The effects of rhizobial and mycorrhizal inoculation, nitrogen and phosphorus fertilization on nodulation, mycorrhizal colonization and initial growth were examined in Brazilian native plants, Enterolobium contortisiliquum (Vell. Conc.) Morong, Inga laurina (Sw.) Willd., Lonchocarpus muehlbergianus Hassl and Platypodium elegans Vogel. The experiment was carried out in a glasshouse using plastic bags filled with a mixture of sandy soil from riparian forest and vermiculite (2:1) amended with basal nutrients including NP, P and N and infected with rhizobia (r), mycorrhiza (m) or both (rm), amounting seven treatments: NP, P, P+r, P+rm, N, N+m and N+rm, with ten replications each. The plants were analyzed at 120 and 255 days after sowing. P deficiency negatively affected growth and nodulation of all species. Autochton arbuscular mycorrhizal fungi (AMF) colonized host roots and fungal inoculations did not enhance mycorrhizal colonization, which was also favored by added P. Nodulation was relatively higher in E. contortisiliquum and L. muehlbergianus, mainly in treatments containing P, and with rhizobial inoculation (P+r). Plants from these treatments developed better than others and, despite the rhizobia inoculated had no synergistic relationship with inoculated AMF, they also showed the best percentages of mycorrhizal colonization. Moreover, these two species showed highest rates of acetylene reduction and highest leghemoglobin content. These results suggest that E. contortisiliquum and L. muehlbergianus can have advantages for establishment in soils with low nitrogen levels.
rhizobia; dual inoculation; Enterolobium contortisiliquum; Inga laurina; Lonchocarpus muehlbergianus; Platypodium elegans
