FECAL BACTERIA SURVIVAL AND INFILTRATION THROUGH A SHALLOW AGRICULTURAL SOIL - TIMING AND TILLAGE EFFECTS

Human and livestock exposure to Fetal pathogens via contaminated surfa ce or groundwater is an important water quality concern for soils rece iving animal wastes. The effects of manure application timing (spring or fall application) and soil management (no-tillage or conservation t illage) on fecal bacteria infiltration through shallow karat soils in central Kentucky (the Bluegrass region) have not been evaluated. We pe rformed a field experiment to measure fecal coliforms and fetal strept ococci in leachate from dairy manure-amended no-tillage and conservati on tillage soils, Manure significantly increased fetal bacteria in lea chate compared with unmanured treatments. After manure application, th e leachate that collected in zero-tension lysimeters 90 cm below the s oil surface contained up to 6 x 10(4) fecal coliforms/100 mt and gener ally exceeded 3 x 10(3) fecal coliforms/100 mt. Neither the timing nor the tillage method significantly affected fecal coliform concentratio ns in leachate. Fecal bacteria in leachate declined to nondetectable l evels within 60 d of manure application. In the well structured soil u sed in this experiment, fecal bacteria moved below the crop mot zone w henever there was rainfall of sufficient duration or intensity to reus e flow after manure application, Manure application to no-tillage soil in spring did not accelerate water contamination by fetal coliforms r elative to fall manure applications. No-tillage did not accelerate wat er contamination by fecal coliforms relative to tilled soils, The pote ntial for groundwater contamination depended on soil structure and waf er pow more than on fecal bacteria survival at the soil surface.