Changes in Available P and Extractable Metals in Soils Amended With Separated Liquids and Separated Solids From Swine Slurry.

Solid-liquid separation is a manure management option for swine slurry whereby N-rich liquid is separated from P-rich solid, allowing the separated liquid to be used as an N source to crops without over-supplying P. There is not much information on how amending soil with separated solids and liquids of swine slurry would influence soil available P and extractable metal concentrations. This study evaluated the changes in available P, and extractable metals in soils after amending with raw manure and their separated liquid and solids from three techniques of solid-liquid separation; centrifuging without a flocculant, centrifuging with a flocculant and rotary press with a flocculant. An incubation study was conducted using two soils, Newdale series and Denham series with nine manure-amended treatments, a monoammonium phosphate amended treatment and an un-amended treatment. Manure treatments included raw manure slurries and their solid and liquid separates for each separation technique. For amended treatments manure or fertilizer were added at a rate equivalent to 100 kg of P ha^-1. Soils were mixed, moistened to field capacity and incubated for 16 weeks. Soil samples were periodically taken and analyzed for Olsen P and DTPA extractable Cu, Zn, Se, Ni and Pb. Olsen P was significantly greater in manure or fertilizer amended soils than in un-amended soils throughout the incubation period. Amendment with the liquid separated by rotary press with a flocculant gave the greatest Olsen P concentration during most sampling periods. Increase in DTPA extractable Se, Ni, Pb, and Cu concentrations were significantly greater in soils treated with liquid separates compared to their corresponding solid separates. However, the increase in DTPA extractable Zn was significantly less with liquid separates than with their corresponding solid separates or raw manure. The results therefore, did not always conform to the expectation that amendment with separated liquid of swine slurry would have less influence on soil available P and metal concentrations than its solid separate.