NITROGEN MINERALIZATION OF IMMATURE MUNICIPAL SOLID WASTE COMPOST

Nitrogen (N) mineralization of a municipal solid waste compost (MSWC) blended with two soils of different textures (clay and sandy) and the emergence of ryegrass plants treated with different N fertilizers were studied. Compost-soil samples showed initially a strong immobilization of the mineral N present in the blends. Only after 12 weeks of incubation, positive mineralization was observed in both soils, although it was more intense in the case of the sandy soil. Mineralization process was modeled with a one pool equation, but only in the case of the sandy soil, the model fitted experimental data significantly. Plants showed at the initial emergence stages, differences in biomass and N-content related to the N immobilization observed in the soils treated with MSWC. It may be concluded that these composts must be applied to soils three months before sowing or before the time that a crop needs a continuous supply of N.