Effects of phosphorus fertilization and inoculation of Bradyrhizobium and mycorrhizal fungi on growth of Mimosa caesalpiniaefolia in an acid soil

The purpose of this work was to study in an unsterilized acid soil the response of the tropical tree legume Mimosa caesalpiniaefolia to phosphogypsum as a P-fertilizer compared with soluble phosphorus fertilizer and to evaluate the interaction of P fertilization with Bradyrhizobium spp and vesicular arbuscular mycorrhizal fungi (VMF) (Glomus spp and Gigaspora spp) inoculations. A sandy clay red yellow latosol representative acid soil from the forest humid zone of Pernambuco, Brazil was used. P-fertilizer treatments equivalent to 40 kg P ha−1, were applied as triple superphosphate (TSP), phosphogypsum (GP) or a mixture of both. Plants were harvested 80 d after seed germination. P-sources increased mycorrhizal infection only when plants were not inoculated with rhizobia strains, suggesting that native mycorrhizal fungi are not able to develop efficiently in this soil, and the VMF-used groups did not significantly affect any of the factors analysed. In summary, it was concluded that in unsterilized acid soil without P-addition Badyrhizobium strain NFB 577 seemed to be more effective, but when P-fertilizer was used both strains were similarly effective. TSP showed the best results, but PG can be used as a P-fertilizer when combined with a suitable rhizobia strain.