ARS | Publication request: Interaction of fecal coliforms with soil aggregates

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2007
Publication Date: November 4, 2007
Citation: Guber, A.K., Pachepsky, Y.A., Shelton, D.R., Yu, O. 2007. Interaction of fecal coliforms with soil aggregates. ASA-CSSA-SSSA International Annual Meetings, November 4-8, 2007, New Orleans, LA. Abstract 292-22. 2007 CDROM

Technical Abstract: Land-applied manures may contain various contaminants that cause water pollution and concomitant health problems. Some of these pollutants are bacteria, and fecal coliforms (FC) have been widely used as an indicator of bacterial contamination. Experiments on bacteria attachment to soil are traditionally carried out with sieved soil or with soil primary particles. Although importance of soil structure for pollutant transport through the soil has been widely recognized, limited information exists regarding bacteria interaction with soil aggregates. The objective of this work was to test the hypothesis that FC interaction with soil aggregates is affected by aggregate size, aggregate water content, and presence of suspended colloids and dissolved organic compounds originating from manure. Aggregate fractions of 3.4-4.8 mm, 4.8-7.9 mm and 7.9-9.5 mm diameters were obtained by dry sieving Tyler loam soil. Air-dry and water-saturated aggregates were submerged in water-FC and water-manure-FC suspensions at four FC concentrations for 24 h. Amount of FC associated with soil was calculated from the difference between the amount applied and the amount remaining in the suspension. Significant differences in FC interaction with air-dry and saturated aggregates were found. The maximum FC interaction was observed for air-dry aggregates in the water-FC suspension; no measurable FC amount was associated with the saturated aggregates in the same suspension. In water-manure-FC suspensions, about 2.5 times more FC was associated with the air-dry soil aggregates than with the water-saturated aggregates. Presence of manure significantly decreased the amount of FC associated with all aggregate fractions regardless of the aggregate size. FC amount associated with the air-dry aggregates was about 300 times less in the water-manure-FC suspension than in water-FC suspension. Decrease in bacteria-soil interaction as a result of soil saturation and presence of suspended or dissolved manure components can enhance bacterial mobility and affect risk of ground water contamination.