Stimulated Rhizodegradation of Atrazine by Selected Plant Species

The efficacy of vegetative buff er strips (VBS) in removing herbicides deposited from surface runoff is related to the ability of plant species to promote rapid herbicide degradation. A growth chamber study was conducted to compare (14)C-atrazine (ATR) degradation profiles in soil rhizospheres from different forage grasses and correlate ATR degradation rates and profiles with microbial activity using three soil enzymes. The plant treatments included: (i) orchardgrass (Dactylis glomerata L.), (ii) smooth bromegrass (Bromus inermis Leyss.), (iii) tall fescue (Festuca arundinacea Schreb.), (iv) Illinois bundle flower (Desmanthus illinoensis), (v) perennial ryegrass (Lolium perenne L.), (vi) switchgrass (Panicum virgatum L.), and (vii) eastern gamagrass (Tripsacum dactyloides). Soil without plants was used as the control. The results suggested that all plant species significantly enhanced ATR degradation by 84 to 260% compared with the control, but eastern gamagrass showed the highest capability for promoting biodegradation of ATR in the rhizosphere. More than 90% of ATR was degraded in the eastern gamagrass rhizosphere compared with 24% in the control. Dealkylation of atrazine strongly correlated with increased enzymatic activities of beta-glucosidase (GLU) (r = 0.96), dehydrogenase (DHG) (r = 0.842), and fluorescein diacetate (FDA) hydrolysis (r = 0.702). The incorporation of forage species, particularly eastern gamagrass, into VBS designs will significantly promote the degradation of ATR transported into the VBS by surface runoff. Microbial parameters widely used for assessment of soil quality, e.g., DHG and GLU activities, are promising tools for evaluating the overall degradation potential of various vegetative buff er designs for ATR remediation.