Interactions of slope and canopy of herbage of three herbage species on transport of faecal indicator bacteria by rain splash

The movement of faecal pathogens from land to surfaceand ground-water are of great interest because of thepublic and livestock health implications. Knowledge ofcanopy structure and how it might be managed to helpmitigate nutrient and pathogen movement in pasture isneeded to create management practices that balancelivestock production with environmental benefits.An experiment was conducted using a rainfall-simulat-ing device to test whether canopy structure of speciescommon to pastures in Appalachia, USA could bemanaged to influence dispersion of faecal pathogens.Seven pots (30-cm diameter) of white clover, orchard-grass and perennial ryegrass were lined up on horizon-tal and sloping surfaces under a rainfall simulator. Thecentre pot was inoculated at the soil surface with4 · 10 10 faecal coliform bacteria (FC) just before rainfallsimulation started. The species were maintained undershort, moderate and tall canopy management treat-ments. White clover exhibited the greatest rates oflateral and vertical dispersion of FC into the canopy,especially in the short canopy management treatmentfollowing 30 min of rainfall (about 40 mm). Lowconcentrations of faecal coliform bacteria also dispersedinto the canopies of the grass species but the differencesin concentration of FC between the grass species werenot different. When the proportion of white clover in apasture is high, the canopy should be relatively taller toreduce the likelihood of infection associated with faecalcoliform-contaminated herbage.Keywords: rain splash, pathogen dispersal, manure,canopy structure, canopy management, slope