The impact of long-term liming on soil organic carbon and aggregate stability in low-input acid soils

摘要

This study used two field trials with 5 and 34 years of liming histories, respectively, and aimed to elucidate the long-term effect of liming on soil organic C (SOC) in acid soils. It was hypothesized that long-term liming would increase SOC concentration, macro-aggregate stability and SOC concentration within aggregates. Surface soils (0-10 cm) were sampled and separated into four aggregate-size classes: large macro-aggregates (> 2 mm), small macro-aggregates (0.25-2 mm), micro-aggregates (0.053-0.25 mm) and silt and clay fraction ( 0.053 mm) by wet sieving, and the SOC concentration of each aggregate-size was quantified. Liming decreased SOC in the bulk soil and in aggregates as well as macro-aggregate stability in the low-input and cultivated 34-year-old trial. In contrast, liming did not significantly change the concentration of SOC in the bulk soil or in aggregates but improved macro-aggregate stability in the 5-year-old trial under undisturbed unimproved pastures. Furthermore, the single application of lime to the surface soil increased pH in both topsoil (0-10 cm) and subsurface soil (10-20 cm) and increased K2SO4-extractable C, microbial biomass C (C-mic) and basal respiration (CO2) in both soil layers of both lime trials. Liming increased the percentage of SOC present as microbial biomass C (C-mic/C-org) and decreased the respiration rate per unit biomass (qCO(2)). The study concludes that despite long-term liming decreased total SOC in the low-input systems, it increased labile C pools and the percentage of SOC present as microbial biomass C.