Impact of Aggregate Size on Soil Carbon Sequestration and Aggregate Stability

Soil aggregation is an important process in carbon sequestration and therefore a useful strategy to mitigate the increase in the concentration of atmospheric CO2. The study was, carried out on an Acrisol at the KNUST Cocoa (Theobroma cacao) plantation. Samples, covered with deep litter, shallow litter and no litter were taken from the 0 - 15 cm depth from three different locations at the sampling site. The organic carbon content and aggregate stability were determined on air - dried samples sieved through graduated sieves into sizes of 0.5 - 1.0 mm, 1.0 - 2.0 mm, 2.0 - 4.0 mm and 4.0 - 6.0 mm using the loss- on- ignition method and modified wet-sieving method, respectively. The study showed that SOC sequestered was highest in the deep litter and the aggregate sizes of 4.0 - 6.0 mm at all sites. The weighted mean of organic carbon for all sizes were 3.02% for deep litter, 2.84% for shallow litter and 1.55% for no litter spots, respectively. The aggregate sizes of 4.0 - 6.0 mm also had the highest stability to external forces. There was also a positive correlation between SOC and aggregate stability. The study confirmed that mature cocoa farms have the potential to store more organic carbon and are relatively stable to reduce erosion and enhance root penetration.