Effects of turning frequency on composting of spent pig-manure sawdust litter

Spent pig-manure sawdust litter (spent litter) disposed of from the pig-on-litter (POL) system was collected to investigate the effects of turning frequency on composting. Three heaps of the spent litter were piled up coinciding with the three turning frequency treatments: Pile A = turned every 2 days; Pile B = turned every 4 days; Pile C = turned every 7 days. Turning frequency appeared to affect a number of important composting parameters; temperature, pH, NH⁺₄-N, humic acid and ATP content, and germination index. On the whole, piles A and B had a faster rate of composting and took a shorter time (two months) to reach maturity than did pile C. The phytotoxicity in piles A and B was also eliminated more efficiently than in pile C. These results suggest that turning every 2 or 4 days is the more suitable turning frequency for composting of spent litter. At this turning frequency, composting of spent litter will proceed at a faster rate, thus reaching maturity quicker (74 days). Furthermore, this turning frequency will help eliminate the phytotoxins in the spent litter much faster than turning every 7 days. However, since turning the piles every 2 days is more labour intensive, it is suggested that turning every 4 days be the practical turning frequency for composting of spent litter.