COMPARING ORGANIC FRACTION CHANGES OF ONE COMPOSTING AND TWO VERMICOMPOSTING PROCESSES AIMED TO PRODUCE QUALITY COMPOST AND VERMICOMPOSTS FOR SOILLESS CULTIVATION OR AS SOIL CONDITIONER

One composting and two vermicomposting processes applied to a vegetable waste mixture were compared at selected stages for their chemical characteristics. The starting material consisted of a mixture of milled residual tomato crop biomass and ground almond shells (75:25, v:v). The compost was produced by a combined system (Rutgers + pile turning) (COM process). For one of the vermicomposts the fresh waste mixture was first composted (only active phase) and then vermicomposted with Eisenia Andrei and E. fetida earthworms (C+V process). Finally, for the second vermicompost, the fresh waste mix was directly vermicomposted with E. Andrei and E. fetida earthworms (VER process). The three materials were analysed at five stages of each process for a selection of parameters with organic character (total organic matter, total organic carbon, total nitrogen, water-soluble carbon, alkali-extractable carbon, humic and fulvic acid carbon, lignin, hemicellulose and cellulose). COM, C+V and VER showed significant differences in organic matter, extractable carbon, humic and fulvic carbon, water-soluble carbon, lignin and cellulose contents both within process among stages and among the processes themselves. The study of the changes of the organic fraction throughout the three processes was used to determine the maturity and stability parameters of the materials particularly at the latter stages, and helped to understand the final organic characteristics of the compost and vermicomposts. However, the indices proved useful to assess maturity and stability of the organic materials at the latter stages of COM, C+V and VER. Other indices than the ones selected for this study should be tried for the initial stages of COM, C+V and VER.