SOIL ORGANIC CARBON LEVELS IN SOILS OF CONTRASTING LAND USES IN SOUTHEASTERN NIGERIA

Land use change affects soil organic carbon (SOC) storage in tropical soils, but information on the influence of land use change on segmental topsoil organic carbon stock is lacking. The study investigated SOC levels in Awgu (L), Okigwe (CL), Nsukka I (SL), and Nsukka II (SCL) locations in southeastern Nigeria. Land uses considered in each location were the cultivated (manually-tilled) and the adjacent uncultivated (4-5 year bush-fallow) soils from which samples at 0-10, 10-20, and 20-30 cm topsoil depth were assessed. The SOC level decreased with topsoil depth in both land uses. Overall, the SOC level at 0-30 cm was between 285.44 and 805.05 Mg ha-1 amongst the soils. The uncultivated sites stored more SOC than its adjacent cultivated counterpart at 0-10 and 10-20 cm depth, except in Nsukka II soils, which had significantly higher SOC levels in the cultivated than the uncultivated site. Nonetheless, at 20-30 cm depth, the SOC pool across the fallowed soils was statistically similar when parts of the same soil utilization type were tilled and cultivated. Therefore, while 4 to 5 years fallow may be a useful strategy for SOC stabilization within 20-30 cm topsoil depth in the geographical domain, segmental computation of topsoil organic carbon pool is critical