Foliar nutrient concentrations and antioxidant enzyme activities in wheat grown in the cerrado as influenced by nitrogen sources and plant growth-promoting bacteria

Biological nitrogen fixation is a promising strategy to reduce reliance on synthetic nitrogen fertilizers. This study evaluated foliar inoculation with Methylobacterium symbioticum (Blue N™) and Azospirillum brasilense (Masterfix Gramineas™), alone or combined, in wheat (Triticum aestivum L. cv. TBIO Calibre) under Cerrado abiotic stresses and nitrogen (N) volatilization losses. Field trial (2024 season) with five treatments over basal NPK 15.15.15: T1(no urea aplication); T2 (+ 72 kg ha⁻¹ N-urea+NBPT); T3(+ 250 mL ha⁻¹ Masterfix Gramineas™); T4 (+ 333 g ha⁻¹ Blue N™); T5(+ 250 mL ha⁻¹ Masterfix Gramineas™ + 333 g ha⁻¹ Blue N™) at V3 stage. Co-inoculation (T5) increased foliar N (6.6%), phosphorus (P) (7.5%), potassium (K) (12.8%), zinc (Zn) (12.5%), manganese (Mn) (3.1%) and boron (B) (11.1%) versus T1; A. brasilense alone (T3) increased K (10.4%), Zn (5.5%) and B (122.2%), representing the greatest boron accumulation among all treatments; urea+NBPT (T2) only excelled in chlorophyll b (15.9%). Peroxidase activity was reduced Urea+NBPT (T2) (87.7%), A. brasilense alone (T3) (79.7%), M. symbioticum alone (T4) (46.8%) and co-inoculation (T5) (93%) compared to T1. Foliar co-inoculation of A. brasilense + M. symbioticum optimizes nutrient uptake, strengthens antioxidant defenses and enhances the physiological response capacity of wheat under field conditions, offering a sustainable alternative to synthetic nitrogen in wheat grown in the Brazilian Cerrado.