Increases in the demand for poultry products have led to rapid and concentrated growth of the industry, which has caused excessive manure supplies in certain areas. Although poultry litter is one of the best organic fertilizers available, and is an extremely valuable resource, excessive land application rates can lead to nitrate leaching into groundwater, phosphorus (P) runoff into adjacent water bodies, and possibly cause elevated bacterial or viral pathogen levels in lakes and rivers. Approximately 13 million Mg (14 million tons) of litter and manure was produced on U.S. poultry farms in 1990, most of which (68%) was broiler litter. Except for small amounts used in animal feed, the major portion (>90%) of poultry litter produced is applied to agricultural land. Adverse impacts resulting from land application of poultry manure may be prevented by implementation of effective best management practices (BMPs). Examples of BMPs include proper nutrient management using agronomic rates of N and/or P, use of buffer zones between treated areas and waterways, correct timing and placement of manure, and irrigation scheduling of liquid manure to limit groundwater contamination. Nutrient loading rates should be based on P in areas of the country that have P sensitive waterbodies and on N in areas where eutrophication of surface water is not a problem. These practices manipulate the soil system to minimize pollutant loss to surface or groundwater. Future research needs include the development of new BMPs that result in decreased negative environmental impact from land applications of this important resource.
P.A. Moore Jr. is with the U.S. Department of Agriculture—Agricultural Research Service and T. C. Daniel is with the Agronomy Department, University of Arkansas, Fayetteville 72701; A.N. Sharpley is with USDA—ARS, National Agricultural Water Quality Laboratory, Durant, Oklahoma 74702; and C. W. Wood is with the Agronomy and Soils Department, Auburn University, Auburn, Alabama 36849.