Selwyn_Times: September 28, 2022

Selwyn Times Wednesday September 28 2022
18
NEWS
Latest Canterbury news at starnews.co.nz
Nitrate levels constantly monitored
• From page 17
He’s always looking for more
innovative ways to improve the
health of the land, crops and
finished product.
More lately, that includes reducing,
monitoring and managing
greenhouse gas emissions and
nitrogen leaching, and improving
soil quality.
Overseer software calculates
their nitrous oxide and carbon
dioxide emissions as well as nitrate
leaching after the numbers
are punched in.
“We are measuring what we
are doing as the soil is the biggest
part of our business
and we want to know the impact
of fertilisers. Now we are more
fine-tuning what we are putting
on. We’ve always worked at what
we consider best practice and
that’s moved on another notch
as far as doing more testing of
paddocks directly before the crop
goes in.
“We want to know exactly how
much nitrogen is in the soil and
we’re doing more monitoring
during the growing of the crop
to ensure that the amount we put
on is very closely aligned to its
needs.”
On top of the plant tissue
testing and soil analysis, they
are monitoring soils after a crop
is harvested and putting even
more scrutiny on choosing the
PRODUCTION LINE: At the peak of the season Southbridge grower Robin Oakley hires
more than 40 staff for his vegetable operation.
following crop. This could be a
green crop to soak up nutrients
that might be left in the soil.
For three years, nitrate levels
have been measured in one
of their paddocks as part the
Sustainable Vegetables System
programme. The national
research project is analysing
nitrate uptake and leaching, the
efficiency of data and looking
at the accuracy of Overseer
predictions for potato crops.
At Oakley’s, nitrate levels are
measured throughout the soil
profile to check their movement.
Gratifying for them, the results
show that their nitrate leaching is
very low.
Oakley says they probably run
on the low side for nitrogen.
“The good thing is we are
quantifying what we are doing
and we aren’t ‘guesstimating’. We
think we’ve been operating our
farming systems pretty right just
by observations about whether
more or less nitrogen needs to
go on. Farmers have been doing
that for years with season crops,
but now we’ve got more tools to
get physical measurements and
numbers.”
Growers know by experience
what grows best after another
crop to make the most of existing
nitrogen levels in soils.
Pumpkins are a good crop to
follow broccoli or nitrogen-fixing
peas as there will still be nutrients
in the ground, but the soils
will be “hungry” if they follow
grass or wheat and more fertiliser
is needed.
“The technology has validated
what we were doing was pretty
much on the button,” he said.
“So it’s not like we’ve suddenly
found we’re putting too much
of this or not enough of that
particularly with nitrogen, which
is the main one that everyone’s
concerned about.
• Turn to page 20
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