Co-composting of pig manure with leaves

The increase in the market price of sawdust makes it a less attractive bulk ing agent for pig manure composting. Hence, it was the aim of this project to evaluate the feasibility of co-composting pig manure with leaves with sp ecial emphasis on its effects on compost maturity and quality. Two piles we re prepared with one pile (Pile A) just constituted of pig manure and sawdu st at a mixing ratio of 3:2 (w/w, fresh weight), while the other one (Pile B) with pig manure, sawdust and leaves at 3:1:1 ratio (w/w, fresh weight) t o achieve a C/N ratio of 30. Each 8 m(3) heap was turned and mixed every 3 days to provide sufficient aeration and the moisture content was kept at 60 -70% (w/w) throughout the composting period. After 49 days of composting, d issolved organic carbon (DOC), soluble NH4-N, C/N-solid and C/N-aqueous, of pile A decreased to <5%, 400 mg kg(-1), 20 and 6, respectively, indicating a high degree of maturity, while pile B with leaves required only 35 days. Seed germination index (Gl) of pile A increased to 66.5% at day 49, while pile B to 52.4% at day 35, which was higher than the phytotoxin-free level of 50% recommended for agricultural use. This demonstrated that the additio n of leaves enhanced the humification process and shortened the time requir ed for maturation and stabilization of pig manure composting. Therefore, it is recommended to co-compost pig manure with leaves to provide a means to reutilize this waste and in the same time to reduce the dependence on sawdu st as a bulking agent.