AVALIAÇÃO DE PARÂMETROS RELACIONADOS A FIXAÇÃO BIOLÓGICA DE NITROGÊNIO EM SOJA cv. TMG 2165 IPRO PRÉ-COINOCULADA EM DIFERENTES MOMENTOS ANTES DA SEMEADURA

The objective was to evaluate parameters of biological nitrogen fixation in soybean subjected to different treatments: T1 - control without the use of commercial inoculant; T2 - chemical nitrogen fertilization; T3 - commercial inoculant based Bradyrhizobium applied to the seeds on the sowing day; use of commercial inoculant containing Bradyrhizobium and Azospirillum bacteria applied at 0, 7 and 15 days before sowing (DBS), treatments T4, T5 e T6, respectively. In R2, the following parameters were evaluated: number of nodules and dry mass in the main root, secondary roots and total; shoot and total dry mass and nitrogen content in the soot (NCS). In R8, the accumulated nitrogen content in the grains (NCG) was measured. From the results obtained, it can be noted that for the nodulation parameters (nodular number and dry mass) the treatments that stood out were related to co-inoculation (T4, T5 e T6) without statistical difference regarding the period of application of the inoculant. With regard to NCS, there was a greater increase in treatments T4 and T2, which did not differ from each other and presented mean values of 33.84 and 33.23 kg ha-1, respectively. For NCG, T4 stood out with 58.43 kg ha-1, despite having statistical similarity to treatments that used the same inoculant applied to 7 (T5) and (T6) DBS, as well as T2 and T3. It can be concluded that the parameters to biological nitrogen fixation did not suffer a negative influence due to the application of early co-inoculation up to 15 days before soybean sowing.