Comparative Assessment of Soil Carbon Sequestration and Carbon Dioxide Emissions from Agroforestry Systems in Kogi East Nigeria

Abstract

This study was conducted to assess the below ground carbon sequestration (soil carbon stock per unit land area) and carbon dioxide (CO2) emissions from agroforestry systems (AFSs) in Kogi East (Ankpa, Dekina, Ofu, Olamaboro, and Omala local government areas) Nigeria. Stratified random sampling was used to select study locations of the agroforestry systems in Kogi East, Nigeria. Four AFSs were selected in each local government area (LGA) - this consisted majorly of smallholder farmer’s farm with silvoarable systems in the region (4 communities per LGA, total of 20 communities). The selection criteria for AFS was based on farm size not less than 1 hectare. The results from the analysis revealed that highest soil carbon stock [C stock (Mg Cha-1)] was recorded from AFSs in Dekina (334.43 Mg Cha-1) while no significant difference in carbon stock was observed from the soils of AFSs in Ankpa, Ofu, Olamaboro, and Omala LGAs (69.01, 159.21, 142.58, 117.33 Mg Cha-1 respectively). Nonetheless, the soils from AFSs in Dekina LGA had highest CO2 emissions followed by Ofu LGA (186.23 and 159.40 gCO2 emitted/50g wet soil slice respectively) while the lowest CO2 emissions (104.15 and 88.88 gCO2 emitted/50g wet soil slice) were recorded from Ankpa and Omala LGAs respectively. The highest carbon sequestration recorded from soils of AFSs in Dekina LGA may depend on the soil C input and soil stabilization processes including tree species and density and again highest CO2 emissions from the same Dekina LGA can be attributed to the coarse texture of the soils as coarse soils are considerably more susceptible to releasing their carbon. On the other hand, the absence of variation in CO2 emission levels in some of the locations studied can be attributed to similar land management practices like tillage, bush burning and soil fertility management.