Reducing labile phosphorus in liquid swine manure with chemical amendments and storage time

Manure application in agriculture risks phosphorus (P) runoff. This incubation study evaluated the effect of manure treatments with alum, gypsum, and Epsom salt (300 mg L-1) prior to soil application in reducing labile phosphorus in swine manure and manured soils. The manure treated with alum had significantly lower water-extractable P (20% and 36% decrease) than the Epsom salt-treated and untreated manure after 7-day incubation. However, when the treated manure was applied to soils, there was no significant difference in water-extractable P or Olsen P compared with untreated manure. Increased amendment rates and multiple applications can be explored in future research.