Soil ammonia-oxidizing archaea in a paddy field with different irrigation and fertilization managements

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 edaphic drivers in paddy soils under different fertilization and irrigation regimes remain unclear. In this study, we investigated AOA abundance, diversity and activity in acid paddy soils by a 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 T₂ (optimal irrigation and fertilization)-treated soils, whereas the lowest PAO (0.004 μg NO ₂ ^-  -N g^-1 d.w.day^-1) in T₀ (traditional irrigation)- treated soils. Compared with the T₀-treated soil, the T₂ 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 T₂-treated soil than those in the T₁ (traditional irrigation and fertilization)- treated soil. In addition, these two edaphic factors further influenced the AOA community composition. The AOA phylum Crenarchaeota was mainly found in the T₂-treated soils. Phylogenetic analysis revealed that most of the identified OTUs of AOA were mainly affiliated with Crenarchaeota. Furthermore, the T₂ treatment had higher rice yield than the T₀ and T₁ treatments. Together, our findings confirm that T₂ might ameliorate soil chemical properties, regulate the AOA community structure, increase the AOA abundance, enhance PAO and consequently maintain rice yields in the present study.