167 Use of plant growth-promoting rhizobacteria in bermudagrass systems of the Southeast US

Since the discovery of plant growth-promoting rhizobacteria (PGPR) in the mid-20th century, efforts have focused on utilizing them to reduce synthetic fertilizer usage and to improve the sustainability of agricultural systems. However, research in forage systems is lacking. The objective of the current study was to determine the use of PGPR in bermudagrass (Cynodon dactylon) forage systems in Central Alabama. The study was designed as a split plot and conducted at the E.V. Smith Research and Extension Center (Shorter, AL) and compared four levels of PGPR and five levels of nitrogen fertility rates. The PGPR included a negative control, Paenibacillus riograndensis DH44, Bacillus subtilis DH267, and UrtrishaN (Corteva Agriscience, Indianapolis, IN) were allocated to main plots. The strains of DH44 and DH267 were sprayed during each application at a population of 1-5 × 108 cfu/mL while UtrishaN (Corteva) was sprayed at a population of 3×107 cfu/mL with an activator at the rate of 0.25% vol/vol according to the manufacturer’s recommendations. The nitrogen fertilizer treatments were the subplot and were 25 and 50% of the recommended nitrogen for bermudagrass. The N treatments were as follows: negative control, 25% urea, 25% ammonium sulfate, 50% urea (F4), and 50% ammonium sulfate. Plots were treated with PGPR and N fertilizer starting on 11 May 2023. The forage harvest operation was conducted with at least 4 wk intervals depending on precipitation. After one year of the study, PGPR did not have any significant effect on forage biomass (1,209 kg /ha; P = 0.58). There was also no effect of N fertilizer (1,596 kg/ha; P = 0.35) or PGPR × N fertilizer interaction on forage biomass (1,408 kg/ha; P = 0.56). The lack of differences between positive and negative control plots indicates that growing conditions (i.e., lack of timely rainfall) during the first year of the study limited forage production for all treatments. The results from future years of this study will provide a more accurate conclusion on the use of PGPR with and without N fertilizer for bermudagrass systems.