Organic Carbon Sequestration Capacity of Soils of Akwa Ibom State, Nigeria

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International Journal of Research and Scientific Innovation (IJRSI) | Volume VI, Issue VI, June 2019 | ISSN 2321–2705

Organic Carbon Sequestration Capacity of Soils of Akwa Ibom State, Nigeria

Akpan, U. S.*, Nkanga, N.A.

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Department of Soil Science and Land Resources Management, University of Uyo, Akwa Ibom State, Nigeria

*Corresponding author  

Abstract: – Organic carbon sequestration capacity of soils in Akwa Ibom State was assessed. The aim was to identify the organic carbon sequestration capacity of different parent materials and landuse types in the state. Based on the satellite imageries, geological and topographic maps, the study area (Akwa Ibom State) was grouped into four major mapping units to reflect the parent materials, namely: coastal plain sand, sandstone, shale and beach ridge sand. Also, four land use types namely; cultivated farmland, oil palm plantation; homestead and secondary forest of 3 years and above were selected for the study. In each parent material and land use type, three representative locations were selected for sampling. In each sampling location, profile pit was dug and soil samples were collected at a designated depth of 0-20, 20-60, 60-100cm. The core samples were also collected at the same depth for bulk density and hydraulic conductivity-determinations in the laboratory. The study revealed that beach ridge sand soils had the highest organic carbon sequestration capacity, followed by coastal plain sand, followed by sandstone while shale soils had the least in the order: beach ridge sand > coastal plain sand > sandstone > shale. In term of landuse types, homestead or compound farmland had the highest organic carbon sequestration capacity, followed by oil palm plantation and secondary forest of 3-5 years while cultivated farmland had the least in the order: homestead > oil palm plantation > secondary forest > cultivated farmland. Among the organic matter fractions, silt + clay fraction had the highest organic carbon storage capacity, followed by encapsulated POM while free POM had the least storage capacity. In term of soil depth, 60-100 cm soil depth had highest organic carbon storage capacity, followed by 20-60 cm while 0-20 cm had the least. Therefore, in the choice and management of the soil for efficient and sustainable organic carbon source and sink, beach ridge among parent materials and homestead or compound farmlands among landuse types have higher organic carbon sequestration potentials than others.