New Zealand Journal of Agricultural Research abstracts
Microbial and chemical tracer movement through Granular, Ultic, and
Recent Soils
M. McLeod
J. Aislabie
J. Ryburn
A. McGill
Landcare Research
Private Bag 3127
Hamilton, New Zealand
email:mcleodm@landcareresearch.co.nz
Abstract The ability of New Zealand soils to
renovate dairy-shed effluent following application to land is being
evaluated. We investigated the pattern of transport of faecal
coliforms, a host-specific Salmonella bacteriophage and a
non-reactive chemical tracer (Br–), when applied to large,
intact lysimeter soil cores (460 mm dia. × 520–700 mm
high) of three contrasting soils. The soils were imperfectly drained
Ultic and Granular Soils and a well-drained Recent Soil. A depth of
25 mm of dairy-shed effluent containing faecal coliforms and
spiked with bacteriophage and Br– was applied to the soil at
a rate of 5 mm h–1 followed by up to 1 pore volume of
simulated rainfall applied at 5 mm h–1. This
application rate is generally much slower than the soil’s saturated
hydraulic conductivity except in the Ultic Soil where saturated
hydraulic conductivity is slower. Resulting leachates, collected
continuously, were analysed for the microbial and bromide tracers. The
phage tracer moved rapidly through all soils, peaking early in the
leachates and then tailing off in a pattern indicative of bypass flow.
Faecal coliforms also moved rapidly through the Ultic and Granular
Soils but numbers were much lower or not detectable in leachate from
the Recent Soil. In contrast, bromide moved uniformly through Granular
and Recent Soils but peaked early at about 0.5–0.8 pore volume. The
microbial data suggest the soil structure in the Ultic and Granular
Soils makes them vulnerable to leaching of microbes into shallow water
bodies.
Keywords microbial contamination; soil; bypass
flow; dairy-shed effluent
A04036; ; Received 28 April 2004; accepted 20 September 2004; Online
publication date 15 December 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47:
557–563
0028–8233/04/4704–0557 © The Royal Society of New Zealand 2004
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