[Effect of cropping patterns onbacterial community diversity and metabolic function in rhizosphere soil of Angelica...

The sustainable development of Angelica sinensis industry is seriously restricted by continuous cropping obstacles. In order to explore an efficient cultivation technique for A. sinensis, an experiment with five cropping patterns [A: Pisum sativum (Ps)-A. sinensis (As)-As, control); B: Ps-Triticum aestivum (Ta)-As; C: Ps-Mongolia astragalus (Ma)-As; D: Ps-Solanum tuberosum (St)-As); E: Ps-Fallow (F)-As)] were conducted in major A. sinensis producing areas located in Weiyuan County, Gansu Province. The physicochemical properties and relative abundance of bacterial genomic DNA in rhizosphere soil under different cropping patterns were measured during A. sinensis harvest period to investigate the effects of different cropping patterns on physicochemical properties, bacterial community diversity, and metabolic pathways. The results showed that: 1) the physicochemical properties in A. sinensis rhizosphere soil varied among different cropping patterns. Compared with the control, soil electrical conductivity under C pattern was significantly higher, and lower under B, D and E, CO₂ respiration rate for B, C, D and E were significantly increased. 2) Soil bacteria of A. sinensis rhizosphere soil in the five cropping patterns belonged to 26 phyla and 368 genera. The dominant genera were Gemmatimonas from Gemmatimonadetes, Sphingomonas from Proteobacteria, and Subgroup_6 from Acidobacteria. Compared with the control, the relative abundance of Proteobacteria and Actinobacteria under B and C patterns was significantly higher, Acidobacteria in D pattern was significantly lower, while Proteobacteria, Acidobacteria, and Actinobacteria in E pattern was significantly higher. 3) There were significantly negative relations between soil pH, electrical conductivity, contents of organic matter, available nitrogen, phosphorus and potassium with the relative abundance of Proteobacteria in A. sinensis rhizosphere soil across the five cropping patterns. 4) There was significant difference in relative abundance for bacteria of six metabolic pathways under the five cropping patterns. In conclusion, C pattern had a regulating effect on physicochemical properties and bacterial communities in A.sinensis rhizosphere soil, which could be taken as a major practice to overcome the continuous cropping obstacles.