GONCALVES, Paula    CASTRO, Isabel Videira e. Effects of Sewage Sludge Application in the Diversity of Rhizobial Population. []. , 12, 1, pp.95-104. ISSN 0870-6352.

The use of sewage sludge in agriculture is being practised throughout the world with beneficial effects on the productivity of cultures, on the organic content of soils, and on their capacity of cation exchange and water retention. However, sewage sludge can contain high concentrations of heavy metals and other contaminants that may cause serious environmental problems, affecting both plants and soil microorganisms, especially Rhizobium bacteria (nitrogen fixers). To evaluate the potentialities of an urban sewage sludge from Lisbon as a fertiliser for underground clover and grass pastures, a field experiment was carried out in the grounds of Quinta do Marquês (Oeiras). The aim of this work was to monitor changes in the genetic diversity of Rhizobium leguminosarum biovar trifolii population in soils amended with different quantities of sewage sludge (5, 10, 20 and 50 t ha^-1). The results of this study permitted us to verify that changes took place at the plasmid-DNA level in the genetic composition of the Rhizobium isolates tested, primarily where treatments had been amended with high quantities of sewage sludge (20 and 50 t ha^-1).

: sewage sludge; Rhizobium; genetic diversity; plasmid profile.

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