Effects of potassium fulvic acid and potassium humate on microbial biodiversity in bulk soil and rhizosphere soil of Panax ginseng.

Abstract Potassium fulvic acid (BSFA) and potassium humate (KHM), as organic fertilizers, can improve soil structure, increase soil nutrient levels and prevent plant diseases. However, knowledge is limited regarding how BSFA and KHM influence soil microbial communities and the interrelationships between community members associated with Panax ginseng. Soil pH and nutrient content increased significantly as a result of the addition of BSFA and KHM. The pH, NH4+-N, NO3−-N, AP and AK increased by 1.72 %–5.55 %, 70.09 %–108.39 %, 35.38 %–216.20 %, 1.21 %–14.19 % and 3.40 %–5.94 %, respectively, in the BSFA and KHM treatments. The soil nutrient increase may be related to Micrococcaceae and arbuscular mycorrhizal fungi (AMF). The structure of the microbial community also changed radically from that of the control group, and Chloroflexi (2.69 %–3.15 %), Actinobacteria (4.33 %–7.53 %) and Acidobacteria (9.44 %–11.62 %) were the dominant microorganisms at the phylum level in bacteria. In contrast, the dominant fungi at the phylum level were Ascomycota (77.39 %–78.08 %), Glomeromycota (0.36 %–2.68), Olpidiomycota (0.02 %–3.78 %) and Basidiomycota (0.80 %–1.17 %). Fusarium oxysporum and Ascomycota were biomarkers for BSFA and KHM, which may be related to pathogenic bacteria. Network analysis revealed that the association among members of the soil microbial community was more positive than negative following application of KHM, and more positive (62.5 %) than negative (37.5 %) correlations were observed between bacteria, whereas the fungal community exhibited more positive (97.3 %) than negative (2.7 %) correlations. PICRUST predicted the microbial function of adding KHM and BSFA to the soil, and these pathways mainly belong to the degradation and metabolism of organic matter, saprophytic organisms and plant pathogens. In summary, our study demonstrated that the addition of BSFA and KHM increased the nutrients in the ginseng soil and reshaped the microbial function in soils, providing a theoretical foundation for soil improvement and biological control of ginseng diseases. However, due to the limitations of greenhouse cultivation, additional long-term experiments on farmland with different climate changes are recommended.