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Challenges and opportunities facing animal agriculture: Optimizing nitrogen management in the atmosphere and biosphere of the Earth¹

E. B. Cowling^*,2 and J. N. Galloway

^* North Carolina State University, Raleigh 27695 University of Virginia, Charlottesville 22904

² Correspondence: 1509 Varsity Drive, Raleigh, NC 27606 (phone: 919-515-7564; fax: 919-515-1700; E-mail: ellis_cowling{at}ncsu.edu).

Abstract

Humans need food. Humans use energy. Production of food and combustion of fossil fuels increase concentrations of reactive nitrogen in the atmosphere, soils, and surface and ground waters of the Earth. These increases are caused in part by agricultural practices aimed primarily at increasing food production: the use of synthetic nitrogen fertilizers, widespread planting of N-fixing legumes, increased demand for animal protein in human diets, and increased use of fossil fuels. The world's crops, forests, and fisheries respond to reactive nitrogen (defined in the body of this article) enrichment with some positive benefits (such as increased food, feed, timber, and fish production) and some negative consequences (including acidification and eutrophication of aquatic and terrestrial ecosystems, decreased biodiversity, increased regional haze, global warming, and such human health impacts as nitrate contamination of drinking water and increased pulmonary and cardiac disease caused by exposure to toxic ozone and fine particulate matter).

So far, most pollution abatement strategies have aimed at resolving one or another air or water pollution problem in which various oxidized, reduced, and organic forms of reactive nitrogen play an important part. The time has come to consider more fully integrated strategies by which reactive nitrogen management practices can be optimized to increase agricultural, forest, and fish production while decreasing nitrogen-induced soil, air, and water pollution.

Contemporary challenges and opportunities facing animal agriculture in the United States today include joining with the U.S. Environmental Protection Agency, animal industry, university, and other scientists and policy makers in making realistic assessments of actual positive and negative impacts of reactive nitrogen emissions and leaching from animal agriculture and developing practical (economic) guidelines and strategies for the following: a) improving nitrogen conversion efficiency in poultry, swine, beef/dairy, and fish production, b) minimizing reactive nitrogen losses from manures, c) conserving and reusing reactive nitrogen and other valuable nutrients in animal wastes, d) developing more cost-effective horizontally and vertically integrated systems of animal production and manure management through production and marketing of value-added products, and e) minimizing use of fossil fuels in agriculture.

¹ The authors are indebted to Viney Aneja, Lee Allen, Anita Bahe, Leonard Bull, Kathy Cochran, Jan Willem Erisman, Cari Furiness, Barbara Glenn, Walter Heck, Sheila Holman, Steve Levitas, Robert Mikkelsen, George Murray, Brock Nicholson, Wayne Robarge, Joseph Rudek, Jason Shih, Stan Smeulders, Henry Tyrrell, and Mike Williams for their help in developing some of the ideas in this paper.