Abstract: 【Objective】This study was carried out to investigate the bacterial community in a wheat-maize rotation field during wheat growing season in northern China. The effects of long-term different fertilization and irrigation regimes on the abundance, diversity and composition of bacterial community were identified. It will provide evidences for further optimizing fertilization and irrigation managements, improving soil productivity, and maintaining soil microbial diversity.【Method】Based on a long-term fertilization and irrigation experiment carried out in Wuqiao Experimental Station of China Agricultural University, six different soil samples were collected after wheat was harvested, including chemical fertilization and no irrigation (CI0), chemical fertilization and irrigation at the jointing stage (CI1), chemical fertilization and irrigation at the jointing and filling stages (CI2), manure fertilization and no irrigation (MI0), manure fertilization and irrigation at the jointing stage (MI1), and manure fertilization and irrigation at the jointing and filling stages (MI2). The abundance, diversity and composition of the bacteria community in different soil samples were revealed by using real-time PCR and Illumina Miseq sequencing platform, targeting the 16S rRNA gene. Correlation analysis was carried out between soil properties and the bacteria community abundance, diversity and structure.【Result】Irrigation significantly increased soil moisture and soil pH, and manure fertilization significantly increased Total Organic Carbon (TOC) content compared with no irrigation and chemical fertilization treatments, respectively. The bacterial 16S rRNA gene copy numbers ranged from 4.34×10⁹ to 1.39×10¹⁰ g^-1 d.w.s in different treatments. Irrigation significantly increased the bacterial 16S rRNA gene copy number by 1.17-1.60 and 0.76-1.93 times in the chemical and manure fertilization treatments, respectively. The bacterial α diversity index results showed that irrigation but not fertilization significantly affected bacterial α diversity index. At the phylum level, thirty-nine phyla were obtained in all the treatments, among which Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria and Bacteroidetes were the predominant phyla, accounting for 77.22%-86.28% of the total reads. There were significant variations in relative abundance of Actinobacteria【Conclusion】Irrigation greatly altered the abundance, diversity, and structure of the bacterial community, while fertilization had a minor effect on the abundance and structure of the bacterial community, and soil moisture and soil pH were the potential environmental factors associated with the bacterial community variations. (11.09%-27.01%), Bacteroidetes (5.45%-12.13%) and Saccharibacteria (2.41%-3.77%) among different treatments. Irrigation significantly decreased the relative abundance of Actinobacteria and Saccharibacteria by 36.48%-48.03%, 22.17%-33.67% and 15.21%-45.54%, 13.40%-23.97% in the chemical and manure fertilization treatments, respectively. Hierarchical clustering and principal component analysis (PCA) results showed that both fertilization and irrigation managements affect the bacterial structure, and irrigation had a stronger effect than fertilization on the bacterial structure. In addition, there were significant correlations between soil moisture, soil pH, Total Nitrogen (TN) content, and TOC content and the abundance, α diversity index and structure of the bacterial community.

Key words: manure fertilizer, irrigation, bacterial community diversity, high-throughput sequencing, northern China