| An experimental laboratory study was undertaken to investigate the convective airflow which develops in compost masses and the effect of passive and active aeration on nitrogen (N) and carbon (C) losses of compost at three different levels of dry matter (d.m) with four different C sources (pine shavings, grass hay, oat straw and wheat straw). Each bulking agent was individually mixed with swine slurry and composted at 40, 32 and 28% d.m. Duplicate mixtures were aerated for 21 days (14 days for one of the pine shavings trials) both in active and passive conditions in 100L composters and their temperature was monitored every 3 hours. The passively aerated compost demonstrated temperature regimes similar to that of the actively aerated compost reaching and exceeding 55°C for 3 days. The initial airflow resistance of the composts was found to be lower than the final. The convective airflow of the compost was correlated with time and to the difference in ambient and compost temperature. The 32% d.m. content and the wood shavings compost produced higher convective airflows. The statistical significance of the effects of aeration method, d.m. level, and C source on N conservation was tested. Only the C source had a significant effect (P ≤ 0.05). The hay amended with urea had the lowest N losses (22.4%), followed by oat straw, hay, wood shavings amended with soybeans, wheat straw and wood shavings with losses of 41.4, 53.4, 53.6, 55.2% and 68.5% respectively. The C losses were strongly related to the N losses, except for the hay amended with urea compost. The oat straw loss the most C (51.4%), followed by hay, wheat straw, wood shavings amended with and without soybeans, and hay amended with urea with losses of 37.4, 35.8, 25.4%, 13.5% and 12.19% respectively. (Abstract shortened by UMI.)... |
