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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Summer 1999 Summary: There is no question that the application of animal manure to cropland will continue to have an impact on N, P and K use in the future, but certainly at a much lower percentage than the potential calculated by the Council for Agricultural Science and Technology (CAST). As yields increase and demand for fertilizer nutrients goes up, part of the impact will be absorbed or minimized. However the fact remains that animals produce a lot of waste that must be disposed of in some manner. Such disposal will be a factor in the fertilizer market in the days to come. You may or may not have read a report issued out of the minority staff of the Senate Committee on Agriculture in late 1997 expressing a growing concern for environmental risks associated with livestock production in the U.S. Senator Tom Harkin (D) of Iowa was quoted at the time as saying, "The impact of pollution is no longer confined to only a few rural areas." Some of the unsettling statistics in the report included: • In 60 percent of rivers and streams that the EPA has identified as impaired, agricultural runoff, including nutrients in animal waste, is the largest contributor to pollution. • Broiler litter from a typical broiler house (22,000 birds) contains as much P as is in the sewage from a community of 6,000 people. • On the Delmarva Peninsula, 600 million chickens produce over 3.2 billion pounds of raw waste per year, asmuchNasacityofnearlyahalf million people. While the above statements have no direct relationship to the replacement value of animal manure for commercial fertilizers, they do reflect a growing concern over the negative effects of animal wastes on the environment and even human health. For example, the outbreak of Pfiesteria piscicida, which killed nearly a half million fish in North Carolina and the Chesapeake Bay in 1997, has been associated with but by Drs. B.C. Darst and P.E. Fixen What About Manure? Plenty of controversy swirls about risks, availability, current use, and potential use of manure with commercial fertilizers. never linked to the use of animal wastes. The fear factor, however, helped to speed new legislation and regulations. Manure as substitute An important question then becomes: how much commercial fertilizer (NPK) will (can) animal manure replace? A CAST report estimated that up to 29 percent of N, and 68 percent of each P2O5 and K2O in commercial fertilizers could potentially be replaced by manure, noting at the same time that amounts of commercial fertilizers replaceable by animal manure vary widely by U.S. region. Others have calculated figures similar to those in the CAST report. Figure 1. Nutrient status of manure from North Carolina livestock at different stages after collection, 1993. Fresh Manure Status 15 30 45 60 75 90 105 % of Nutrient Available N PO 25 KO 2 Collectible After storage At field
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