Soil Organic Carbon Stocks and Aggregate Stability of Different Land Use Types in Southeastern Nigeria

Land use types influence soil organic carbon (SOC) storage and soil structure, with implications for ecosystem functioning and sustainable C management. Triplicate samples of topsoil (0-30 cm) and subsoil (30-60 cm) collected from fallow, forest, and oil palm plantation (OPP) land use types in Iheaka, south eastern Nigeria were set up as a 3 x 2 factorial experiment in a completely randomized design. The physi & scy;ochemical properties of the soils, including SOC stocks, were examined. The fallow soil was sandy clay loam while the forest and OPP soils were sandy loams (Ultisols). Saturated hydraulic conductivity was highest in the soil for OPP > forest > fallow land uses. In contrast to the fallow land, the OPP had the highest percentage aggregate stability and mean weight diameter, including a higher percentage of >1.00 mm macroaggregates than <0.50 mm microaggregates. The proportion of >1.00 mm macroaggregates was highest in the topsoil, while <0.25 mm microaggregates dominated the subsoil. Land use significantly affected SOC, total N, available P, K+ and Na+ concentrations, including CEC, which were the highest in the fallow land. Soil C stocks (Mg C ha(-1)) were higher in the fallow (31.75) = forest (24.24) > OPP (14.57) land use types. Carbon stocks were mainly concentrated in the topsoil and were more pronounced in the forest land where SOC losses through water erosion and runoff predominate. The ability of fallows to store large C stocks is essential for sustainable land use management and reduction of CO2 emissions in the context of global protection against climate change.