Interactions of slope and canopy of herbage of three herbage species on transport of faecal indicator bacteria by rain splash D. G. Boyer and D. P. Belesky Appalachian Farming Systems Research Centre, USDA-ARS, Beaver, WV, USA Abstract 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-simulat- ing 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, orchard- grass and perennial ryegrass were lined up on horizon- tal and sloping surfaces under a rainfall simulator. The centre pot was inoculated at the soil surface with 4 · 10 10 faecal coliform bacteria (FC) just before rainfall simulation started. The species were maintained under short, moderate and tall canopy management treat- ments. 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. Keywords: rain splash, pathogen dispersal, manure, canopy structure, canopy management, slope Introduction The movement of faecal pathogens from land to surface and ground-water are of concern because of public health implications (ASM, 1999). Non-structural, best- management practices that control the timing, volume and placement of livestock manures are used com- monly to limit opportunities for faecal pathogens to enter surface and ground-water channels and reservoirs (NRCS, 1999). Grazing areas in Appalachia, USA tend to be located on slopes, where the sequential downhill movement of faecal coliform bacteria (FC) by repeated rain splash could transport FC directly to water chan- nels or reservoirs or saturated areas. Faecal coliform bacteria are facultatively anaerobic, rod-shaped, gram- negative, non-spore-forming bacteria that ferment lactose and include the faecal-origin genera; Escherichia, Enterobacter, Klebsiella and Citrobacter. Escherichia coli is usually the predominant genus. Increased infiltration capacity, water and waste diversions, and vegetated filter strips, are used to control faecal pathogen movement in surface run-off (Lim et al., 1998; Tufford and Marshall, 2002). Faecal pathogens transported by rain splash conceivably could bypass physical barriers. Gregory et al. (1959) stated that cells of E. coli move readily in rain splash and that dispersal of microorganisms by splash is very likely. Buttleworth and McCartney (1991) found that rain had the potential to remove and disperse bacteria from leaf surfaces and disperse to nearby foliage. Dunne and Leopold (1978) noted that rain splash on slopes results in net downhill movement of soil particles, with the mathematical formulation for this type of movement being defined by Zaslavsky and Sinai (1981). Although slope was found to have a significant effect on dispersal of FC, Boyer (2008) suggested that plant canopy architecture might affect dispersal by intercepting rain- drops and modifying patterns of splash droplet dispersal. Transport of faecal pathogens by rain splash can be problematical for water quality protection as well as maintenance of the health of livestock at pasture. Correspondence to: Douglas Boyer, Appalachian Farming Systems Research Centre, USDA-ARS, 1224 Airport Rd, Beaver, WV 25813, USA. E-mail: doug.boyer@ars.usda.gov Received 14 November 2008; revised 19 August 2009 Published 2009. This article is an US Government work and is in the public domain in the USA. Grass and Forage Science, 64, 432–442 doi: 10.1111/j.1365-2494.2009.00708.x 432