Composting of pine and eucalyptus barks

Abstract

Abstract Pine ( Pinus sylvestris L.), eucalyptus ( Eucalyptus globulus L.) and mixed bark heaps with several shapes and sizes were built in the open air and their composting processes were followed. During heap construction, urea was added so that C/N ratios were, approximately, 30 or 15. Temperature, moisture and pH records were made through at least twelve months. Reading and sampling were carried out at various points in the heaps. Compressed air was injected for twelve months, through a performed metallic tubing, lying near the bottom of the heap. Once a month, the heaps were mechanically mixed. Identification of some of the microorganisms present during composting was done, and the cellulolytic organisms were counted in the mesophile, thermophile and decreasing temperature stages. A study of the evolution of certain bark characteristics, either physical (water-holding capacity and pore volume), physico-chemical (ion retention capacity of ammonium, nitrate, phosphate and potassium) or chemical (cellulose, ash, humic and fulvic acids content) was performed. Greenhouse experiments dealing with the use of composted bark as a substrate and the American oak, Quercus rubra L., as a specimen of forest species were carried out.The composted barks proved to be quite good substrates.