ABSTRACT This study aimed to evaluate the impact of the combination of olivine melilitite powder with bacterial inoculation on soil microbiological attributes. The experiment was conducted in a randomized block design (n = 4), with the following treatments: chemical fertilizer (CF), fertilizer reduction + remineralizer (FRR), fertilizer reduction + remineralizer + Azospirillum (FRA), fertilizer reduction + remineralizer + Bacillus (FRB), and fertilizer reduction + remineralizer + co-inoculation of Azospirillum and Bacillus (FRC). A 25 % reduction of chemical fertilizer was tested in FRR, FRA, FRB, and FRC for two years. The microbial biomass carbon (MBC), soil basal respiration (SBR), microbial quotient (qMIC), metabolic quotient (qCO 2 ), and grain yield (GY) of maize were evaluated. The results indicated that the soil from treatments FRA (515.72 mg microbial C (carbon) and 2.28 %), FRB (547.43 mg microbial C and 2.65 %), and FRC (529.64 mg microbial C and 2.38 %) exhibited the greater values of MBC and qMIC. The highest qCO 2 values were found in the soil of FRR (5.55 µg C-CO 2 µg MBC) and CF (5.84 µg C-CO 2 µg MBC), indicating stress effects on the microbial community. However, following the first cultivation, this effect was reduced in FRR due to the application of olivine melilitite. Moreover, MBC (R 2 = 0.46), qMIC (R 2 = 0.35), and SBR (R 2 = 0.79) exhibited a positive correlation with maize GY, while qCO 2 (R 2 = –0.33) presented a negative correlation with GY. This suggests that bacterial inoculation associated with olivine melilitite may have influenced the results. In conclusion, the application of olivine melilitite and inoculation with beneficial bacteria has been demonstrated to enhance soil microbiological attributes and maize yield. n 4, 4 , 4) CF, (CF) (FRR) (FRA) (FRB) coinoculation co FRC. . (FRC) years MBC, (MBC) SBR, (SBR) qMIC, (qMIC) ) GY (GY evaluated 515.72 51572 515 72 (515.7 (carbon 228 28 2.2 %, 547.43 54743 547 43 (547.4 265 65 2.6 529.64 52964 529 64 (529.6 238 38 2.3 5.55 555 5 55 (5.5 CCO CO 5.84 584 84 (5.8 community However cultivation Moreover R 0.46, 046 0.46 0 46 0.46) 0.35, 035 0.35 35 0.35) 0.79 079 79 –0.33 033 33 conclusion (CF (FRR (FRA (FRB (FRC (MBC (SBR (qMIC 515.7 5157 51 7 (515. 22 2. 547.4 5474 54 (547. 26 6 529.6 5296 52 (529. 23 3 5.5 (5. 5.8 58 8 04 0.4 03 0.3 0.7 07 –0.3 515. (515 547. (547 529. (529 5. (5 0. –0. (51 (54 (52 ( –0 –