Effect of Water Deficiency on the Rhizosphere Microenvironment of Sunflower under Film Drip Irrigation

Abstract

【Objective】 This field experiment of drip irrigation under sunflower film was carried out in the Hailiutu Science and Technology Park of Inner Mongolia Agricultural University, in order to explore the effects of water deficit on the microbial diversity, community structure and metabolic function of sunflower rhizosphere soil. 【Method】 Sunflower was irrigated with 900 m3/hm2 of saline before planting, and drip irrigation under film was used throughout the growth period. The control treatment, W1(450 m3/hm2 in the squaring stage and 450 m3/hm2 during the reproductive growth stage), involved sunflowers under mulch drip irrigation with a water deficit. Two water deficit treatments were implemented during the squaring stage: W2 (300 m3/hm2 irrigation during the squaring stage, 450 m3/hm2 irrigation during the reproductive growth stage), W3 (150 m3/hm2 irrigation during the squaring stage, 450 m3/hm2 irrigation during the reproductive growth stage).During the reproductive growth period, mild and severe water deficits were treated using two strategies: W4 (450 m3/hm2 irrigation during the squaring stage, and 225 m3/hm2 irrigation during the reproductive growth period), and W5(450 m3/hm2 irrigation during squaring stage, with no irrigation during the reproductive growth period).The Illumina high-throughput sequencing technology was utilized to analyze the structure, function, and diversity of the soil microbial community in the rhizosphere. Additionally, the study examined the impact of water deficit on soil physicochemical properties, as well as on the structure and function of the microbial community. 【Result】 At the squaring stage, W2 and W3 treatments significantly increased the electrical conductivity (EC), ammonium nitrogen (NH4+-N) content, and temperature (T) of rhizosphere soil compared to W1.Moreover, this water deficit also decreased the soil water content (SWC), EC and pH value of the mature rhizosphere soil. At the mature stage, W2 treatment boosted the richness index(Chao1), evenness index(Pielou), and diversity index(Shannon) of rhizosphere soil bacteria and fungi. In the four water deficit treatments, the relative abundance of Proteobacteria under W2 treatment was significantly reduced by 7.66% compared with W1. The relative abundance of Chloroflexi and Ascomycota increased significantly by 32.19% and 5.25%, respectively, under W3 treatment compared to W1. The application of W4 and W5 treatments led to an increase in the relative abundance of Actinomycetes, Acidobacterium, and Mortierella. The correlation between bacterial community and soil physicochemical properties was stronger than that of the fungal community. Bacteria showed a positive correlation with EC, ammonium nitrogen, and nitrate nitrogen in the rhizosphere soil. On the other hand, bacteria had a negative correlation with soil moisture content (SWC) and pH value. Biosynthesis is the dominant metabolic function of bacteria and fungi in rhizosphere soils. The main factor affecting dominant metabolic function of bacteria is SWC. In addition, EC, ammonium nitrogen, and nitrate nitrogen will have a positive impact on dominant metabolic function of bacteria. 【Conclusion】 In summary, The water deficit at the squaring stage improved the physicochemical properties of rhizosphere soil compared with the water deficit in the reproductive growth stage. Additionally, the mild water deficit at the squaring stage improved the structure, diversity, and metabolic function of the rhizosphere soil microbial community, thereby making it a suitable water treatment for the growth of rhizosphere microorganisms.

Keywords

• drip irrigation under film
• water deficiency
• microbial community
• metabolic function
• high-throughput sequencing