Effects of drip irrigation on bacterial diversity and community structure in rhizosphere soil of alfalfa

Abstract:

[Background] As an important group of soil microorganisms, bacteria can effectively promote the material cycle and energy flow of soil. Bacterial diversity and community structure can reflect the quality of soil. High-throughput sequencing has been widely used in studying soil microorganisms, and can get the classification information of soil bacteria more conveniently and accurately than traditional sequencing technology. [Objective] To analyze the bacterial diversity in alfalfa soil of drip irrigation as well as to study the relationship between the bacterial diversity and environmental factors. [Methods] High-throughput sequencing on PCR-ampllified 16S rRNA gene V3?V4 fragments was used to determine the bacterial diversity in rhizosphere and non-rhizosphere soils of alfalfa under two growth patterns, and were analyzed and compared. [Results] The richness of bacterial communities calculated by the Chao1 index and the bacterial community diversity calculated by the Shannon index showed the same trend: drip irrigation alfalfa soil>natural rainfall alfalfa soil; 879 675 high-quality sequence were derived, 4 431 operational taxonomic units (OTUs) from 4 groups of soil samples, which were classified into 46 categories, 53 classes, 116 orders, 220 families and 469 genera, except some unidentified bacteria. Proteobacteria (25.27%?34.42%) was the dominant phylum, of which Alphaproteobacteria (11.41%?18.97%) was the dominant subgroup and Sphingomonas (1%?4.54%) was the dominant genus. Compared with natural rainfall, the community structure of 6 phylum and 16 genus of rhizosphere soil bacteria under drip irrigation changed significantly. In addition, RDA analysis showed that different environmental factors had different effects on the microbial community. The abundance of 9 bacteria genera in the rhizosphere soil of drip irrigation was positively correlated with total phosphorus, available phosphorus, available nitrogen, total potassium, organic matter, soild-neutral phosphatase and soild-urease contents. [Conclusion] As a new water-saving technology, drip irrigation increases the diversity and abundance of bacteria in rhizosphere soil of plants on the basis of promoting plant growth, increasing yield and saving cost. The results provide scientific data for the reform of new irrigation systems and the development and utilization of soil microbial resources.