SOIL CARBON STOCKS UNDER OFF-SEASON DIVERSIFICATION SYSTEMS IN THE CERRADO

Carbon (C) is a central component of soil organic matter (SOM), essential for the functioning and sustainability of tropical agricultural systems. Crop diversification, including grasses and legumes during the off-season, has been recommended as a promising practice to increase soil C inputs. However, due to the dynamics of C in the soil, the response to these practices can be slow, particularly in weathered environments. This study aimed to evaluate the effect of off-season diversification on Soil Carbon Stocks (SCS) in a soybean-maize system in the Cerrado biome. The experiment was conducted over four years in Sorriso-MT, Brazil, on a clayey Oxisol, using a randomized complete block design with four replications. Three treatments were evaluated: 1)maize; 2)maize+brachiaria; and 3)maize+brachiaria+crotalaria. Soil samples were collected at the 0–10, 10–20, and 20–30 cm depths to determine bulk density and C content, analyzed by dry combustion. SCS were corrected to an equivalent soil mass and subjected to ANOVA at a 5% significance level. The results indicated no significant differences among the systems, regardless of soil depth. A vertical C gradient was maintained, with higher values in surface layers and a tendency toward greater stocks in the more diversified systems (26.67<27.18<30.12 Mg C ha-1). The absence of a significant response reflects the cumulative nature of C in soils tropical systems, indicating that longer time periods are required to detect changes. Crop diversification shows potential as a management strategy, but its effects depend on the long-term persistence of the system.