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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #318402
Title: Rainfall intensity effects on removal of fecal indicator bacteria from solid dairy manure applied over grass-covered soil

Author
item BLAUSTEIN, RYAN - University Of Maryland
item HILL, ROBERT - University Of Maryland
item MICALLEF, SHIRELY - University Of Maryland
item Shelton, Daniel
item Pachepsky, Yakov

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2015
Publication Date: 1/4/2016
Citation: Blaustein, R., Hill, R., Micallef, S., Shelton, D.R., Pachepsky, Y.A. 2016. Rainfall intensity effects on removal of fecal indicator bacteria from solid dairy manure applied over grass-covered soil. Science of the Total Environment. 539:583-591.

Interpretive Summary: Manure contains large populations of bacteria; some of them, such as E. coli and enterococci, are used as indicators of fecal contamination. Indicators are released under rainfall or irrigation. It is not known if this release is controlled by the total amount of water, or by both the total amount of water and rainfall intensity. It is also not known if the slope of land affects the release. We conducted experiments measuring the release of indicator bacteria from solid manure applied to grass grown in wooden boxes during simulated rainfall. Rainfall intensity and slope did not have a significant effect on indicator release from manure. The removal of E. coli from manure exceeded that of enterococci, especially in the form of removal with infiltration. Results of this work will be of use in microbial risk assessment and predictions as they provide insights into bacterial release from solid manure.

Technical Abstract: The rainfall-induced removal of pathogens and microbial indicators from land-applied manure with runoff and infiltration greatly contributes to the impairment of surface and groundwater resources. It has been assumed that rainfall intensity and changes in rainfall intensity during a rainfall event do not affect microbial removal when expressed as a function of rainfall depth. The objective of this work was to test this assumption by measuring the removal of Escherichia coli, enterococci, total coliforms, and chloride ion from dairy manure applied in soil boxes containing fescue, under 3, 6, and 9 cm hr-1 of rainfall. Runoff and leachate samples were collected during each event at increasing time intervals, and after rainfall ceased, soil samples were taken at 0, 2, 5, and 10 cm depths. Rainfall intensity appeared to have positive effects on rainwater partitioning to runoff. Bacterial removal with runoff occurred in two stages, and three kinetic-based models were fitted to the data. While rainfall intensity generally did not impact removal model parameters, it had substantial inverse effects on the relative numbers of bacteria that remained in soil after rainfall. As rainfall intensity and soil profile depth increased, the numbers of indicator bacteria tended to decrease. The removal of E. coli from manure exceeded that of enterococci, especially in the form of removal with infiltration. This work may be used to advance parameterization of models that simulate bacterial removal with runoff and estimations of depths of bacterial removal with infiltration, both of which are critical to risk assessment of microbial fate and transport in the environment.