MANAGEMENT of TROPICAL SOILS and ITS EFFECT ON CARBON Sequestration.

To evaluate the agronomic practices that increase the fertility and facilitate carbon sequestration of fragile soils in the tropics, we analyzed six field experiments, which included green residues application established on a sandy soil (ultisol), three tillage systems on a loam silty soil (inceptisol), loam clay soil (vertisols) and clay soil (vertisols), manure and fertilizer application on a loam soil (mollisol), and silvopastoral system on loam clayed soil (alfisol). In general, no tillage increased the mineralizable C; it represented approximately 3% of the organic C total. Soil fertility differed between management of cultivation and silvopastoral system with favorable soil reaction, improved nutrient reserves and availability in the later system. The soil physical structure was significantly affected by tillage and residues applications, with greater proportion of large macroaggregates in no tillage than tillage system. Furthermore, treatments of no tillage (NT) provided higher proportion (?30%) of C sequestrated compared to conventional tillage after several years of no tillage. The carbon sequestration rate ranged from 1.2 to -0.2 Mg C ha-1 y-1. The higher rate of carbon sequestration was correlated (P < 0.05) to management practices (NT, manure), but not to soil order.