ABSTRACT
Tropical ecosystems play a major role in global biogeochemical cycles. Predominant soils of the humid tropics are Oxisols, Ultisols, Inceptisols, Entisols, Alfisols, Histosols, and Spodosols. The chapter aims to summarize data from several long-term deforestation and soil management experiments conducted at the International Institute of Tropical Agriculture. It presents results of soil analyses for soil organic carbon (SOC) content as affected by deforestation, tillage, cropping systems, mulching, and agroforestry. Soil disturbance and residue management systems influence carbon sequestration through their effects on biomass returned to the soil, rate of oxidation and mineralization of SOC, and losses due to erosion and leaching. Plow-based tillage systems involving soil turnover usually decrease SOC content. The data from a 17-year study under no-till vs. conventional till of an Alfisol in Western Nigeria showed that soil under no-till contained more SOC in the top 0 to 10 cm layer than that under conventional till based on discing the soil to 20-cm depth.
