Co-Inoculation of <i>Trichoderma harzianum</i> and <i>Bradyrhizobium</i> Species Augment the Growth of <i>Schizolobium parahyba</i> var. <i>parahyba</i> (Vell.) Blake Seedlings

The adoption of “consortium” of potential microorganisms can optimize the forest seedling production process. The objective of this study was to evaluate in greenhouse conditions the effect of co-inoculation between <i>Trichoderma harzianum, Bradyrhizobium diazoefficiens</i>, and <i>B. elkanni</i> on the growth of <i>Schizolobium parahyba</i> var. <i>parahyba</i> (Vell.) Blake seedlings. The treatments consisted of fungi strains (<i>T. harzianum</i> ESALQ 1306); bacteria strains (<i>B. elkanni</i> (SEMIA 5080) + <i>B. diazoefficiens</i> (SEMIA 587)); consortium (<i>Trichoderma +Bradyrhizobium</i>), and a control treatment. The seeds were sown, and evaluations were carried out 120 days after sowing. The variables analyzed were shoot height (SH), stem diameter (SD), root length (RL), shoot fresh mass (SFM), root fresh mass (RFM), total fresh biomass (TFM), shoot dry mass (SDM), root dry mass (RFM), total dry biomass (BIO), and Dickson quality index (DQI). The evaluated microorganisms proved to be effective in the production of <i>S. parahyba</i> var. <i>parahyba</i>, with emphasis on co-inoculation for growth parameters, promoting an increase in SH (23%), SD (36%), and RL (84%). For mass, non-inoculated seedlings (control) obtained a decrease of 67% (TFM) and 83% (BIO) compared to co-inoculation. The results indicate a promising method in seedling production; the biostimulators allowed the increase in plant development, which led to success in the morphometric indices. The mechanisms involved in the co-inoculation of microorganisms’ consortium in promoting the growth of native wood species to allow their production on a large scale in the silvicultural sector are still scarce, and new research is needed to elucidate the physiological and biochemical mechanisms involved.