Nutritive quality of Coastal bermudagrass treated with plant growth-promoting rhizobacteria
Type of DegreeMaster's Thesis
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Plant growth-promoting rhizobacteria (PGPR) are naturally occurring, non-pathogenic soil bacteria that aggressively colonize plant roots. These beneficial bacteria increase nutrient uptake, pest resistance, drought tolerance, and promote root and top growth. Biofertilization with PGPR may enable reductions in nitrogen applications in hay production. The objective of this preliminary study was to determine the nutritive quality and biomass yield of Coastal bermudagrass (Cynodon dactylon) treated with PGPR in a hay production scenario. Bermudagrass sod was harvested during winter dormancy from a field maintained by a commercial hay grower. Sod was rinsed free of native soil and transplanted into 52 pots (0.0929 m2 each) containing locally sourced field soil. Bermudagrass was treated with N and irrigated 3 times per week for 15 min during establishment (68 d). Each pot was an experimental unit. Pots were arranged into four blocks and assigned treatments using a randomized complete block design. Each block contained 13 pots including one untreated control, and each block represented a replicate. Treatments were arranged in a factorial design with PGPR (Blend 20 from Auburn University), 56 kg/ha of N (full rate), and 28 kg/ha of N (half rate) each applied at different time intervals. Initial plant heights were measured using a grazing ruler, and pots were given an initial treatment at d 0. Pots were irrigated as needed. On d 28, 56, 91 and 119, plant height was measured between 0700-0800 h, then forage was harvested to a 5.08 cm stubble height, and biomass (per 0.0929 m2) was calculated. Forage was sealed in plastic bags and immediately transported to the laboratory for processing. Pots were re-treated following the assigned treatment schedule post-harvest. Dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) concentrations were determined for each harvest. Statistical analysis was performed using JMP 12.0.1 (SAS, Inc.) with significance set at P < 0.05. Data were analyzed using the MANOVA procedure. Individual date × treatment interactions were analyzed using LSMeans Contrast procedure. The control was similar to PGPR for biomass production, DM, NDF, ADF, and ADL. Full rate of N and PGPR differed in biomass production, but PGPR was similar to half rate of N at some harvest dates. PGPR was similar to the half rate of N when evaluating DM, and was similar to full rate of N at some harvest dates. For ADF, NDF and ADL, PGPR was similar to the full rate and half rate of N at some harvest dates. This study is one of the first reports on the effect of PGPR on nutritive quality of forage-type bermudagrasses. Further research is needed to explore the efficacy of biofertilization of forage bermudagrass on a larger scale.