INFLUÊNCIA DA COINOCULAÇÃO DE SOJA COM Bradyrhizobium E DIFERENTES CEPAS DE Azospirillum EM PARÂMETROS DE FIXAÇÃO BIOLÓGICA DE NITROGÊNIO

The objective was to evaluate the efficiency in parameters of biological nitrogen fixation (BNF) of new strains of Azospirillum for coinoculation with Bradyrhizobium in soybean. For this, a fiel experimentw was set up with the following treatments: 1 - negative control without inoculant; 2 - positive control com 200 kg ha-1 of chemical nitrogen fertilizer; 3- inoculation with Bradyrhizobium (B); 4 -coinoculation of B with Azospirillum brasilense; 5 - coinoculation B + strain 1; 6 - coinoculation B + strain 2; T7 - coinoculation B + strain 3 and 8 - coinoculation B + strains 1, 2 and 3. At flowering, 5 plants were collected per experimental plot. The evaluated parameters were: number and dry mass of nodules on the main root (NMR, DMMR), on the secondary roots (NSR, DMSR) and total (NTR, DMTR); dry mass of aerial part (DMAP) and of the root (DMR). In relation to NSR and NTR, treatment 4 provided a greater increment of nodules in the secondary roots and a total of respectively 25 and 31,87 nodules plant-1 in relation to the others tested. For NMR treatments 3 and 4 were similar with means of 6,7 and 6,87 nodules plant-1, not statistically diferente from treatments with others Azospirillum strains (5, 6 and 7). As for DMMR, DMSR and DMTR, 4 and 3 stood out in relation to these parameters and were superior to treatments (5, 6, 7 and 8). Only for DMR and DMAP chemical nitrogen fertilization (2) stood out statistically, with the first parameter statistically similar to treatment 4 and second to treatment 8. It can be concluded that the new strains did not stand out in the parameters of BNF, with coinoculation with Azospirillum brasilense more efficient. Keywords: Lineage selection, Mixed inoculation, Glycine max.