Turning Schedules Effect Nutrient Content of Composted Swine Manure.

Concentrated animal feeding operations (CAFOs) generate large amounts of manure per area basis.  This manure must be removed and disposed of or utilized in an environmentally sound manner.  Land application to crop land is the most common method of waste disposal.  For much of the year, land application is not possible due to cropping cycles and alternatives are necessary.  One alternative is to compost animal manure during the growing season to produce a stable product that can be stored on-farm until land application is feasible, while reducing the volume.  An experiment was designed to determine the optimal turning frequency of swine manure with wood chip based bedding material to produce a “finished” compost.  The experiment consisted of three treatments that were turned once weekly, three times weekly, or when the temperature reached 150 F.  These piles were compared to the same material that was piled and not disturbed during the same time frame.  The pH of the compost remained relatively stable between pH 7.4 to 7.7 throughout the timeframe of the composting. Nutrient values changed over time, with the biggest change occurring with N.  Both NH₄-N and NO₃-N decreased over time with all managed treatments.  However the static pile has greater NH₄-N than any other treatment.  Total N increased over time, likely due to increased microbial biomass and activity and concomitantly immobilizing available N.  Potassium was lower in the static pile compared to the managed piles regardless of turning frequency; however P values did not differ.  Temperatures stabilized near 65° F for all treatments when the composting was deemed complete.  At this time the absolute reduction in volume has not be quantified, but a substantial volume reduction was observed.  By producing a stable product of reduced volume, composting swine manure during the growing season is a viable option to land application.