Archaea Are the Major Responsive Ammonia Oxidizers in a Paddy Soil Following Fertilization and Irrigation

Because ammonia-oxidizing archaea (AOA) are ubiquitous and highly abundant in almost all terrestrial soils, they play an important role in soil nitrification. However, the changes in the structure and function of AOA communities and their specific environmental drivers in paddy soils under different fertilization and irrigation regimes remains unclear. In this study, we investigated archaeal abundance, activity and community composition in acid paddy soils by a 10-year field experiment. Results indicated that the highest potential ammonia oxidation (PAO) (0.011 µg NO 2 − -N g − 1 d.w.day − 1 ) was found in T 2 (optimal irrigation and fertilization) - treated soils, whereas the lowest PAO (0.004 µg NO 2 − -N g − 1 d.w.day − 1 ) in T 0 (traditional irrigation)- treated soils. Compared with the T 0 - treated soil, the T 2 treatment significantly ( P  < 0.05) increased AOA abundances. Furthermore, the abundance of AOA was significantly ( P  < 0.01) positively correlated with pH, soil organic carbon (SOC), and PAO. Meanwhile, pH and SOC content were significantly ( P  < 0.05) higher in the T 2 - treated soil than those in the T 1 (traditional irrigation and fertilization)- treated soil. In addition, these two edaphic factors further influenced the AOA community composition. The archaeal phylum Crenarchaeota and genus Candidatus Nitrosotalea were mainly found in the T 2 -treated soils. Phylogenetic analysis revealed that most of the identified OTUs of AOA were mainly affiliated with Crenarchaeota . Together, our findings confirmed that T 2 might ameliorate soil chemical properties, regulate the AOA community structure, increase the AOA abundance, enhance PAO and consequently maintain optimum rice yields in a subtropical paddy field.