Nitrification driven by bacteria and not archaea in nitrogen-rich grassland soils

Abstract

The oxidation of ammonia to nitrate, nitrification, is a key process in the nitrogen cycle. Ammonia-oxidizing archaea are present in large numbers in the ocean and soils, suggesting a potential role for archaea, in addition to bacteria, in the global nitrogen cycle. However, the importance of archaea to nitrification in agricultural soils is not well understood. Here, we examine the contribution of ammonia-oxidizing archaea and bacteria to nitrification in six grassland soils in New Zealand using a quantitative polymerase chain reaction. We show that although ammonia-oxidizing archaea are present in large numbers in these soils, neither their abundance nor their activity increased with the a..