Using Rare Earth Elements to Control Phosphorus and Track Manure in Runoff

Concern over the enrichment of agricultural runoff with phosphors (P) from land applied livestock manures has prompted the development of manure amendments that minimize P solubility in this study, we amended poultry, dairy, and swine manures with two rare earth chlorides, lanthanum chloride (LaCl3 7H(2)O) and ytterbium chloride (YbCl3 center dot 6H(2)O), to evaluate their effects on P solubility in the manure following incubation in the laboratory as well as on the fare of P and rare earth elements (REEs) when manures were surface-applied to packed soil boxes and subjected to simulated rainfall. In terms of manure P solubility, La.water-extractable P (WED) ratios close to 11 resulted in maximum WEP reduction of 95% in dairy manure and 98% in dry poultry later. Results from the runoff study showed that REE applications to dry manures such as poultry litter were less effective in reducing dissolved reactive phosphorus (DRP) in runoff than in liquid manures and slurries, which was likely due to mixing limitations The most effective reductions of DRP in runoff by REEs were observed in the alkaline pH soil, although reductions of DRP in runoff from the acidic soil were still >50% Particulate REEs were strongly associated with particulate P in runoff, suggesting a potentially useful role in tracking the fate of P and other manure constituents from manure-amended soils Finally, REEs that remained in sod following runoff had a tendency to precipitate WEE especially in sods receiving manure amendments. The findings have valuable applications in water quality protection and the evaluation of P site assessment indices