Increased soil nitrogen supply enhances root-derived available soil carbon leading to reduced potential nitrification activity

Summary

Nitrogen (N) immobilisation by heterotrophic microorganisms is critical for reducing N losses from soils and ensuring a long-term supply of N to plants in grassland ecosystems. The supply of carbon (C) available to soil microbes may stimulate heterotrophic N immobilisation by reducing the availability of ammonium to autotrophic nitrifiers and, hence, for nitrification activity. The main source of available C to soils is rhizodeposition, but its effects on nitrification activity remain unclear as rhizodeposition differs between plant species and varying N availabilities. The aim of this work was to investigate the role of root-derived C on nitrification activity for five different grassland plant species. Cichorium intybus (chicory), Lolium perenne (perennial ryegrass), Plantago lanceolata