Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract only
Publication Acceptance Date: 9/15/2005
Publication Date: 11/7/2005
Citation: Pachepsky, Y.A., Shelton, D.R., Sadeghi, A.M., Gish, T.J., Daughtry, C.S., Guber, A.K., Coppock, C.R. 2005. Spatial and temporal variability of fecal coliform at and near a manured field [abstract]. American Society of Agronomy Annual Meeting. 2005 CDROM. Interpretive Summary:
Technical Abstract: Evaluating the effect of field manure application on bacterial concentrations in creeks requires developing microbial transport models. Testing such models against bacterial monitoring data requires estimating the uncertainty in the data caused by spatial and temporal variability of bacterial concentrations. The objective of this work was to evaluate effects of sampling frequency on estimated concentrations of fecal coliforms (FC) in soil, runoff, and creek water after a spring manure application. Experiments were carried at the OPE3 ARS experimental watershed in Beltsville, MD. Manure was broadcast at a four-hectare field equipped with runoff flumes and separated from a perennial first order creek by a riparian zone. Soil was mostly sandy loam and loamy sand; it was sampled at four locations having differences in productivity mostly explained by the presence of a network of shallow groundwater pathways. Fecal coliforms in runoff and in creek water were monitored using refrigerated samplers and grab sampling. FC contents in manure varied within six orders of magnitude, and the distribution was highly asymmetrical. Before manure application, the maximum FC content in soil was found in the least hydrologically active parts of the field. A substantial increase of fecal coliforms in soil was observed during the three-week period including sites free of manure. Microponds created favorable conditions for the FC growth before the field was plowed. A two-orders-of-magnitude increase of FC in runoff was observed within a week. Significant diurnal and day-by-day dynamics of FC concentrations in the creek was observed. Because of high spatial and temporal variations, the sampling strategy to define fate and transport of manure-borne fecal coliforms can substantially affect results and may be site-specific.