Agroforestry system: Polygonatum odoratum and Vernicia fordii intercropping effects on crop quality, soil nutrients and microbial community structure

Abstract

Vernicia fordii, a tropical and subtropical oil tree species, is highly esteemed for its fruit but yields slow economic returns. To address this, a study was conducted on intercropping Vernicia fordii with Polygonatum odoratum, a Chinese herbal medicine, to investigate its effects on rhizosphere soil microorganisms and potential for accelerated economic gains. Comparisons were drawn with monocultures of both P. odoratum and V. fordii. Utilizing 16S rDNA sequencing analysis, the study unveiled a profound impact of intercropping on the rhizosphere soil microbial community. Specifically, the abundance of certain bacterial communities such as Actinomycetes, Bacteroidetes, and Chloroflexi, as well as fungal communities like Ascomycota and Basidiomycota, underwent significant changes under intercropping conditions. Within the bacterial community, the relative abundance of Actinobacteria, Myxococcola, and Chloroflexi increased notably by approximately 33.3%, 50%, and 50%, respectively, while Proteobacteria and Acidobacteria decreased significantly by 16.7% and 20%, respectively (p < 0.05). Concurrently, Ascomycota and Basidiomycota in the fungal community showed a significant increase in relative abundance by 10% and 5%, respectively. Functional predictions further indicated enhanced metabolic activities related to nitrogen fixation and chitin decomposition.Moreover, intercropping led to a marked increase in soil nutrient content, including organic matter, available potassium, alkaline hydrolyzable nitrogen, and sucrase activity, which are crucial for the advancement of biogeochemical processes. In terms of plant growth, P. odoratum under intercropping exhibited significant advantages, with increased plant height, ground diameter, and biomass. Notably, the ground diameter increased by 9.75% and biomass by 28.8%. Additionally, the chemical composition of P. odoratum underwent changes, with polysaccharides, total flavonoids, and total saponins showing increases of 1%, 32.9%, and 13.9%, respectively, whereas total phenolic content decreased by 19.0% (p < 0.05). In summary, intercropping not only alters the composition and abundance of soil microbial communities and enhances soil nutrient content but also promotes the growth and accumulation of specific chemical components in P. odoratum. These findings have positive implications for agricultural and forestry production, offering valuable insights for improving agricultural efficiency and economic benefits.