Organic carbon associated with tillage-induced aggregates of some quartz-dominated loamy soils in a semi-arid region of South Africa

Abstract

Tillage breaks down soil aggregates exposing the associated organic matter to increased degradation. The extent of degradation depends on the soil properties, mainly texture and mineralogy. The objective of this study was to determine the amount of soil organic carbon (SOC) in various aggregates under conventionally tilled and no-till systems in some quartz-rich loamy soils in South Africa. The aggregate-associated SOC was significantly (p < 0.001) influenced by tillage systems. The amount of aggregate-associated SOC was 1.67 times higher in tilled than no-till soils because of the crop residue that was incorporated annually during tillage. In the untilled soil, vegetation was grazed by cattle, depriving the soil of fresh organic matter input. Quartz mineralogy and the semi-arid climate were generally responsible for the low SOC content in both tillage systems. It was concluded that aggregate-associated SOC content increased in the loamy tilled soils relative to no-till soils because of the incorporated crop residue.