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Livestock and poultry manure can provide valuable organic material and nutrients for crop and pasture growth. However, nutrients contained in animal manure can degrade water quality if they are overapplied to land and enter water resources through runoff or leaching. The nutrients of greatest water quality concern are nitrogen and phosphorus. Animal waste is a source of both.
A shift in the livestock and poultry industry over the past several decades toward fewer, larger operations has prompted public concern over the use and disposal of animal manure.
Producing feed on the farm, once a mainstay of animal production, is becoming rare. As animal operations grow larger, they increasingly buy feed from outside the farm. This is reflected in the reduced amount of available cropland per animal on livestock and poultry farms (Gollehon et al., 2001). Nevertheless, land application is still the predominant method for disposing of manure and recycling its nutrient and organic content . Concerns have consequently arisen that crops and other vegetation are not fully assimision affecting the potential for contamination of water resources by manure nutrients (Mulla et al., 1999).
Recent policies and programs for increasing the efficient use of nutrients and protecting water quality from nutrient runoff all emphasize the importance of properly handling animal manure. Land application is the most common, and usually most desirable method of utilizing manure because of the value of the nutrients and organic matter. Land application should be planned to ensure that the proper amounts of all nutrients are applied in a way that does not cause harm to the environment or to public health. Land application in accordance with a comprehensive nutrient management plan (CNMP) should minimize water quality and public health risk . A goal is that all animal feeding operations regardless of size voluntarily adopt for managing their nutrient resources, including both commercial fertilizer and animal manure.