Depth Distribution of Organic Carbon Stocks in Tropical Soils with Contrasting Land Uses

Abstract

This study evaluated soil organic carbon stocks under different agricultural land uses (cacao, oil palm, fallow, and secondary forest) with a view to understanding the impact of land use management practices and soil depth on soil organic carbon stocks. The research focused on Ultisols (USDA Soil Taxonomy), a highly weathered soil type classified as Ferric Acrisol (WRB) from Ile-Ife, Nigeria in the year 2022. Soil samples were collected to analyze particle size distribution, bulk density, pH, and organic carbon content, while soil organic carbon stocks were calculated using a standard equation. The results showed that land use had a more pronounced effect on the upper soil horizon compared to deeper layers, with oil palm plantations exhibiting the highest soil organic matter content and soil organic carbon stock concentration in surface soils. These findings suggest that cultivating tree crops and implementing afforestation contribute to carbon storage and protection within the soil. Additionally, the study identified the potential of subsoil horizons to account for more than half of the total soil organic carbon stocks, underscoring the importance of further investigations into deeper tropical soil layers.