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

Authors: Boyer, Douglas; Belesky, David

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2009
Publication Date: 11/11/2009
Citation: Boyer, D.G., Belesky, D.P. 2009. Interactions of slope and canopy of herbage of three herbage species on transport of faecal indicator bacteria by rain splash. Grass and Forage Science. 64:432-442.

Interpretive Summary: Knowledge about the movement of pathogenic bacteria from manure to water supplies is important for designing and implementing practices that protect water quality. The transport of fecal bacteria by rainsplash was studied in three different forage plant species grown on slopes ranging from horizontal to 45 degrees. The three forages studied because of differing canopy architectures were white clover, orchard grass, and perennial rye grass. More bacteria were transported by rainsplash in the white clover than either of the grasses. Managing white clover with a short canopy height resulted in the most rainsplash transport of fecal bacteria compared to moderate or tall canopy management. Fecal bacteria were also found to splash further and in greater concentrations in the down slope direction, especially at the steeper slopes. The results of this study add to our knowledge about farm level transmission of fecal microorganisms and contribute to our ability to design and implement management practices that protect human and livestock health as well as the environment.

Technical Abstract: The movement of fecal pathogens from land to surface and ground water are of great interest because of the public health implications. Sequential downhill movement of fecal coliform bacteria by repeated rain splash could transport fecal coliforms directly to water bodies or areas of saturation excess where they will become entrained in overland runoff. Seven pots (30 cm diameter) of white clover, orchard grass, and perennial rye grass were lined up on horizontal and sloping (5, 10, 15, 20, 25, 35, and 45 degrees) surfaces under a rainfall simulator. The center pot was inoculated at the soil surface with 4 x 1010 FC bacteria just before rainfall simulation started. The forages were maintained under short, moderate, and tall managements. Fecal coliform concentrations in the forage canopies were determined following 30 minutes of rainfall (about 40 mm). White clover exhibited the highest rates of lateral and vertical dispersion of FC into the canopy, especially in the short canopy management. Fecal coliforms dispersed into the grass canopies too, but the concentration differences between the grasses were not statistically different. In order to reduce the opportunity of infection from contaminated forage, the use of broad-leaved forages should be managed taller and young or stressed animals should be kept off of the forage during rainy periods. The results of this study add to our knowledge about farm level transmission of fecal microorganisms and contribute to our ability to design and implement management practices that protect human and livestock health as well as the environment.