AgriBusiness News September 2016

18 WAIKATO AGRIBUSINESS NEWS September 2016
Soil properties critical when applying effluent
Dairy effluent is a great source of nutrients
for growing pasture.
But if not managed properly
effluent can also be
a significant source of
contaminants which harm our
waterways.
Understanding how soil
properties affect nutrient loss
is a key to maximising the
benefits of effluent on farm
and minimising its impacts on
waterways.
Soil texture and structure
determine the amount of water
that can enter and be retained
within a particular soil, and the
rate of transmission of excess
water through that soil.
So effluent irrigation systems
should be matched with
soil properties to minimise runoff
and leaching.
The rate at which effluent
can be applied to the land for
maximum production benefit
is determined by the soil’s
properties including structure,
porosity and infiltration rate.
The nature of the effluent
and cattle treading on soils
can affect the infiltration
rate. Treading damage, which
occurs most when the soils are
wet, significantly reduces the
infiltration rate. For some soils
this can result in accumulation
of effluent below slopes and
in hollows. It can then enter
surface waterways.
Movement of water
through soil pores is generally
described as hydraulic conductivity.
When hydraulic conduc-
tivity of the soil is low, irrigation
of effluent will result in
ponding and run-off once the
total water capacity of the soil
is exceeded or if application
rate exceeds infiltration rate.
Low rates of hydraulic conductivity
are found in soils that
are poorly drained, and ponding
and runoff often occur with
high rainfall. Many of these
soils are artificially drained to
reduce the incidence of ponding
and water-logging, and this
carries a risk that effluent can
bypass the soil and be directed
rapidly into waterways
Leaching occurs as excess
water moves through the soil.
So soils with lower water
holding capacity are more
susceptible to leaching, while
soils with high water holding
capacity (deep silt loams) can
store significant quantities of
effluent.
The soils that have low
available water holding capacities,
are the shallow to moderately
deep soils, as well as
sandy or stony soils. Effluent
irrigation on these soils is likely
to result in leaching unless
it is applied at low rates and
in small doses. The irrigation
system on these soils must be
capable of low rates of application
to gain the maximum
nutrient benefit.
Drainage and the level of
biological activity of the soil at
the application site are important.
Aim to apply effluent at
a rate that keeps it in the root
zone so that the nutrients can
be utilised by pasture.
Permeable soils with a deep
water table and no drainage
limits are best for putting effluent
on. However, on stony soils
the risk of effluent draining
directly to ground water would
be an issue to consider. In such
situations, application depths
and rates should be adjusted to
account for this risk.
Another issue is “bypass
flow”. When effluent application
rates are higher than
infiltration rates, water can
enter continuous macro-pores
that are open at the soil surface,
and then move very
rapidly via so-called “bypass
flow” through a relatively dry
soil matrix. This means little
opportunity for the water to be
retained within the root zone
and high leaching of nitrate is
likely to occur.
Bypass flow of farm dairy
effluent can occur in soils that
undergo shrinkage and fissuring
during drying, especially
when these soils have been
previously compacted by
treading.
A key to avoiding over
application can be having adequate
effluent storage so that
By Bala Tikkisetty
Sustainable agriculture advisor at
Waikato Regional Council
Mark McHardy wins Cooperative
Leader of the Year Award
Cooperative Business New
Zealand has announced
Farmlands Fuel general
manager, Mark McHardy, as
the winner of the Cooperative
Leader of the Year Award for
2015/16.
The award honours an individual
who has shown significant
co-operative leadership, commitment
and support of well recognised
and accepted co-operative
principles.
They also need to display
vision and courage for the
co-operative model, along with
demonstrate successful initiatives
that have benefited their
co-operative or the co-operative
sector.
Cooperative Business New
Zealand CEO, Craig Presland,
says that Mark was the stand out
nominee for this award.
“His business’ successes as
general manager of Farmlands
Fuel have been based in strong
co-operative principles such as
leveraging the collective buying
power of the group, displaying
a strong vision and determination
in ensuring full health and
safety compliance, implementing
systems and procedures that
have ensured the efficient and
sustainable supply of fuel and
irrigation can be deferred if
conditions aren’t right.
DairyNZ has released a
new smart phone app to help
farmers apply effluent more
efficiently. The Dairy Effluent
Spreading Calculator app provides
dairy farmers and effluent
spreading contractors with
leading the long-term survival
and growth of Farmlands’ fuel
business,” he says.
Farmlands Co-operative
CEO, Peter Reidie says Mark has
been at the forefront of growth
for Farmlands Fuel for the past
10 years and has shown decisive
leadership around the expansion
and delivery of the Farmlands
Fuel business to Farmlands’
shareholder customers and the
wider rural New Zealand community,
along with offering innovative
solutions throughout the
fuel and lubricant sector.
“Mark has contributed to not
only the success of Farmlands
guidance around nutrient application
rates based on the depth
and type of effluent they apply.
• Bala Tikkisetty is a sustainable
agriculture advisor at
Waikato Regional Council.
Contacts: bala.tikkisetty@waikatoregion.govt.nz
or 0800 800
401.
Fuel but also Farmlands
Co-operative as a whole, as a key
member of the executive team
that now guides New Zealand’s
largest rural supplies co-operative,”
he says.
“Mark has excellent focus
on customer service, has implemented
a leading environmental
awareness plan and has been a
champion in the health and safety
arena, not only within Farmlands
but in the wider fuel industry.”
Mark has a strong affinity to
rural New Zealand. He comes
from a dairy farm in the North
Island and completed a Diploma
in Horticultural Management at
Lincoln University, before working
in the grain and agricultural
chemical industries.
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