Animal management to reduce phosphorus losses to the environment1

Abstract

Water quality in the United States is threatened by contamination with nutrients, primarily nitrogen and phosphorus. Animal manure can be a valuable resource for farmers, providing nutrients, improving soil structure, and increasing vegetative cover to decrease erosion potential. At the same time, application of manure nutrients in excess of crop requirements can result in environmental contamination. Environmental concerns with P are primarily associated with pollution of surface water (streams, lakes, rivers). This pollution may be caused by runoff of P when application to land is in excess of crop requirements. Increased specialization and concentration of livestock and crop production has led to the net export of nutrients from major crop-producing areas of the country to areas with a high concentration of animal agriculture. Concentrated animal agriculture has been identified as a significant source of P contamination of surface water. 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, continued damage to water resources and a loss of fishing and recreational activity are inevitable. If agricultural productivity is decreased, however, the maintenance of a stable farm economy, a viable rural economy, and a reliable domestic food supply are seriously threatened. Decreasing the P content of manure through nutrition is a powerful, cost-effective approach to reducing P losses from livestock farms and will help farmers meet increasingly stringent environmental regulations. This paper reviews opportunities available to reduce the P content of livestock manure, including more accurate interpretation of the published P requirements of animals, improved diet formulation and group-feeding strategies to more precisely meet requirements, and approaches to improve availability of feed P for monogastric and ruminant species.

The environmental impact of recombinant bovine somatotropin (rbST) use in dairy production

“…20) intake is captured in milk, with the remainder excreted via feces and urine. Dairy manures therefore contain appreciable quantities of N and P in a ratio that is inefficient in meeting crop nutrient needs (20). Applying sufficient manure to fulfill N requirements (as is often practiced), may saturate the soil's P-holding capacity, allowing excess P to transfer into water courses via surface runoff and increasing the potential for eutrophication to occur.…”

Methods for assessing phosphorus overfeeding on organic and conventional dairy farms

“…However in Europe and the United States, where deficiency is unusual, the current emphasis is on diminishing P from dairy operations because P overloading can be harmful to the environment (Nennich and Harrison, 2008). Many studies have shown that dairy cows are often fed more P than they require according to current recommendations (Wu et al, 2001;Valk et al, 2002;Knowlton et al, 2004;Nennich and Harrison, 2008). Manure from dairy cows fed high levels of P has been shown to increase the potential for P runoff losses (Ebeling et al, 2002).…”

Impact of nutrition on nitrogen, phosphorus, Cu and Zn in pig manure, and on emissions of ammonia and odours

“…Totally, 70% of P ingested is excreted either via the faeces or via urine. In order to reduce P losses, P supplied to pigs should be adjusted to their requirement, and strategies to improve P availability should be implemented (Poulsen, 2000;Knowlton et al, 2004). This approach relies on an accurate knowledge about feed P availability and P requirement according to the physiological status of pigs.…”