Aggregate stability affects carbon sequestration potential of different tropical soils

Abstract

Aggregate stability and carbon (C) sequestration in soils are closely related phenomena. However, high aggregate stability does not always ensure high carbon sequestration to some soil types since other binding agents could dominate other than carbon. Thus, this study aimed to determine the relationship between aggregate stability and carbon sequestration of different tropical soils which basically differ in geology, genesis, and possibly in their dominant aggregating agents. The study selected four representative soil types (Haplic Acrisol, Calcaric Cambisol, Silic Andosol and Haplic Ferralsol) found in Leyte and Samar that were characterized by previous workers. Soil Organic Carbon (SOC) and Aggregate Stability (AS) in dry and wet conditions were quantified using standard procedures. Some pertinent secondary data were also recorded as reference for each soil type. Results revealed that only Silic Andosol showed positive significant correlation (0.93) between aggregate stability and soil organic carbon (SOC). The other soil types showed weak and negative correlation between aggregate stability and SOC; however, their stability revealed a strong positive relationship with inorganic binding agents. Therefore, each soil type reflects a different relationship between aggregate stability in wet condition and SOC and that the variations could be attributed to the differences in the morpho-physical and geochemical nature of the soils. Moreover, SOC is found to greatly influence the aggregate stability in Silic Andosol, thus the soil carbon sequestration potential of this soil type is generally related to its aggregate stability. However, in other soil types like Haplic Acrisol, Calcaric Cambisol, and Haplic Ferralsol, other binding agents like Calcium (Ca) and iron oxides dominate and control the formation and stability of aggregates rather than SOC.