An integrated phytoremediation strategy for chloroacetamide herbicides in soil
1997
Hoagland, R.E. | Zablotowicz, R.M. | Locke, M.A.
We have tested an integrated system for phytoremediation using corn (Zea mays L.), a safener specific for chloroacetamides (benoxacor), and an inoculum of a rhizosphere-competent Pseudomonas fluorescens strain UA5-40rif capable of catabolizing these herbicides. Initial growth chamber studies with a Bosket sandy loam soil (organic matter content < 1%), benoxacor (0.75 kg ha-1) and inocula of this bacterium provided protection to corn seedlings at herbicide application rates of up to 45 and 54 kg ha-1 of alachlor and metolachlor, respectively. Satisfactory root colonization, i.e. log (10) 6.2 to 7.4 cfu g-1 root by UA5-40rif, was observed at concentrations up to 12x of these herbicide rates. Following 12 days of plant growth, alachlor concentrations in soil from safened and inoculated corn seedlings were about 25% and 35% of those observed in unplanted soil at the 12x alachlor and metolachlor rate, respectively. Additional experiments studied applications of up to 36x of formulated metolachlor. At this higher metolachlor rate, normal physiological development was observed in benoxacor-safened seedlings, although there were slight reductions in root and shoot biomass. Metolachlor residues in soil treated with the 36x rate were 89%, 80%, 75%, respectively, for the unplanted soil, corn, and corn + benoxacor treatments, while only 54% remained in corn + benoxacor + UA5-40 treatment. Results indicate that use of a combination of chemical and biological safeners (competent herbicide-detoxifying rhizobacteria) is a novel and useful approach for increasing herbicide tolerance in an agronomic crop plant for enhanced phytoremediation.
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