146 Evaluation of plant growth promoting rhizobacteria on stockpiled bermudagrass

Plant growth-promoting rhizobacteria (PGPR) are non-pathogenic, soil-inhabiting, beneficial bacteria that colonize the roots of plants. Some PGPR strains are reported to increase nutrient uptake and fix atmospheric N, which suggests that biofertilization with PGPR may provide an alternative to N fertilization for forage production. In mid-August 2017, a study was initiated to evaluate PGPR as an alternative form of N fertilization for fall-stockpiled bermudagrass. Eighteen 1-m2plots were mowed to a 2.5-cm stubble height prior to stockpiling. Two strains of PGPR (Blend 20 and DH44) were selected for evaluation based on performance in greenhouse trials. Treatments included: control, fertilizer, DH44, DH44+fertilizer, Blend 20, and Blend 20+fertilizer (n = 3).Two applications of PGPR were applied at the beginning of the stockpiling season and 30 d later. Ammonium sulfate was applied at 56 kg/ha during the first PGPR application. Plots were clipped to a height of 2.5 cm in mid-November, December, and January to determine yield and nutritive value. Data were analyzed using PROC MIXED (SAS 9.4) as a completely randomized design.Yield was greater (P ≤ 0.007) for Blend 20+fertilizer, DH44, and Blend 20 (695, 673, and 664 kg DM/ha, respectively) than the control (598 kg DM/ha). Forage DM yield differed among harvest dates, with Blend 20+Fertilizer having the highest yield in January (835 kg DM/ha). Blend 20+fertilizer, control, and fertilizer treatments had the greatest effect on CP concentration (9.1, 9.5, and 10.1%, respectively). Concentrations of NDF and ADF were greatest (P ≤ 0.01) for Blend 20, Blend 20+fertilizer, DH44, and fertilizer. Percentage IVTD decreased with the later harvests (46.1, 33.8, and 39.0% in November, December, and January, respectively); however, CP was unchanged across all harvests (P3 0.12). Overall, PGPR increased DM yield of stockpiled bermudagrass while maintaining forage nutritive value similar to commercial fertilizer.