Pathogens Pathways – Riparian Management III
1. Executive summary
Objective 9 of the Pathogen Transmission Routes Research Programme (PTRRP) focused upon two areas of related research, with the following aims:
- To quantify the generation and faecal contamination of surface runoff upon rolling dairy land.
- The development of riparian management guidelines, with respect to faecal microbes.
Faecal contamination of surface runoff generated upon dairy pasture
This research was conducted in collaboration with Massey University with the details and results presented along with those from the closely aligned drainage studies, in an integrated report (Hedley et al. 2005). Three key findings arose from the surface runoff research and are summarised in this report, these were:
- Despite the presence of subsurface drains, appreciable surface runoff can be generated upon dairy pasture. For example, 46mm and 179mm of surface runoff were generated upon one study plot during 2003 and 2004, respectively. This compared with 258mm and 388mm of subsurface drainage from the same plots over 2003 and 2004 respectively.
- The surface runoff generated is contaminated by faecal microbes, with concentrations of E. coli and Campylobacter peaking at > 105 MPN 100 mL-1 and > 103 MPN 100 mL-1, respectively, immediately following grazing. Peak Campylobacter concentrations in surface runoff, generated following the application of effluent, were also > 103 MPN 100 mL-1.
- Information derived from the Ruakura experimental studies (Collins et al. 2004) suggests that riparian buffer strips would be effective at trapping most of the faecal microbes entrained within the surface runoff generated upon the Massey plots.
Riparian guidelines
Riparian management guidelines with respect to faecal microbes have been developed and are provided within this report. These consist of a qualitative component that discusses the variation in riparian buffer strip efficiency with a range of factors including slope angle, buffer width, soil type, and rate of surface runoff. In addition, quantitative guidelines for buffer design with respect to faecal bacteria are presented. These illustrate the estimated optimal buffer width for a range of slope angles, soil drainage properties and, degrees of bacterial attachment to other (e.g., soil and faecal material) particles. Important caveats are associated with the derivation of the quantitative guidelines that require the reported efficiencies to be treated as a best-case.
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Phil Journeaux
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Private Bag 3123
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Phone: +64 7 957 8313
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