Significant Escherichia coli Attenuation by Vegetative Buffers on Annual Grasslands

• Published in: Journal of environmental quality Vol. 35; no. 3; pp. 795 - 805
• Main Authors: Tate, Kenneth W., Atwill, Edward R., Bartolome, James W., Nader, Glenn
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy, Crop Science Society of America, Soil Science Society 01.05.2006; Crop Science Society of America; American Society of Agronomy
• Subjects: agricultural runoff; Agronomy. Soil science and plant productions; Animals; annual grasslands; Applied sciences; Bacteria; bacterial contamination; Biological and medical sciences; Buffers; California; Cattle; cattle manure; Colony Count, Microbial; Dry season; E coli; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Escherichia coli; Escherichia coli - isolation & purification; Exact sciences and technology; Feces; Feces - microbiology; filter strips; Fundamental and applied biological sciences. Psychology; Grasslands; Infiltration capacity; isolation & purification; Microbiology; overland flow; Parasites; physiology; Poaceae; Poaceae - physiology; Pollution; pollution control; Pollution, environment geology; rain; Rainfall-runoff relationships; Runoff; Surface water; Vegetation; California; United States; North America; America; INE, USA, California; Grassland; Hill; Escherichia coli; Dry matter; Rain; Selfpurification; Placement; Collector; Land slope; Bacteria; Attenuation; Agriculture; Feces; Rainy season; Waterborne transmission; Ungulata; Enterobacteriaceae; Vegetative filter strip; Bovine; Pollutant behavior; Runoff water; Project; Soils; Vertebrata; Mammalia; Dry season; Animal; Surface water; Vegetation; Infiltration; Artiodactyla; Mediterranean climate
• ISSN: 0047-2425; 1537-2537; 1537-2537
• DOI: 10.2134/jeq2005.0141

ABSTRACT A study was conducted to estimate the retention efficiency of vegetative buffers for Escherichia coli deposited on grasslands in cattle fecal deposits and subject to natural rainfall‐runoff conditions. The study was conducted on annual grasslands in California's northern Sierra Nevada foothills, a region with a distinct wet–dry season Mediterranean climate. We used 48, 2.0‐ by 3.0‐m runoff plots to examine the efficacy of 0.1‐, 1.1‐, and 2.1‐m buffers at three land slopes (5, 20, and 35%) and four dry vegetation matter levels (225, 560, 900, and 4500 kg/ha) across 27 rainfall‐runoff events during two rainfall seasons. Buffer width treatments were implemented by placement of cattle fecal material containing known loads of E. coli 0.1, 1.1, or 2.1 m upslope of the plot runoff collector. Mean total runoff to total rainfall ratio per plot ranged from 0.014:1 to 0.019:1 and reflected the high infiltration capacity of these soils. Approximately 94.8 to 99.995% of total E. coli load applied to each plot appears to be either retained in the fecal pat and/or attenuated within 0.1 m downslope of the fecal pat, irrespective of the presence of a wider vegetated buffer. Relative to a 0.1‐m buffer, we found 0.3 to 3.1 log10 reduction in E. coli discharge per additional meter of vegetative buffer across the range of residual dry vegetation matter levels, land slope, and rainfall and runoff conditions experienced during this project. Buffer efficiency was significantly reduced as runoff increased. These results support the assertion that grassland buffers are an effective method for reducing animal agricultural inputs of waterborne E. coli into surface waters.