CARBON SEQUESTRATION AND ORGANIC FRACTIONS IN A MAIZE SILAGE AND BRACHIARIA INTERCROPPING SYSTEM IN TROPICAL SOIL

In the face of the global challenge of mitigating climate change, soil carbon sequestration emerges as an important strategy, especially in tropical soils, where the rapid decomposition of organic matter requires management practices that promote its accumulation. The integration of intercropped crops, notably maize silage production combined with Brachiaria (Urochloa spp.), represents a sustainable alternative to increase carbon stocks and improve soil quality in the Brazilian Cerrado. This study evaluated the impact of the maize silage and ruzigrass (Urochloa ruziziensis) intercropping system, combined with different nitrogen sources, on carbon sequestration in a Red-Yellow Latosol. A randomized block design with split plots was used, with the experiment conducted in Nazareno municipality, state of Minas Gerais, Brazil (21°15'40.3"S, 44°31'02.1"W). To determine carbon content, light organic matter (LOM) and total organic carbon (TOC) were analyzed using the dry combustion method (Nelson & Sommers, 1996) with a carbon elemental analyzer. The comparison included maize monocropping and intercropping, with treatments involving calcium ammonium nitrate (CAN), urease-inhibitor-treated urea (NBPT), conventional urea, and a control without nitrogen application. Soil samples were collected at different depths to quantify TOC and the LOM, as well as to assess microbial activity and soil physical structure indicators. The data were tested for normality (Shapiro-Wilk) and homogeneity (Bartlett), and transformed if p < 0.05. The results showed that in the 0–5 cm layer, the intercropping system reached 28 g/kg of TOC with the CAN treatment, compared to 23 g/kg in monocropping. LOM was significantly higher in the intercropping system, reaching 5.2 g/kg, a 22% increase over monocropping. Additionally, there was a 25% increase in soil basal respiration and an elevation in the metabolic quotient (qCO₂) in the intercropping system, indicating more intense microbial activity, in the 0–5 cm layer. These findings suggest that intercropping not only reduces organic matter losses compared with maize silage but also enhances the resilience of tropical soils, promoting structural improvements. Furthermore, this integrative strategy aligns with the SDGs 2, 13 and 15, contributing to greenhouse gas emissions mitigation and strengthening agricultural sustainability. Although the two-year experimental period-imposed limitations, the data reinforce the potential of intercropping as a viable model for sustainable agricultural practices, highlighting the need for future research to extend the study period and deepen the understanding of carbon stabilization mechanisms in tropical soils.