Organic amendments, green manure and plant residues incorporated into the soil are the main source of organic carbon and nutrients in organic farming. Their decomposition rate is crucial for accumulation and long-term storage of organic matter in soils. The decomposition rate is strongly regulated by the chemical composition of the organic materials and the pedoclimatic conditions. In this study, the decomposition of compost from olive mill waste, goat manure and Medicago sativa (Alfalfa) was followed in Lebanese soils using the litterbag technique. Mass losses, carbon turnover and nutrients release were evaluated through winter and springtime in three Lebanese soil types on the basis of the decomposition rates. A rapid mass loss was found in Alfalfa shoots and roots 30 days after incorporation. Manure and compost were more persistent.
[...]
Labile forms of carbon and nitrogen were released during the first few weeks after incorporation. Moreover, C/N ratio cannot be used as unique parameter to predict the decomposition rate. Other parameters should be determined such as the humification rate. Pedoclimatic conditions played an important role in the organic matter decomposition, with a greater release in well-drained soils.
