Water-related issues in sustainability: nitrogen and phosphorus management

Water quality in the USA and around the world is threatened by contamination with nutrients, primarily nitrogen (N) and phosphorus (P). Animal manure can be a valuable resource for farmers, providing nutrients, improving soil structure and increasing vegetative cover to reduce erosion potential. At the same time, application of manure nutrients in excess of crop requirements can result in environmental contamination. Concentrated animal agriculture has been identified as a significant source of nutrient contamination of surface water, N contamination of groundwater and ammonia emission. Areas facing the dilemma of an economically important livestock industry concentrated in an environmentally sensitive area have few options. If agricultural practices continue as they have in the past, despite the significant changes in agricultural intensity and changing environmental conditions, continued damage to water resources and a loss of fishing and recreational activity are inevitable. If agricultural productivity is reduced, however, the maintenance of a stable farm economy, a viable rural economy and a reliable domestic food supply are seriously threatened. This chapter reviews impacts of nutrient pollution on ground and surface water, issues of nutrient imbalance related to animal agriculture in developing and developed countries, and impacts of more stringent regulations on water quality