Influence of plant growth promoting Rhizobacteria on pest populations, soil mesofauna, and soil health in bermudagrass hay fields

In the southeast United States, bermudagrass (Cynodon spp.) is predominately utilized for hay production due to its pronounced response to nitrogen fertilizer applications. While nitrogen fertilizers remain a vital tool in the agricultural industry, biological alternatives may help reduce the impacts of nitrogen inputs on the environment. Recent studies suggest that certain strains of plant growth promoting rhizobacteria (PGPR) can reduce chemical fertilizer inputs while maintaining high yield and quality in hay production. In this study conducted over 2 years, two bermudagrass fields managed for hay were used to determine how PGPR and nitrogen fertilizer (ammonium sulfate) effect forage biomass, soil mesofauna and pest populations, and soil health. Plots were treated with a PGPR strain or blend with or without nitrogen, with full or half rate nitrogen or left untreated. Soil samples were taken at four harvest dates each year by extracting two cores from each plot. Samples were placed into Tullgren funnels for 48 hours to collect mesofauna samples (mites and collembolans). Soil samples were also used to determine soil respiration, which was evaluated annually using a drying and rewetting technique. No differences were identified in pest populations between treatments. However, plots treated with DH44 and a half rate of nitrogen yielded the highest forage biomass. Furthermore, DH44 treatments typically had greater populations of soil mesofauna and greater soil respiration over the 2 years.