Multifunctional roles of Bacillus spp. and Paecilomyces lilacinum: Mechanisms of direct and indirect action in soybean and maize under tropical conditions

ABSTRACT Plant-parasitic nematodes and low soil phosphorus availability constrain crop productivity, highlighting the need for integrated management strategies. This study evaluated the effects of Bacillus spp. and Paecilomyces lilacinum on nematode suppression, phosphorus availability, plant nutritional status, carbon metabolism, and grain yield in soybean and maize. Four greenhouse and field experiments were conducted in São Paulo, Brazil, between October 2022 and March 2023, with bio-inputs applied through seed treatment or in-furrow application. Assessments included root development, nematode populations, soil phosphorus fractions, leaf nutrient concentrations, photosynthetic traits, enzyme activities, and grain yield. Compared with the respective controls, in-furrow P. lilacinum reduced nematode populations at 60 days after emergence by 40.2% in soybean and 26.3% in maize. Soil labile phosphorus increased by 19.7% with seed-applied Bacillus spp. in soybean and by 36.0% with in-furrow P. lilacinum in maize. Seed-applied P. lilacinum also increased net photosynthetic rates by 22.4% in soybean and 14.0% in maize. In-furrow Bacillus spp. and P. lilacinum increased soybean grain yield by 15.6% and 15.0%, respectively. All microbial treatments increased maize grain yield, averaging 6.80%, with no significant differences among treatments. These findings demonstrate improvements in nematode suppression, phosphorus availability, selected physiological traits, and grain yield, with responses depending on crop and application method. Both microorganisms therefore represent promising tools for integrated nematode and nutrient management in tropical cropping systems.