Shifts of the soil microbiome composition induced by plant-plant interactions under increasing cover crop densities and diversities

Authors: NEWBERGER, DEREK - Colorado State University; MINAS, IOANNIS - Colorado State University; Manter, Daniel; VIVANCO, JORGE - Colorado State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2023
Publication Date: 10/10/2023
Citation: Newberger, D.R., Minas, I.S., Manter, D.K., Vivanco, J.M. 2023. Shifts of the soil microbiome composition induced by plant-plant interactions under increasing cover crop densities and diversities. Scientific Reports. 13. Article 17150. https://doi.org/10.1038/s41598-023-44104-8.
DOI: https://doi.org/10.1038/s41598-023-44104-8

Interpretive Summary: Increasing the total crop biomass may be beneficial for not only forage, but also other ecosystem benefits such as weed suppression and carbon sequestration. One potential way to increase total biomass is to increase planting density; however, this may lead to smaller individual plants due to competition. This work aimed to identify shifts in bacterial abundance and richness that can help alleviate plant competition and promote the use of higher planting densities for maximum total crop and individual plant biomass.

Technical Abstract: Interspecific and intraspecific competition and facilitation have been a focus of study in plant-plant interactions. Plants recruit specific beneficial microbes based on their environment, but the effect of how competition or facilitation of neighboring plants influence the plant recruitment of soil microbes is understudied. In a greenhouse microcosm experiment, three cover crops (alfalfa, brassica, and fescue) were grown alone, in paired mixtures, or altogether under different densities. Total pot biomass increased as density increased for all monoculture trials. Monoculture plantings of brassica were associated with Azospirillum spp., Fescue with Ensifer adhaerens, and alfalfa with both bacterial taxa. Azospirillum spp. and Ensifer adhaerens has been previously identified as free-living nitrogen fixers. In the polycultures of cover crops, total above ground biomass for alfalfa increased with density for all plant mixtures. Total above ground biomass for brassica remained unchanged across all plant mixtures. Fescue total above ground biomass was variable, with low biomass in brassica mixtures. Differential microbial abundances correlated with a different combination of bacterial taxa for each plant mixture, however, within each plant mixture abundancis of the same bacteria often increased with an increase in plant density. Three plant mixtures showed abundance shifts of bacteria such as Planctomyces sp. SH-PL14 and Sandaracinus amylolyticus. Facilitation was best supported for the alfalfa-fescue interaction as the total above ground biomass was the highest of any mixture. Additionally, the bulk soil microbiome that correlated with increasing plant densities showed increases of previously known plant growth promoting rhizobacterium such as Achromobacter xylosoxidans, Stentotrophomonas spp., and Azospirillum sp. In contrast, Agrobacterium tumefaciens, a previously known generalist phytopathogen also increased with alfalfa-fescue plant densities. This could suggest a strategy by which after facilitation one of those plants could culture a pathogen that could be more detrimental to the other one.