This study investigated the contribution of different nitrifier groups (ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), complete ammonia-oxidizing (comammox) bacteria, and nitrite-oxidizing bacteria (NOB)) to nitrogen cycling in a highly fertile agricultural soil. Results showed that AOA strongly dominated net nitrification activities, outnumbering AOB and comammox by 50- to 430-fold, with low N₂O yields. Nitrification rates were similar in plant-covered and fallow plots, and mass balance calculations indicated that plants primarily used nitrate, not ammonium. The findings highlight the integral role of AOA in nitrogen cycling in fertile agricultural soils.

Laibin Huang, Seemanti Chakrabarti, Jennifer Cooper, Ana Perez, Sophia M. John, Samira H. Daroub, Willm Martens-Habbena