Evaluation of Amendments to Control Phosphorus Losses in Runoff from Pig Slurry Applications to Land

If spread in excess of crop requirements, incidental phosphorus (P) losses from agriculture can lead to eutrophication of receiving waters. The use of amendments in targeted areas may help reduce the possibility of surface runoff of nutrients. The aim of this study was to identify amendments which may be effective in reducing incidental dissolved reactive phosphorus (DRP) losses in surface runoff from land applied pig slurry. For this purpose, the DRP losses under simulated conditions across the surface of intact grassland soil cores, loaded with unamended and amended slurry at a rate equivalent to 19 kg Pha(-1), were determined over a 30h period. The effectiveness of the amendments at reducing DRP in overlying water were (in decreasing order): alum (86%), flue gas desulfurization by-product (FGD) (74%), poly-aluminum (Al) chloride (PAC) (73%), ferric chloride (71%), fly ash (58%), and lime (54%). FGD was the most costly of all the treatments (7.64 pound/m3 for 74% removal). Ranked in terms of feasibility, which takes into account effectiveness, cost, and other potential impediments to use, they were: alum, ferric chloride, PAC, fly ash, lime, and FGD.