CHANGES IN MICROBIAL-POPULATION NUMBERS DURING THE COMPOSTING OF PINE BARK

Microorganisms associated with the composting of pine bark were enumerated by plating. Microbial numbers increased concurrently with temperature when composting of the bark was initiated by nitrogen addition, and remained high during stabilisation of the compost. The numbers of bacterial colony forming units (CFU) were higher than fungal CFU throughout the composting process, of both mesophilic and thermophilic microorganisms (grown at 30 and 60-degrees-C, respectively). Urea and chicken litter additions to bark resulted in greater bacterial numbers than nitrate addition. Mesophiles and thermophiles were fairly evenly distributed throughout the compost heaps. It is suggested that many of the microorganisms bringing about pine bark composting are thermotolerant. They may not only be able to survive a wide range of temperatures, but also to grow actively at temperatures between 25 and 60-degrees-C.