Inorganic and organic carbon dynamics in a limed acid soil are mediated by plants

Abstract

Lime is commonly used to overcome soil acidification in agricultural production systems; however, its impact on inorganic and organic soil carbon dynamics remains largely unknown. In a column experiment, we monitored rhizosphere effects on lime dissolution, CO2 effluxes, and the concentrations of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in leachate from an acidic Kandosol. The experiment consisted of four treatments viz: soil only (control), soil + lime, soil + wheat, and soil + lime + wheat. We measured CO2-C effluxes at 7, 43 and 98 days after planting (DAP) and leachate was collected at 56 and 101 DAP. The soil CO2-C efflux rate increased significantly with lime addition at 7 and 43 DAP compared to control. At 43 DAP, the largest increase in CO2-C effluxes was observed in the lime + wheat treatment. However, at 98 DAP similar CO2-C effluxes were observed from wheat and lime + wheat treatments, suggesting that most of the lime was dissolved in the lime + wheat treatment. Both DOC and DIC concentrations in the leachate increased significantly with lime and wheat only treatments (cf. control). In contrast to DOC, there was an increase in the DIC concentration in the soil leachate from lime + wheat treatment columns at 101 DAP (significant wheat × lime interaction), thus, accentuating the pronounced role of wheat roots. We conclude that plant mediated dissolution of lime increased the concentration of DIC in the soil leachate, while both liming and presence of plants enhanced DOC leaching.