Effects of Dripping Rate with Reclaimed Water on Typical Microbial Community Structure in the Root Zone Soil of Tomato

Abstract

【Background and objective】 Rhizosphere is the interface of soil and plant housing a unique microbial community which not only mediates carbon and nutrient cycles but is also the underlying drivers of soil structure genesis. Soil microorganisms self-restructure following environmental change, which has a consequence for all biogeochemical processes. The purpose of this study is to investigate if and how dripping rate affects the microbial community of the rhizosphere of tomato drip-irrigated using reclaimed water. 【Method】 Pot experiment was conducted in an intelligent artificial climate chamber. It compared three dripping rates: 2, 4 and 8 L/h, with traditional flood irrigation taken as the control. After harvesting the plants, microbial community in the different root zone soil layers (0~5, 5~10, and 10~15 cm) of each treatment was analyzed using the 16S rDNA microbial diversity sequencing method. 【Result】 Microbial diversity index under drip irrigation was higher than that under the control, regardless of the dripping rate, and their difference was most significant in the 5~10 cm soil layer (P<0.05). Dripping rate did not show a significant impact on dominant flora at phylum and genus level, but the relative abundance of microbial community changed with edaphic factors such as pH, EC, total phosphorus. Dripping at the rate of 2 L/h increased the total phosphorus content in the 10~15 cm soil compared with other treatments, and it also significantly increased the relative abundance of Bacteroidetes. Compared with the control, the drip irrigations increased pH and reduced the relative abundance of Sphingomonas in the 10~15 cm soil. When the dripping rate was 2 L/h, the abundance of each functional microbial pathway was the highest in the top 0~5 cm soil. 【Conclusion】 Dripping rate in using reclaimed water to irrigate tomato altered the physical and chemical properties of soil, thereby shifting microbial community and microbial distribution in the rhizosphere. It also reshaped the distribution of the abundance of some functional flora in soil profile. Our finding implicates that selecting an appropriate drip irrigation rate could have a significant consequence for carbon and nutrient cycles in drip-irrigated crops using reclaimed water due to its impact on microbial community and the associated functions.

Keywords

• reclaimed water irrigation
• drip irrigation
• dripping rate
• root soil
• microbial community