizer rates, developed at Oregon State University using the results of this research and subsequent laboratory research by Dan Sullivan at OSU.
Estimating plant available nitrogen release from manures, composts, and specialty products. Gale, E.S., D.M. Sullivan, C.G. Cogger, A.I. Bary, D.D. Hemphill, and E.A. Myhre. 2006. J. Environ. Qual. 35:2321-2332. (♣ Request pdf e-copy)
Predicting plant-available nitrogen from organic amendment in the second year after application. Kusonwiriyawong, C., D.M. Sullivan, D.D. Hemphill, C.G. Cogger, A.I. Bary and E. Myhre. 2014. Acta Hort. 1018: 325-333. (♣ PDF-Online)