Poultry manure and spent bedding material or litter has been used for crop fertilizer based on its nitrogen value. The phosphorus content of the manure is roughly 1/3 −1/2 the numeric value of the nitrogen value. That is 26–73 lb N/ton and 7–37 lb P/ton
for Broiler and caged layer manures and litter. (1). Crop needs for nitrogen are in several fold excess of P requirements. The soil can be come saturated with P being classified as eutrophic at > 75 mg P/kg soil (2). The P binding capacity of the soil is dependent upon many factors
including iron, aluminum and calcium concentrations; pH; oxygen levels; other ligands and moisture. The P in excess of crop requirements and not bound in soil can enter surface and subsurface waters through runoff and percolation. This P, either inorganic like dicalcium phosphate or organically
bound, is largely soluble and immediately available as an alga nutrient. A large input of P to surface waters is erosion of the P laden soil. The receiving water chemistry will have an impact on the rate and mechanisms of the release of P from the soil particles and the more loosely sorbed
P will be released as bio-available P. The results have been well-publicized degradation of surface water supplies, fisheries and alleged toxic algae blooms (3).
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