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Abstract
Phytoremediation can be effective for remediating contaminated soils in situ and generally requires the addition of nitrogen (N) to increase plant growth. Our research objectives were to evaluate seedling emergence and survival of plant species and to determine the effects of N additions on plant growth in crude-oil–contaminated soil. From a preliminary survival study, three warm-season grasses—pearlmillet (Pennisetum glaucum [L.] R. Br.), sudangrass (Sorghum sudanense [Piper] Stapf [Piper]), and browntop millet (Brachiaria ramosa L.)—and one warm-season legume—jointvetch (Aeschynomene americana L.)—were chosen to determine the influence of the N application rate on plant growth in soil contaminated with weathered crude oil. Nitrogen was added based on total petroleum hydrocarbon-C:added N ratios (TPH-C:TN) ranging from 44:1 to 11:1. Plant species were grown for 7 wk. Root and shoot biomass were determined and root length and surface area were analyzed. Pearlmillet and sudangrass had higher shoot and root biomass when grown at a TPH-C:TN (inorganic) ratio of 11:1 and pearlmillet had higher root length and surface area when grown at 11:1 compared with the other species. By selecting appropriate plant species and determining optimum N application rates, increased plant root growth and an extended rhizosphere influence should lead to enhanced phytoremediation of crude-oil–contaminated soil.
ACKNOWLEDGMENTS
The authors would like to thank K. J. Davis and Dr. E. E. Gbur for their assistance. This research was supported in part by the Integrated Petroleum Environmental Consortium (IPEC); U.S. Army Research Office (ARO) contract/grant DACA89-97-K-005/DAAG55-98-4-0379; and the Army Environmental Quality Technology Program, work unit EC-B06 BT25 “Biodegradation Processes of Explosives/Organics Using Cold Adapted Soil Systems.”
Notes
1DAE = Days after emergence
2The coefficient of variation for each mean is given in parenthesis.
1DAE = Days after emergence.
2The percent coefficient of variation for each mean is given in parenthesis.
1TPH-C:TN is the ratio of total petroleum hydrocarbon C to added N.
2BL denotes N fertilizer added as broiler litter.
3There was a significant N rate by plant species interaction, so all means followed by the same lower case letter in the table are not significantly different (P ≤ 0.05).
1TPH-C:TN is the ratio of total petroleum hydrocarbon C to added N.
2BL denotes N fertilizer added as broiler litter.
3There was a significant N rate by plant species interaction, so all means followed by the same lower case letter in the table are not significantly different (P ≤ 0.05).
1TPH-C:TN is the ratio of total petroleum hydrocarbon C to added N.
2BL denotes N fertilizer added as broiler litter.
3There was a significant N rate by plant species interaction, so all means followed by the same lower case letter in the table are not significantly different (P ≤ 0.05).
1TPH-C:TN is the ratio of total petroleum hydrocarbon C to added N.
2BL denotes N fertilizer added as broiler litter.
3There was a significant N rate by plant species interaction, so all means followed by the same lower case letter in the table are not significantly different (P ≤ 0.05).
