title: Evidence for the importance of litter as a co-substrate for MCPA dissipation in an agricultural soil.
abstract: Environmental controls of 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation are poorly understood. We investigated whether microbial MCPA degraders are stimulated by (maize) litter and whether this process depends on concentrations of MCPA and litter. In a microcosm experiment, different amounts of litter (0, 10 and 20 g kg(-1)) were added to soils exposed to three levels of the herbicide (0, 5 and 30 mg kg(-1)). The treated soils were incubated at 20 °C for 6 weeks, and samples were taken after 1, 3 and 6 weeks of incubation. In soils with 5 mg kg(-1) MCPA, about 50 % of the MCPA was dissipated within 1 week of the incubation. Almost complete dissipation of the herbicide had occurred by the end of the incubation with no differences between the three litter amendments. At the higher concentration (30 mg kg(-1)), MCPA endured longer in the soil, with only 31 % of the initial amount being removed at the end of the experiment in the absence of litter. Litter addition greatly increased the dissipation rate with 70 and 80 % of the herbicide being dissipated in the 10 and 20 g kg(-1) litter treatments, respectively. Signs of toxic effects of MCPA on soil bacteria were observed from related phospholipid fatty acid (PLFA) analyses, while fungi showed higher tolerance to the increased MCPA levels. The abundance of bacterial tfdA genes in soil increased with the co-occurrence of litter and high MCPA concentration, indicating the importance of substrate availability in fostering MCPA-degrading bacteria and thereby improving the potential for removal of MCPA in the environment.
authors.affiliation: Institute of Soil Science and Land Evaluation, Soil Biology, University of Hohenheim, Emil-Wolff-Str. 27, D-70593, Stuttgart, Germany.|Department of Biology and Biochemistry, Birzeit University, P.O. Box 14, Birzeit, West Bank, Palestine.
authors.forename: Omar
authors.initials: O
authors.lastname: Saleh
authors.affiliation: Institute of Soil Science and Land Evaluation, Biogeophysics, University of Hohenheim, Emil-Wolff-Str. 27, D-70593, Stuttgart, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Pagel
authors.affiliation: Institute of Soil Science and Land Evaluation, Soil Biology, University of Hohenheim, Emil-Wolff-Str. 27, D-70593, Stuttgart, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Enowashu
authors.affiliation: INRA, UMR 1347 Agroécologie, 17 Rue Sully, BP 8 6510, F-21065, Dijon, Cedex, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Devers
authors.affiliation: INRA, UMR 1347 Agroécologie, 17 Rue Sully, BP 8 6510, F-21065, Dijon, Cedex, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Martin-Laurent
authors.affiliation: Institute of Soil Science and Land Evaluation, Biogeophysics, University of Hohenheim, Emil-Wolff-Str. 27, D-70593, Stuttgart, Germany.
authors.forename: Thilo
authors.initials: T
authors.lastname: Streck
authors.affiliation: Institute of Soil Science and Land Evaluation, Soil Biology, University of Hohenheim, Emil-Wolff-Str. 27, D-70593, Stuttgart, Germany.
authors.forename: Ellen
authors.initials: E
authors.lastname: Kandeler
authors.affiliation: Institute of Soil Science and Land Evaluation, Soil Biology, University of Hohenheim, Emil-Wolff-Str. 27, D-70593, Stuttgart, Germany. christian.poll@uni-hohenheim.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Poll
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000378:metabolism* / Q000633:toxicity; D000383:Agriculture; D001419:Bacteria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D004875:Ergosterol / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis; D005658:Fungi / Q000187:drug effects / Q000378:metabolism; D005798:Genes, Bacterial; D006540:Herbicides / Q000378:metabolism; D059013:Microbial Consortia / Q000187:drug effects*; D012987:Soil; D012989:Soil Pollutants / Q000378:metabolism*; D003313:Zea mays
chemical_list: D005227:Fatty Acids; D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D008456:2-Methyl-4-chlorophenoxyacetic Acid; D004875:Ergosterol
keywords: Degradation; Litter; MCPA; PLFAs; Toxicity; tfdA gene