Nitrogen and phosphorus co-limit mineralization of labile carbon in deep subsoil

摘要

The growth of deep-rooted crops has the potential to increase carbon deposition within deep subsoil layers, thereby contributing to climate change mitigation. Yet, the mechanisms of labile carbon stabilization in deep subsoils remain uncertain. Here we studied the effect of nitrogen, phosphorus and sulphur limitations on the microbial mineralization of added glucose and an artificial root exudate mixture (both spiked with C-14-glucose) in intact soil samples from a deep subsoil (5-6 m) over a 10-week incubation period, where the temporal respiration of CO2 and (CO2)-C-14 were quantified. We found that mineralization was co-limited by nitrogen and phosphorus, but the cumulative amount of CO2 emitted was significantly larger from artificial root exudates than glucose, suggesting that the nitrogen carried in amino acids in root exudates (here, L-arginine) was sufficient to overcome the nitrogen limitation in this subsoil.