Dual inoculation of a woody legume (Centrolobium tomentosum) with rhizobiaand mycorrhizal fungi in south-eastern Brazil

The integration of N-2 fixing trees into stable agroforestry systems in the tropics is being tested due to their ability to produce high biomass N and P yields, when symbiotically associated with rhizobia and mycorrhizal fung i. The growth of Centrolobium tomentosum Guill. ex Benth, a native legumino us tree from the Brazilian Atlantic Forest, was assessed with dual inoculat ion of Rhizobium spp and mycorrhizal fungi under field conditions. Complete fertilization was compared to treatments of inoculation with selected rhiz obia strains BHICB-Ab1 or BHICB-Ab3, associated or not to arbuscular mycorr hizal (AM) fungi. The dual inoculation increased the height and growth in r elation to the plants treated with rhizobia alone. Plants inoculated with s train BHICB-Ab1 and arbuscular mycorrhizal fungi (AMF) exhibited an increas e of 56% dry matter over uninoculated control and nitrogen accumulation was greater than with BHICB-Ab3 inoculated plants. Strain BHICB-Ab1 presented a synergetic relationship with mycorrhizal fungi since the combined inocula tion with BHICB-Ab1 enhanced plant height and dry weight more than single i noculation while the growth of BHICB-Ab3 plants was not modified by AMF ino culation. Arbuscular mycorrhizal fungi enhanced plants survival and seemed to favour the nodule occupation by rhizobia strains as compared to the non- mycorrhizal plants. Inoculation with selected rhizobia and AMF improved the growth of C. tomentosum under field conditions.