MOBILIZATION OF P AND CD FROM ROCK PHOSPHATES BY RHIZOSPHERIC MICROORGANISMS (PHOSPHATE-DISSOLVING BACTERIA AND ECTOMYCORRHIZAL FUNGI)

Some rock phosphates used as fertilizers or to produce fertilizers con tain cadmium and have been suspected to increase trace element content in soils. The bioavailability (immobilization, solubilization) of Cd and P from three rock phosphates (from West Africa and East USA) has b een investigated, with phosphate-dissolving microorganisms (two ectomy corrhizal fungi P. tinctorius and S. granulatus and a bacterium Agroba cterium sp.) in pure culture and in pine (Pinus sylvestris L.) rhizosp here. In pure culture the fungi accumulated more Cd than the bacterium . In pine rhizosphere, the uptake of P and Cd by the plant increased w ith bacterial inoculation. The bioavailability of Cd from the differen t rock phosphates was less related to their Cd content than to their c ristallinity and solubility, and was relatively higher than P one.