ESTOQUE DE CARBONO NO SOLO EM SISTEMA DE CONSÓRCIO DE MILHO EM SUCESSÃO A CANA-DE-AÇÚCAR SUBMETIDOS A DISTINTAS DOSES DE AZOSPIRILLUM BRASILENSE E FONTES DE NITROGENIO

Abstract

Assessing carbon stocks at different depths is particularly important, since deeper layers tend to store more stable and persistent forms of carbon. Despite these advances, research analyzing the interaction between nitrogen sources and doses of microbial inoculant on carbon stocks in different soil layers is still scarce, especially in integrated systems such as corn and sugarcane. Thus, this study aimed to evaluate the effect of applying doses of Azospirillum brasilense associated with nitrogen sources (nitrate and urea) on organic carbon stocks at three depths in soil cultivated with corn intercropped with sugarcane. The experiment was conducted in Chapadão do Céu – GO. The experimental design was a randomized complete block design in a factorial scheme, with four replications. The treatments consisted of doses of Azospirillum brasilense (A1 = 0, A2 = 100, A3 = 200, A4 = 300 mL ha⁻¹; strains AbV5 and AbV6; 2 × 10⁸ CFU mL⁻¹) applied during seed inoculation, and two N sources (ammonium nitrate and urea). The plots were composed of nine rows of corn (10 m long), with the three central rows considered the useful area. sixty days after germination, soil samples were collected at three depths: 0–10 cm (C1), 10–20 cm (C2), and 20–40 cm (C3). The results indicate that the use of nitrate as a nitrogen source associated with higher doses of inoculant favors the accumulation of carbon in the soil, especially in subsurface layers. urea, on the other hand, showed the opposite behavior, with a reduction in stocks as inoculant doses increased, possibly due to losses from volatilization and lower efficiency in utilization. These findings reinforce the importance of choosing the appropriate nitrogen source and inoculant dose to maximize biological fixation, root growth, and consequently, carbon input to the soil.