Attenuation and persistence of fecal indicator bacteria in vegetated buffer strips in Southern Illinois, USA

Abstract

Enteric microbial pathogens originating from agricultural practices pose a serious threat to surface water quality and human health. A two-phase study was conducted in southern Illinois that examined the ability of various riparian buffer species to attenuate fecal coliform bacteria and Escherichia coli (E. coli) in overland flow, while also assessing E. coli persistence in associated buffer soils. Plots established with giant cane (Arundinaria gigantea (Walt.) Muhl.), Kentucky Bluegrass (Poa pratensis), Orchardgrass (Dactylis glomerata L.), and non-vegetated control buffers were subjected to artificial flooding with cattle (Bos taurus) manure-laden water. Mean bacteria concentrations in overland flow exiting all plots were significantly higher than concentrations found in the source slurry. To assess E. coli persistence in plots, overland flow was collected from a simulated rainfall event 4 days following slurry application, and from natural rainfall events 22, 46, 94, 97, and 111 days after the application. Overland flow exiting all plots (including non-vegetated controls) exhibited mean E. coli concentrations significantly higher than those found in the initial slurry applied. The observed concentrations may have been the result of overland flow characteristics and high levels of ambient fecal indicator bacteria (FIB) present with plots. The moist, shaded conditions created by plot vegetation may have produced prime habitat to harbor FIB. Vegetated buffer strips (VBS) may have been effective at attenuating FIB, however, performance may have been masked by the exceptionally high ambient FIB populations that were present in adjacent soils. The young age of the VBS (\1 year) may have also influenced their seemingly poor FIB attenuation. As the VBS age, increases in above and below ground vegetative material may act to increase VBS attenuation capabilities.

Evaluation of Fecal Indicators and Pathogens in a Beef Cattle Feedlot Vegetative Treatment System

“…Although the general premise was that the fecal indicator bacteria were associated exclusively with feces, there are instances where these bacteria have been isolated or enumerated from soil with no or limited fecal inputs. For example, in Illinois, a field experiment found high numbers of fecal coliforms and E. coli in control soils neighboring the treatment plots (Beck et al, 2013), and a study of ungrazed native Nebraskan prairies found mean levels of total coliforms and Enterococcus occurred naturally in soil at 1.60E+04 and 3.39E+03 cfu g -1 dry soil, respectively (Durso et al, 2016). Data from the current study reinforce these previous results and highlight the utility of taking background or control samples when measuring microbial parameters in manure-impacted soils.…”

“…However, the transport dynamics of microbes differ from that of nutrients. The results examining the efficacy of vegetation for removal of microbes are mixed, with some researchers finding the vegetative strips to be effective at reducing microbe numbers Sullivan et al, 2007;Tate et al, 2006) and others concluding that the transport of manure-impacted runoff through vegetation either does not significantly reduce the concentration of the target bacteria or may even increase the number of fecal indicator bacteria exiting the system (Beck et al, 2013;Entry et al, 2000a;Fajardo et al, 2001). The primary mechanism of removal is thought to be from the infiltrating effect and storage capacity of soils as opposed to sedimentation and tortuous flow that occurs when manures are applied across vegetation (Powers et al, 2010).…”

Giant Cane Vegetative Buffer for Improving Soil and Surface Water Quality

“…However, no differences were obtained for soil organic matter between the giant cane and orchardgrass buffer treatments. The difference in organic matter content can be attributed to the three swine manure applications before the establishment of the treatment plots in 2008 and a single application of cattle manure in the study conducted by Beck et al (2013) on the treatment plots. Soil pH in the bare ground treatment was 0.27 units higher than in the corn treatment.…”

“…rotation with conventional tillage (Beck, 2010). Vegetative buffer treatments including Kentucky bluegrass, orchardgrass, giant cane, and a nonvegetated control (bare ground) were established in 2008 and were used for a fecal indicator study in 2008 to 2009 (Beck et al, 2013). Kentucky bluegrass is slow to establish and does not survive long in wet or drought conditions but produces high-quality dense stands under favorable conditions (Gharabaghi et al, 2006).…”

“…The details of the establishment of treatment plots and management are given in Beck et al (2013). In brief, the nonvegetated bare ground treatment was an unfertilized control.…”