Sustainable Manure Management - Sustainable Animal Agriculture - page 100

of the oocysts was accelerated and samples were
infective for a shorter period (Olson et al ., 1999).
While low and high temperatures definitively
affect the survival and inactivation of oocysts,
changes in soil moisture content had little or no
effect on their inactivation (Jenkins et al ., 2002).
In contrast, Kato et al . (2002) found that inacti-
vation rates of oocysts were greater in dry soils
than in moist and wet soils that were subjected
to freeze-thaw cycles. Jenkins et al . (2002) also
reported that soil texture may influence the
inactivation of oocysts, but it could not be ruled
out if this effect was related to soil pH. However,
in a field study later conducted by Kato et al .
(2004), oocyst inactivation could not be corre-
lated with soil pH, moisture and organic matter
content.
Removal of viruses in soils occurs largely
by adsorption, with viruses surviving about
as long as pathogenic bacteria (Gerba et al .,
1975; Gilbert et al ., 1976; Sobsey et al ., 1980).
Hurst et al . (1980) found that the survival of
enterovirus, rotavirus and bacteriophage in
amended soils was influenced by temperature,
soil moisture, presence of aerobic microorgan-
isms, degree of adsorption, level of extractable
P, exchangeable aluminium and soil pH.
Overall, however, adsorption and temperature
had the greatest effect on virus survival in
soil, with virus survival decreasing with
increasing temperature. At 37°C, no enterovi-
rus infectivity was recovered from soil after
12 days, but at 4°C the virus persisted for at
least 180 days (Yeager and O'Brien, 1979).
Due to the adsorption of the virus by soils and
influence of temperature on their survival, the
land application of sewage effluent during
warm and dry months has been documented as
a viable disposal option to minimize the off-site
transport and survival of viruses (Bitton et al .,
1984; Straub et al ., 1993).

the leaching of microorganisms through soil
and other porous subsurface strata is referred to
as vertical movement. Unless a soil is saturated
or contains an impermeable barrier, vertical
movement of microorganisms will occur
(Mawdsley et al ., 1995).
Despite the existence of bacterial, viral
and protozoal pathogens in manures, few
studies to date have examined their vertical
and horizontal movement in soils under field
conditions (Thurston-Enriquez et al ., 2005;
Close et al ., 2010). As a result, knowledge of
pathogen transport in soils has largely been
inferred from studies of faecal indicator
organism movement at grazed pastures, feed-
lots and manure-amended soils (Doran and
Linn, 1979; Young et al ., 1980; Edwards et al .,
2000; Soupir et al ., 2006) or soil column
or block studies amended with pathogen-
containing livestock manure (Gagliardi and
Karns, 2000; Davies et al ., 2004; Kuczynska
et al ., 2005; Semenov et al ., 2009). Some
physical and chemical properties that influ-
ence the vertical movement of microorgan-
isms are soil type, water content and water
flow, microbe and soil particle surface proper-
ties, cell motility, pH, plant roots, tempera-
ture, and presence of micro- and meso-faunal
organisms (Mawdsley et al ., 1995; Unc and
Goss, 2004).
Rapid horizontal transport of microorgan-
isms to surface waters can occur when either
the rainfall intensity exceeds the soil's infiltra-
tion rate or when the soil becomes so saturated
that no rainfall can percolate (Tyrrel and
Quinton, 2003). Factors that influence the level
of microbiological contamination in runoff
from agricultural lands are organism die-off
rates, quantity and type of manure applied,
sloping terrain, rainfall intensity and water
infiltration rate (Evans and Owens, 1972;
Doran and Linn, 1979; Baxter-Potter and
Gilliland, 1988; Abu-Ashour and Lee, 2000;
Jenkins et al ., 2006; Ramos et al ., 2006).
Methods to mitigate the offsite transport of
microorganisms in runoff from manure-
amended soils and livestock feedlots include use
of vegetative filter strips (Coyne et al ., 1995;
Fajardo et al ., 2001) or vegetative treatment
systems with a settling basin for solids collection
and a vegetated area (Koelsch et al ., 2006; Berry
et al ., 2007). Alternatively, livestock manures

Transport of pathogens in soil

Application of livestock manures on soils, par-
ticularly surface application of manure, can
result in the transport of manure pathogens to
surface or ground waters (Abu-Ashour et al .,
1994; Jamieson et al ., 2002; Tyrrel and Quinton,
2003). The overland transport of microorgan-
isms is also called horizontal movement, while