INFLUENCE OF PARENT MATERIALS AND LAND USE ON SOIL CARBON SEQUESTRATION IN SOUTHERN NIGERIA

A study was conducted to determine the effect of parent materials and land use on C sequestration in southern Nigeria. The experimental design used for the study was a 2 x 5 x 3 factorial in RCBD. The factors were land use (managed tree croplands (MTC) and continuously cultivated croplands (CCC), parent material (coastal plain sands at the Forestry Research Institute of Nigeria (FRIN), Isieke; Shale at the National Horticultural Research Institute (NIHORT), Okigwe, Imo Clay Shale at the Anambra-Imo River Basin Development Authority (AIRBDA), Agbala; Coastal Plain sands at the Niger Delta Basin Development Authority (NDBDA), Kpong and Alluvium at the Niger Delta Basin Development Authority (NDBDA), Isiokolo and soil horizon depths (0-19, 20-39 and 40-100 cm). Physical properties ranged from 49-85 %, 9-40 %, 4-22 % and 1.35-2.15 gcm-3 for sand, clay, silt and bulk density in MTC and 60-81 %, 9-30 %, 5-13 % and 1.38-2.15 gcm-3 for sand, clay, silt and bulk density in CCC. The textural class ranged from loamy sand to sandy loam at the surface and sandy clay loam to sandy clay at the subsurface. Soil reaction were extremely acid to strongly acid (pH 4.4-5.5) for MTC and very strongly acid to moderately acid (pH 4.5-5.6) for CCC. Soils under MTC sequestered higher (p<0.05) amount of C across the soil depths relative to arable croplands. SOC pool in MTC soil was within the ideal range for mitigating climate change and environmental quality control, whereas CCC land utilization type was below the threshold level. Coastal plain sands of FRIN- Isieke had highest (p<0.05) amount of SOC pool (575.80 MgCha-¹), while the alluvial soils of NDBDA- Isiokolo gave the lowest (409. 50 MgCha-¹). The study revealed that SOC sequestration is a function of land use, parent material and depth. Therefore, the soil conservation practices associated with CCC under the different parent materials in the studied area should be re-evaluated, this is because reduction of SOC in CCC increased oxidation of SOM, thereby leading to SOC losses to the atmosphere and this may also accelerate global warming.