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 surface and ground-water are of great interest because of the public and livestock health implications. Knowledge of canopy structure and how it might be managed to help mitigate nutrient and pathogen movement in pasture is needed to create management practices that balance livestock production with environmental benefits. An experiment was conducted using a rainfall-simulating device to test whether canopy structure of species common to pastures in Appalachia, USA could be managed to influence dispersion of faecal pathogens. Seven pots (30-cm diameter) of white clover, orchardgrass and perennial ryegrass were lined up on horizontal and sloping surfaces under a rainfall simulator. The centre pot was inoculated at the soil surface with 4 · 10 faecal coliform bacteria (FC) just before rainfall simulation started. The species were maintained under short, moderate and tall canopy management treatments. White clover exhibited the greatest rates of lateral and vertical dispersion of FC into the canopy, especially in the short canopy management treatment following 30 min of rainfall (about 40 mm). Low concentrations of faecal coliform bacteria also dispersed into the canopies of the grass species but the differences in concentration of FC between the grass species were not different. When the proportion of white clover in a pasture is high, the canopy should be relatively taller to reduce the likelihood of infection associated with faecal coliform-contaminated herbage.