Soil Management and Topsoil Quality as Determinants of Residue Decomposition and Nutrient Release in Agroecosystems of the Brazilian Cerrado

Nutrients and carbon cycling processes in integrated production systems are essential for agroecological sustainability in the Cerrado of Northeast Brazil. However, quantitative and process-level understanding remains limited. This study aimed to characterize off-season plant residue decomposition under different production arrangements through the assessment of dry biomass, bromatological composition, and litter decomposition kinetics. The experiment was conducted in the off-season of the 2022/2023 agricultural year at Barbosa farm (Brejo, Maranhão, Brazil), in a Yellow Argisol (Ultisol), with Aw prevailing climate. We evaluated residues of soybean, Urochloa brizantha cv. Marandu, maize, maize + Marandu, Megathyrsus maximus cv. BRS Tamani, Eucalyptus, Eucalyptus + Tamani, and native forest, representing crop–livestock integration (CLI), livestock–forestry integration (LFI), no-tillage soybean (Soybean-NT), and native forest (control). For each treatment, 0.20 × 0.20 m, 2 mm mesh nylon litterbags (nº = 4 replicates) were filled with 20 g of oven-dried plant residues cut into ~10 cm pieces. Litterbags were placed on the soil surface and sampled at 0, 30, 60, and 118 days to estimate the decomposition rate (k), C and N mineralization, and macronutrient dynamics. Residues differed in initial composition, with Eucalyptus and Eucalyptus + Tamani showing higher C contents (41–43%), while Marandu and Soybean-NT had greater concentrations of N (37.8–39.2 g kg−1), P (2.37–2.42 g kg−1), and Mg (2.38–2.83 g kg−1). The Eucalyptus + Tamani mixture exhibited the highest decomposition rate (k = 0.0041), which was about 40% greater than Soybean-NT (k = 0.0026), and faster C release, whereas N in maize residues remained immobilized for up to 118 days. CLI and Soybean-NT enhanced nutrient cycling efficiency, with K+ increasing 17.3-fold (1.1 to 18.9 g kg−1) and N 1.2-fold (1.8 to 2.3%) compared to native forest. Overall, residue quality, especially C/N ratio and lignin, regulated decomposition and integrated systems, particularly LFI, which conferred greater resilience and nutrient cycling efficiency in the Cerrado.