Excessive loading of phosphorus (P) onto agricultural lands has been recognized as a surface water quality threat in both Europe and the United States. Methods that can reduce either P input to the environment or P movement into surface waters are needed to address this problem. Binding soluble phosphorus (SP) with aluminum to form aluminum phosphate in swine slurries can reduce the movement of P into surface waters. In the form of aluminum phosphate, phosphorus is not available to the environment. It can only become available if a large shift in pH occurs. Reducing the movement of P in slurries enables producers to land apply manure with a reduced risk of pollution.

Two field experiments were conducted to assess the practicality of reducing soluble phosphorus in swine waste slurry through the addition of aluminum chloride (AlCl₃), under field conditions. One of the swine slurry holding ponds tested initially had low SP concentrations, 22.5 mg L-1; the other initially had high SP concentrations, 354 mg L-1. The second holding pond was twice the size of the first, yet both ponds were treated with equal amounts of AlCl₃.

Results show a 79% reduction from the low SP containing holding pond and only a 20% reduction in the high SP containing holding pond. However, the AlCl₃ was much more efficient at reducing SP from the high SP slurry than the low SP slurry, 48% efficiency vs. 6%.

Field scale control of SP using chemical amendments such as AlCl₃ is technically feasible, especially in slurries with a high SP content.