Soil fungal community responses to oilseed meal addition

Demand for bio-based fuels has sparked renewed interest in the use of oil-rich seeds for biodiesel production. Oilseed meals are a byproduct of this process. Although some can be used as animal feed, others are too toxic. Given that oilseed meals are relatively nutrient rich, land application as organic fertilizer or biofumigants represents a potential alternative use. In this study, soil bacterial and fungal community responses to amendments of a glucosinolate-containing brassicaceous oilseed meal (Brassica juncea), a non-glucosinolate-containing, non-brassicaceous oilseed meal (Linum usitatissimum), and a non-oilseed biomass (Sorghum bicolor) were characterized using replicated fungal ITS gene sequence libraries at 4 time points over the course of a 28-day laboratory incubation. We hypothesized that both oil residue and glucosinolate content would alter community composition but that effects would diminish over time. Distinct separation of the fungal communities occurred along amendment-type lines. Both flax and sorghum led to increases in OTUs resembling known plant pathogens, and dramatic decreases in fungal phylotype richness occurred following mustard seed meal addition, and these changes persisted throughout the 28-day incubation. Oilseed amendment has the potential to alter soil microbial community structure, particularly in the case of mustard.