Submitted to: Transactions of the ASAE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2005
Publication Date: 6/1/2005
Citation: Roodsari, R., Shelton, D.R., Shirmohammadi, A., Pachepsky, Y.A., Sadeghi, A.M., Starr, J.L. 2005. Fecal coliform transport as affected by surface condition. Transactions of the ASAE. 48(3):1055-1061. Interpretive Summary: Animal manures can contain a variety of human gastrointestinal pathogens. Runoff from manures can potentially result in the contamination of potable or recreational waters. One strategy for minimizing pathogen runoff from manures is the use vegetative filter strips. Vegetative filter strips work primarily by facilitating infiltration of water and microorganisms into the soil profile, thereby decreasing runoff. The efficacy of vegetated filter strips at removing microorganisms from manure runoff, as compared to bare plots, was tested on plots with 20% slope and sandy loam vs. clay loam soil. Cow manure was placed at the top of plots and rainfall simulated for 1 -2 hours. The vegetative filter strips dramatically decreased runoff of manure-borne microorganisms. On clay loam soil percent bacterial runoff decreased from approximately 100% to 1% on bare vs. vegetated plots, while on sandy clay loam percent bacterial runoff decreased from 25% to undetectable on bare vs. vegetated. These results indicate that vegetative filter strips can substantially reduce runoff of manure-borne pathogens.
Technical Abstract: Land application of manures is frequently recommended to recycle soil organic matter and nutrients to enhance the soil quality and crop productivity. However, contaminated manures may pose a human health risk if they reach potable or recreational water bodies. The objective of this study was to observe and quantify the effects of Vegetated Filter Strips (VFS) on surface and subsurface transport of Fecal Coliforms (FC), surrogates for bacterial pathogens, released from a surface-applied bovine manure. A two-side lysimeter with 20% slope on both sides was instrumented to monitor the surface and vertical transport of FC. Soil on one side of the lysimeter was sandy loam, while on the other side it was clay loam. Each side of the lysimeter was divided into two sub-plots (6.7 m x 7.3 m), one with grass and the other with bare soil. Plots were instrumented to collect runoff samples along the 6.7 m slope at three equidistant transects. Samples of runoff were also collected in a gutter at the edge of each plot. All plots were equipped with multi-sensor moisture probes to monitor real-time water content through the soil profile. Bovine manure was applied at the top of the slope of each plot in one-foot strips. Rainfall was simulated at 61 mm/hr using a portable rainfall simulator. Surface flow was measured and sampled at five minute intervals at three different transects and in the gutter located at the edge of each plot. Twenty four hours after simulations, soil samples were taken at incremental depths (0-50 cm). Runoff and soil samples were analyzed for fecal coliform (FC) bacteria. Results indicated that vegetated filter strips retarded water flow, therefore reducing both surface runoff and fecal coliforms. Results also indicated that while 100% of the initial population could be lost to runoff on bare plots, only 1% of the initial population was lost on vegetative plots. FC concentrations decreased with distance along the slope from the point of application. Results also showed that bare plots offered no resistance to surface flow; FC were detected in total runoff at gutter within 10 minutes of rainfall initiation. This study concluded that even for drastic slopes such as the 20%, vegetated filter strips virtually stopped the surface transport of fecal coliforms by facilitating rapid infiltrations.