Ammonia-oxidizing archaea and bacteria responding differently to fertilizer type and irrigation frequency as revealed by Illumina Miseq sequencing

Abstract

Ammonia oxidation, the first and rate-limiting step of nitrification, can be strongly influenced by agricultural practices, but little is known about the effects of fertilization and irrigation combination on ammonia oxidizers in agricultural soils. This study was designed to reveal how fertilizer type and irrigation frequency affect the ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities in a northern Chinese wheat-maize rotation soil. Soil samples were collected from a long-term field experiment under different fertilization and irrigation regimes located in Wuqiao Experimental Station of China Agricultural University in June 2016. The abundance, diversity, and composition of AOA and AOB in the soils were investigated by using real-time PCR and Illumina Miseq sequencing approaches. The abundance of AOA was higher in the irrigated treatments, but lower in the treatments without irrigation, than that of AOB. The AOA abundance was positively correlated with soil moisture, pH, and NO3 −-N, while the AOB abundance was positively correlated with TN and NO3 −-N. Soil potential nitrification activity (PNA) was significantly positively correlated with the AOB abundance. Both fertilizer type and irrigation frequency significantly affected Shannon, ACE, and Chao1 indices of the AOB community, while only irrigation frequency had a significant impact on Shannon index of the AOA community. PCoA analysis results indicated that irrigation frequency greatly affected the AOA community structure, while fertilizer type played a more important role in affecting the AOB community structure. Mantel test and correlation heatmap analysis results indicated that soil moisture, pH, and NH4 +-N were significantly correlated to the AOA community structure, and TN and SOC were significantly correlated to the AOB community structure. This study demonstrated that irrigation frequency greatly influenced the AOA community, while fertilizer type had a stronger effect on the AOB community. It was AOB but not AOA played a more important role in soil nitrification. Moreover, soil moisture, pH, and TN were the main determinants in driving the AOA community and TN and SOC were the main factors in influencing the AOB community.