Release and runoff/infiltration removal of Escherichia coli, enterococci, and total coliforms from land-applied dairy cattle manure
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Simulating the rainfall-induced release of indicator bacteria from manure is essential to microbial fate and transport modeling with regard to water quality and food safety. Experiments were conducted to determine the effects of rainfall intensity, surface slope, and scale on the release of Escherichia coli, enterococci, and total coliforms from land-applied dairy manure. Rainfall intensity did not affect bacterial release dependencies on rainfall depth, but it did have a significant effect on the post-rainfall quantities of indicator bacteria in soil. While bacterial concentrations were evenly released into runoff and infiltration, the surface slope controlled the partitioning of total released bacterial loads. The proportion of E. coli released from manure exceeded enterococci, especially with infiltration flow. Scale had strong, inverse effects on the recovery of land-applied bacteria with runoff. These results will be used to improve microbial fate and transport models, critical for risk assessment of microbial contamination in the environment.