Turning Schedules Influence Final Compostion of Composted Swine Manure.

Liquid swine (Sus scrofa domesticus) manure is a high-moisture, low-nutrient product that limits economical transport to areas in proximity of its source, possibly contributing to localized high soil nutrient levels. Composting swine manure converts liquid slurries to solids at lower moisture content, reduces the volume and weight of material, and the stabilized product is more easily transported off-site. This study examined if compost management influenced properties of semi-composted swine manure-woodchip mixtures from high-rise finishing facilities. The effects of composting in fall (FT) or spring (ST) were examined for treatments turned once (1X) or three times (3X) per week, upon reaching 65 °C (65C), or not turned (NT) at USDA-ARS facilities in Bowling Green, Kentucky. Treatments were turned using a tractor powered windrow compost turner. All turned compost treatments reached and maintained thermophilic composting temperatures (>50 °C), but occurred within 4 d in all piles for FT and between 31 d and 80 d for ST. Composting ceased in 112 days for FT when compost temperatures stabilized at ambient temperatures. Composting ceased in 143 days for ST when the 3X pile reached ambient temperatures. Compost volume was reduced by 50% to 60% for all turned piles. Carbon, NH₄-N, K, Na, and S decreased while C/N ratio, NO₃-N, P, Al, and Zn increased for all turned FT compost treatments. In all FT compost treatments, C and NH₄-N decreased, while C/N ratio, NO₃-N, K, Al, Ca, and S increased for all turned FT compost treatments. Final NO₃-N levels exceeded NH₄-N levels for all treatments except FT 65C. Less frequent turning tended to promote greater nutrient conservation while still allowing for adequate volume reduction.