Tillage, not fertilization, dominantly influences ammonia-oxidizing archaea diversity in long-term, continuous maize

Abstract

Ammonia-oxidizing archaea (AOA) catalyze a rate-limiting step in nitrification - ammonia (NH3) oxidation. There are more AOA than ammonia-oxidizing bacteria (AOB) in many soil systems, including cropland, and AOA dominate in unfavorable environmental conditions, such as soils with low NH4-N. The ecological role of the ubiquitously distributed AOA is unclear, as are the factors regulating AOA community dynamics. This study investigated how long-term N fertilization and tillage management influenced the AOA community in cropland. The study site was a long-term (>40 years) field experiment with either no-tillage (NT) or plow tillage (PT) at three N fertilizer rates (0, 168, and 336 kg ha−1) and continuous maize (Zea mays L.). We used PCR-denaturing gradient gel electrophoresis (DGGE) to assess the archaeal amoA gene as a measure of the changing AOA community. Tillage rather than N fertilizer played the dominant role affecting the AOA community. Fertilizer rate did not significantly influence AOA diversity, but sample season and N fertilization had selection function on AOA composition. In winter, AOA were more diverse in NT than PT. Unique groups were discovered in different treatments, demonstrating selection by tillage, fertilization, season, and/or their interactions. The significant tillage regulation of AOA provides new clues to investigate which environmental factors influence the AOA community and to explore its ecological significance in agricultural land.