This study was conducted to evaluate the effects of vegetation, N fertilize
rs, and lime addition on landfill CH4 oxidation. Columns filled with compac
ted sandy loam and sparged with synthetic landfill gas were used to simulat
e a landfill cover. Grass-topped and bare-soil columns reduced inlet CH4 by
47 and 37%, respectively, at peak uptake; but the rate for both treatments
was about 18% at steady state. Nitrate and NH4 amendments induced a more r
apid onset of CH4 oxidation relative to KCl controls. However; at steady st
ate, NH4 inhibited CH4 oxidation in bare columns but not in grassed columns
, Nitrate addition produced no inhibitory effects. Lime addition to the soi
l consistently enhanced CH4 oxidation. In all treatments, CH4 consumption i
ncreased to a peak value, then declined to a lower steady-state value; and
all gassed columns developed a pa gradient Neither nutrient depletion nor p
rotozoan grazing could explain the decline from peak oxidation levels. Ammo
nium applied to grassed cover soil can cause transient reductions in CH4 up
take, but there is no evidence that the inhibition persists. The ability of
vegetation to mitigate NH4 inhibition indicates that results from bare-sop
tests may not always generalize to vegetated landfill caps.