Soil Carbon Sequestration in Sorghum Cropping Systems: Evidence From Stable Isotopes and Aggregate-Size Fractionation

Abstract

Abstract: Management practices can influence both the quantity of soil organic carbon (SOC) and its distribution into different fractions or pools. We investigated SOC sequestration potentials of cropping systems in nearsurface (0-5 cm) samples through soil size and density fractionation coupled with acid hydrolysis and natural abundance of stable isotopes (δ C values for soils from SWSoy varied from −20‰ to −22‰, reflecting a mixed input from C 3 -derived and C 4 -derived residue input. For whole soil and all aggregate-size fractions, SOC concentrations were significantly higher for NT than conventional tillage. However, the effects of cropping system and N fertilization on SOC interacted with tillage. Greater SOC for enhanced cropping (SWSoy) or N fertilization was observed only under NT. The fraction of <53 μm represented a greater proportion of soil than other aggregate-size fractions. Our long-term study indicated that SOC and its various fractions, including more resistant, can be increased by NT with enhanced cropping and N fertilization