Kl. Weier et al., POTENTIAL FOR BIOREMEDIATION OF HIGH NITRATE IRRIGATION WATER VIA DENITRIFICATION, Journal of environmental quality, 23(1), 1994, pp. 105-110
Nitrogen fertilizer application to irrigated corn (Zea mays L.) can re
sult in N leaching from the crop rooting zone into groundwater. Microb
ial denitrification, with ethanol as an energy source, was evaluated f
or prevention of groundwater contamination under irrigated corn in Neb
raska where irrigation water NO3--N levels can exceed 30 mg L(-1). A f
ield study was conducted on a Herd silt loam (Pachic Haplustoll) in ce
ntral Nebraska by installing plastic (PVC) cylinders (28.7 cm diam. by
1.8 m long) in soil to a depth of 1.2 m and irrigating with 17.1 cm o
f water containing 30 mg L(-1) isotopically enriched (76.6 atom% N-15)
KNO3-N equivalent to 51.8 kg N ha(-1). Soil remediation treatment inc
luded addition of 10 mt ethanol (644 kg C ha(-1)) to three of six cyli
nders. Gas samples taken every 6 h for 4 d from the soil surface and s
oil profile indicated that ethanol addition stimulated microbial respi
ration and denitrification. Cumulative loss of gaseous N from the soil
surface over this period was 12.7 kg N ha(-1) or 24.5% of the added N
-15-NO3; an additional 27 kg N ha(-1) NO3 was lost from the ethanol-am
ended soil profile. In the laboratory, intact soil cores taken at five
intervals to a 132-cm soil depth adjacent to field cylinders were bro
ught to 90% WFPS (water-filled pore space) by applying treatments of e
thanol (19.8 kg C ha(-1)) and NO3- (0.88 kg NO3--N ha(-1)) and incubat
ed at 25 degrees C, with 100 mt L(-1) C2H2, for 7 d during which time
headspace gas samples were analyzed for N2O and CO2. Soil respiration
and denitrification increased with ethanol addition except in surface
soil where C availability was not limiting. We conclude that ethanol a
ddition to high NO3- irrigation water may remediate groundwater NO3- c
ontamination.