Sorghum growth and development in soils from different switchgrass fields is altered by the presence of an intact soil microbial community

Katie Grantham, Karen A. Stahlheber, and Katherine L. Gross
Kellogg Biological Station, Michigan State University

Presented at the All Scientist Meeting (2015-04-15 to 2015-04-16 )

Switchgrass (Panicum virgatum) is a popular candidate biofuel in the USA, however, little is known about its relationship with belowground microbial communities. This includes the relationships between switchgrass and arbuscular mycorrhizae (AMF), fungi that live symbiotically with plant roots. Biofuel crops are commonly fertilized, yet the potential for changes in microbial communities following fertilization and the effect of this on plant performance is not well understood. We grew sweet sorghum (Sorghum bicolor) in the greenhouse and inoculated plants with soil from fertilized and unfertilized fields of ‘Cave-in-Rock’ and ‘Southlow’ switchgrass cultivars. Half of the plants received soil inoculum that had been autoclaved, the other half received intact, living soils. We measured above- and belowground biomass production, and examined the root tissue for evidence of AMF colonization. Generally, sorghum inoculated with sterile soils produced more biomass. For plants growing in soils from ‘Southlow’ fields, this difference was weaker in fertilized soils. Colonization of the roots by AMF was low, but hyphae were abundant in living soils. Many of these could belong to parasitic or saprophytic species of fungi. Non-beneficial organisms may outnumber mutualists in the LTER Cellulosic Biofuel plots. This could be a result of legacies left by agriculture on the microbial community or encouraged by monoculture switchgrass plantings. Future work will continue to examine these relationships, and also test the time necessary for AMF colonization in the greenhouse.