Yield and quality characteristics of bahiagrass (Paspalum notatum) exposed to ground-level ozone

Early and late season-planted bahiagrass (Paspalum notatum Flugge, cultivar ‘Pensacola’) were grown in open-top chambers (OTC) to which added air had been carbon-filtered (CF), representative of that found at pristine air quality sites; non-filtered (NF), characteristic of ambient air in Auburn, AL and representative of that found in rural agricultural areas; or enriched with ozone (O3) to twice-ambient O3 concentration (2X), representative of that found in the vicinity of large metropolitan areas. Primary-growth and regrowth forages from each planting were harvested periodically throughout the experiment from each of six OTC (two OTC/air treatment). Mean daytime (09:00–21:00 h) O3 concentrations over the entire 24-week experiment (7 May–23 October 1997) were 22, 45 and 91 ηl l−1, respectively, for CF, NF and 2X treatments. Mean daytime ambient O3 concentrations peaked in mid-May and again in late August–late September at 50–60 ηl l−1, and highest individual ambient O3 concentrations were recorded in late June, late July, late August and mid-September at ∼90 ηl l−1. Dry matter (DM) yield was greater for CF than for NF primary-growth forage, and concentrations of neutral detergent fiber (NDF) were higher in 2X than in NF primary-growth and regrowth forages from the early-season planting. Concentration of acid detergent fiber (ADF) tended to be higher in 2X than in NF primary-growth forage and was higher in 2X than in NF regrowth forage, whereas acid detergent lignin (ADL) concentration was higher in 2X than in NF primary-growth forage and tended to be higher in 2X than in NF regrowth forage from the early-season planting. Crude protein (CP) concentrations were lower in CF than in NF regrowth forage from the early-season planting and in CF than in NF primary-growth forage from the initial harvest of the late-season planting. No differences were observed among treatments in DM yield or concentrations of cell wall constituents in primary-growth or regrowth forages from the late-season planting, although concentrations of CP, NDF and ADF tended to be higher in 2X than in NF regrowth forage. No differences were observed among treatments in concentrations of total phenolics in primary-growth or regrowth forages from either planting, although concentrations of total phenolics tended to be higher in CF than in NF primary-growth forage from the late-season planting. Particularly in the case of early-planted bahiagrass, alterations in DM yield and quality of primary-growth and vegetative regrowth forages were of sufficient magnitude to have nutritional and possibly economic implications to their utilization for ruminant animal production under existing and projected global climate scenarios.