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About two-thirds of the beef cattle feeding in the United States occurs in Nebraska, Texas, Kansas, Iowa, and Colorado. Over 80 percent of the fed cattle are produced in feedlots of over 1,000 head capacity. Manure produced by fed cattle, if all were conserved and utilized, would provide 100 kg nitrogen (N) ha sup -1 (89 lb N a sup -1 ) for 8.4 percent of the corn and wheat acreage in the nation. Nutrients excreted in beef feedlots would cost over $461 million if purchased as fertilizer. However, under present practices, about 50 percent of this N is lost (primarily by runoff, ammonia volatilization, and denitrification) before removal from the feedlot. In addition, 50 percent of the remaining N may be lost in hauling, spreading, and incorporating manure into the soil.
Phosphorus (P) losses are less, because P is lost primarily through runoff. Because beef feeding is concentrated where a high percentage of the land is cultivated, there is usually ample land area within economically acceptable distance on which to use manure. However, acceptable soil loading rates have not been well defined, because of variability in manure composition, unpredictable mineralization rates, and lack of loading rate standards. Should rates be based on N or on P buildup in soils?
Basic soil microbiological studies on manure decomposition are needed to predict the fate of nutrients in manure when land applied. In the beef fattening area, there is at present only limited opportunity for using manure for purposes other than land application. Besides problems of nutrient conservation in feedlots (feedlot management problems) and in transporting and land application, problems also exist in using manure with no-tillage systems to achieve conservation compliance for soil erosion control, environmental problems associated with composting, pollution from abandoned feedlots, salt buildup, ground water contamination and others. An educational program is also needed to achieve the required technology transfer for efficient nutrient conservation and control of environmental degradation.
Introduction
When animals graze on pasture and rangeland, manure is dispersed across a large area and little management is needed because the material is not concentrated and decomposes on the soil. However, when animals are concentrated in a small area, like a feedlot, the quantity of manure needing management increases significantly. In the United...