Abstract
Bark compost is a useful medium for potted plants. As immature compost, however, it can damage plants by generating ammonia and causing nitrogen starvation, so evaluation of maturity is indispensable when using it as compost. In the primary process of compost fermentation, microorganisms generate ammonia by resolving easily biodegradable organic nitrogen compounds, and other microorganisms immobilize this ammonia. As the amount of easily biodegradable organic nitrogen compounds decreases, the activity of these microorganisms declines. We investigated the decrease in the ammonia content as an index of microorganism activity, and discussed the relationship between the ammonia content and the number of days of composting. As much ammonia was detected from the compost in the early days of fermentation, we decided that compost in the primary fermentation process could be evaluated by the detection of much ammonia. Ammonium sulfate was added to compost that was estimated to be in the process of secondary fermentation, and the ammonia content was measured during 72 hours. The compost fermented longer had less decrease than that composted for fewer days. We could, therefore, suggest that the compost in the secondary fermentation process could be subdivided according to an index of maturity by the ammonia decrease during the 72 hours after the addition of ammonium sulfate.
