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

Nitrogen (N) immobilisation by heterotrophic microorganisms is critical for reducing N losses from soils and ensuring a long-term supply of to plants in grassland ecosystems. The carbon (C) available soil microbes may stimulate the availability ammonium autotrophic nitrifiers and, hence, nitrification activity. main source C rhizodeposition, but its effects on activity remain unclear as rhizodeposition differs between plant species varying availabilities. aim this work was investigate role root-derived five different species. Cichorium intybus (chicory), Lolium perenne (perennial ryegrass), Plantago lanceolata (ribwort plantain), Raphanus raphanistrum R. sativus (wild cultivated radish), an unplanted control were grown nine weeks under controlled environmental conditions treated either with low (no urea-N) or high rate additional (550 kg urea-N ha?1). Plant biomass, water-extractable concentration ammonia-oxidising bacteria (AOB) abundance increased planted treatments. addition resulted microbial led decreased potential compared those An increase associated decrease activity, suggesting that have stimulated NH4+ uptake thus immobilisation. This study highlights can be used manipulate tight coupling cycling processes, identify management practices will promote retention reduce soils.