BIODEGRADABILITY AND MICROBIAL ACTIVITIES DURING COMPOSTING OF POULTRY LITTER

Poultry litter is composted to reduce odor and pathogens and to improv e its quality as a soil amendment. Organic material, e.g., sawdust, is added to increase the C:N ratio to achieve optimum degradation of org anic C and retention of N through microbial biomass formation. However , the relative biodegradabilities of the organic material in poultry l itter and the amendment are usually not known. Furthermore, it is assu med that as microorganisms metabolize organic compounds and produce CO 2, they increase in biomass and, therefore, retain N. In this study, b ench-scale compost reactors were used to determine the relative contri butions of poultry litter and of the amendment (sawdust) to the biodeg radability of a compost mix. Approximately 29% of the volatiles lost f rom the poultry litter mix came from the sawdust. Fiber analyses revea led that only a small portion of cellulose was degraded. Although micr obial subpopulations able to degrade selected macromolecules were pres ent at varying levels, the overall level of microorganisms did not cha nge markedly. Populations capable of degrading bacterial cell walls we re present throughout the composting period, and microbiological assay s indicated that inorganic nutrients were available to support limited microbial growth. These results suggest that N compounds and inorgani c nutrients are recycled, rather than fixed during composting.