The presence of pathogens such as E. coli in surface and ground water bodies is an important public and private water quality issue. Livestock agriculture has been targeted as a primary source of this contamination. In agricultural soils, the disturbance of natural, macropore networks by tillage practices has the potential to alter the capacity of the soil to strain out fecal coliforms and affect their appearance in tile water discharge. We monitored the appearance of E. coli in tile drainage waters in response to the application of liquid dairy manure (LDM) on zero, minimum and conventional till plots in a corn-soybean-wheat rotation. Increased concentrations of E. coli, in excess of 650 cfu's 100 mL-1, were recorded when an application of LDM preceded a 35 mm storm rainfall event and high tile flow rates. A second spring application of LDM 24 months later did not result in an increase in counts when tile flow rates subsequent to the application remained low. During certain tile flow periods, zero till treatments resulted in higher E. coli counts, but this was not a consistent observation over time. Higher discharge rates were also conducive to the appearance of this pathogen in tile waters. Counts remained below the recreational water standard outside of peak tile flow periods, supporting the hypothesis that the appearance of fecal coliforms in tile discharge from agricultural land is event-driven.
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