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 qua
lity sites; non-filtered (NF), characteristic of ambient air in Auburn, AL
and representative of that found in rural agricultural areas; or enriched w
ith ozone (O-3) to twice-ambient O-3 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) O-3 concentrations over the entire 24-week experiment (7 May
-23 October 1997) were 22, 45 and 91 eta 11(-1), respectively, for CE NF an
d 2X treatments. Mean daytime ambient O-3 concentrations peaked in mid-May
and again in late August-late September at 50-60 60 eta 11(-1), and highest
individual ambient O-3 concentrations were recorded in late June, late Jul
y, late August and mid-September at similar to 90 eta 11(-1). Dry matter (D
M) yield was greater for CF than for NF primary-growth forage, and concentr
ations of neutral detergent fiber (NDF) were higher in 2X than in NF primar
y-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 aci
d 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 tha
n in NF primary-growth forage from the initial harvest of the late-season p
lanting. No differences were observed among treatments in DM yield or conce
ntrations of cell wall constituents in primary-growth or regrowth forages f
rom the late-season planting, although concentrations of CP, NDF and ADF te
nded to be higher in 2X than in NF regrowth forage. No differences were obs
erved among treatments in concentrations of total phenolics in primary-grow
th or regrowth forages from either planting, although concentrations of tot
al phenolics tended to be higher in CF than in NF primary-growth forage fro
m the late-season planting. Particularly in the case of early-planted bahia
grass, alterations in DM yield and quality of primary-growth and vegetative
regrowth forages were of sufficient magnitude to have nutritional and poss
ibly economic implications to their utilization for ruminant animal product
ion under existing and projected global climate scenarios. (C) 2000 Elsevie
r Science B.V. All rights reserved.