title: Perennial crop growth in oil-contaminated soil in a boreal climate.
abstract: Soil contamination by petroleum hydrocarbons is a global problem. Phytoremediation by plants and their associated microorganisms is a cost-effective strategy to degrade soil contaminants. In boreal regions the cool climate limits the efficiency of phytoremediation. The planting of oil-tolerant perennial crops, especially legumes, in oil-contaminated soil holds promise for great economic benefits for bioenergy and bio-fertilizer production while accelerating the oil degradation process. We established a multi-year field experiment to study the ecological and agronomic feasibility of phytoremediation by a legume (fodder galega) and a grass (smooth brome) in a boreal climate. In 40 months, soil oil content decreased by 73%-92%, depending on the crop type. The oil degradation followed first-order kinetics with the reduction rates decreasing as follows: bare fallow > galega-brome grass mixture > brome grass > galega. Surprisingly, the presence of oil enhanced crop dry matter and nitrogen yield, particularly in the fourth year. The unfertilized galega-brome grass mixture out-yielded the N-fertilized pure grass swards over years by an average of 33%. Thus, a perennial legume-grass mixture is both ecologically and agronomically sustainable as a cropping system to alleviate soil contamination in the boreal zone, with considerable potential for bioenergy and bio-fertilizer production.
authors.affiliation: Department of Environmental Sciences, PO Box 65 (Viikinkaari 2a), 00014 University of Helsinki, Helsinki, Finland. Electronic address: lijuan.yan@helsinki.fi.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Yan
authors.affiliation: Department of Environmental Sciences, PO Box 65 (Viikinkaari 2a), 00014 University of Helsinki, Helsinki, Finland.
authors.forename: Petri
authors.initials: P
authors.lastname: Penttinen
authors.affiliation: Department of Food and Environmental Sciences, PO Box 27 (Latokartanonkaari 11), 00014 University of Helsinki, Helsinki, Finland.
authors.forename: Asko
authors.initials: A
authors.lastname: Simojoki
authors.affiliation: Department of Agricultural Sciences, PO Box 27 (Latokartanonkaari 5), 00014 University of Helsinki, Helsinki, Finland.
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Stoddard
authors.affiliation: Department of Environmental Sciences, PO Box 65 (Viikinkaari 2a), 00014 University of Helsinki, Helsinki, Finland.
authors.forename: Kristina
authors.initials: K
authors.lastname: Lindström
mesh_terms: D001673:Biodegradation, Environmental; D002980:Climate; D006838:Hydrocarbons; D010578:Petroleum / Q000032:analysis / Q000378:metabolism*; D059392:Petroleum Pollution; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D006838:Hydrocarbons; D010578:Petroleum; D012989:Soil Pollutants
keywords: Biological nitrogen fixation; Crop growth; Fodder galega; Oil degradation; Phytoremediation