Caring for country - Northern and Yorke Natural Resources ...

4on the land
What lies beneath the soil
Soil acidity is a problem lurking in the soils of the Northern and Yorke region, stealthily reducing productivity of
agricultural land and threatening some of the region’s other natural resources. Left untreated, acid soils will worsen until
virtually nothing will grow in them.
Jamestown farmer Lyn Moore testing for soil acidity. Photo: Mary-Anne Young
Treating acid soils ‘adds up’
Concerned about ryegrass, Lyn and John
Moore began treating acid soils in 1993.
“A local agronomist suggested that ryegrass
was more competitive than wheat on acidic
soils and this started us thinking about the
need to treat our soils,” said Lyn.
The Moores began liming paddocks, when
soil pH tests started to return results of
around five. The first paddock to be limed
was a lucerne paddock from which a large
amount of hay had been cut over the years.
Now the Moores keep an eye on their
paddock yields, and when there is a
suspicion that a paddock is not performing
as well as it should, its pH is tested and then
limed if necessary.
The property is a crop and livestock mixed
farm near Jamestown with an average
annual rainfall of 450mm.
Soils are predominantly red loams or clay
loams over a clay subsoil on the flats and
mid-slopes, with grey calcareous loams in the
hills. Cereals, canola and lucerne are grown
in rotation with legume pastures.
Paddocks are limed at a rate of 2.5 t/ha and
this is expected to last over 10 years.
This year’s cost of liming amounted to over
$112/ha with lime at $15/tonne, freight $20/
tonne and spreading $25/ha.
“It does add up when you look at all the
costs with freight being the killer but then
those costs are spread over 10 years,”
says Lyn.
“And while we can’t put a specific figure
on yield improvements, they are definitely
there.”
Soil acidification, while a natural process, is
accelerated by agricultural practices. One of the
key causes is the production of grain, hay, meat
and wool.
When these are harvested or taken from the
paddock, a considerable proportion of the
more alkaline elements are removed (such as
calcium, phosphorus and potassium) leaving
more acidic compounds behind. The higher the
production, the greater the removal and hence
rate of acidification. In a ‘closed’ ecosystem,
these plant and animal products are recycled
and returned to the soil resulting in a balanced
soil pH.
Certain fertilisers used in agricultural production
tend to produce acidic compounds such as nitrate
and sulphate. If these nutrients are not taken
up and used by plants, they can result in soil
acidification. Similarly, legumes (such as clovers,
medics, lupins, beans and peas) fix nitrogen
and produce nitrate. Unused nitrate can leach
through the soil, making it more acidic.
Some soil types are more predisposed to
acidification than others, for example, those in
high rainfall areas where clay and calcium have
been leached out over geologic time.
In the Northern and Yorke region, these
soils tend to occur in the Southern Flinders
Ranges and in the hills to the west of Clare. In
other areas, such as the lucerne flats around
Marrabel, Saddleworth, Tothill, Farrell Flat and
Bundaleer, neutral soils have become acidic
over time due to high production and removal.
The major problem with soil acidity is
that it affects soil fertility and nutrient
availability. When a soil is acidic, deficiencies
in phosphorus, magnesium, calcium and
potassium are common. Conversely, aluminium
concentrations increase, becoming toxic to
plants and severely reducing plant production.
In very acidic soils, clay minerals break down
irreversibly, leading to chemical erosion,
reduced nutrient retention and lower water
holding capacity. Heavy metals bound to clay
particles can be released into soil solution
leading to contamination of water supplies.
The most practical way of dealing with soil
acidity is to lift a soil’s pH using lime. The
alkaline product neutralises soil acidity. Rates
of lime application (in tonnes per hectare) are
based on the soil’s texture and how much the
soil pH should be increased. With lime costing
around $15/tonne and additional expenses
of freight and spreading, it can cost around
$60 /ha to spread one tonne per hectare on a
property approximately 200 km from the lime
source.
Farmers in the Northern and Yorke region are
applying lime to counteract acidity. However
across the region, the estimated amount being
applied is far less than the amount considered
necessary to balance acidification rates.
Nearly 60,000 tonnes of lime per annum is
believed to be required to balance acidification
but over the last 10 years, only about 24,000
per annum has been applied. This means that
regionally the problem is worsening and some
farmers could well be experiencing losses in
production because of soil acidity.
This article was contributed by Rural
Solutions SA soils and land management
consultants Mary-Anne Young and
Natalie Watkins
Rising water value
Less rainfall and a warming climate have
made surface water a rare commodity
pretty much everywhere in South
Australia; in the driest state in the driest
continent, water is becoming the
new gold.
And like gold, the scarcer it gets, the more
looking after it needs.
That’s why the Northern and Yorke Natural
Resources Management Board has kicked off
a new plan to make sure any surface water is
treated with the respect any precious
resource deserves.
The Board’s water officer, Jennifer Munro, said
the Board was monitoring permanent surface
water – identifying pools across the region and
setting up a program looking at water level,
water quality and plants and wildlife and was
looking for landholders with permanent water
to be part of the program.
“Rivers, creeks, floodplains and lakes are
natural features of the landscape and over
generations, people have diverted or altered
the flows of these natural watercourses to meet
specific needs,” Ms Munro said.
“It may have involved simply planting or
removing vegetation, clearing out a creek bed,
creating or enlarging a dam or constructing a
water crossing.
“Now, you need to share your plans with the
Board about anything you may want to do that
affects any natural watercourse. In specified
areas throughout the Northern and Yorke
region, a Water Affecting Activities (WAA)
permit will be needed before carrying out work
on a natural water resource.”
Ms Munro said work in areas that naturally
channel water could degrade riverbeds
and riverbanks or cause sediments to head
downstream and impact on waterways.
“There is potential for long-term damage to the
health of water resources that can affect other
dependent users including people, plants and
animals,” Ms Munro said.
Ms Munro said licensing was a positive step
forward because it helped target waterrelated
restoration and remediation projects.
Landholders are invited to be involved by
providing access to their surface water features.
Priority ground, surface and watercourse areas
have been designated in the Northern and
Yorke region where WAA permits apply.
The areas are outlined in maps in Volume D
of the NRM Regional Plan, which can be
downloaded from the Board’s website
www.nynrm.sa.gov.au. Hard copies and CDs of
the maps are available from Board offices.
Ms Munro said landholders, property managers,
councils, industry bodies or organisations
planning surface water affecting activities in
priority areas should lodge permit applications
with the Board.
For more information contact Jennifer Munro
on 8636 2361 or email jennifer.munro@nynrm.
sa.gov.au
24 Northern and Yorke Natural Resources Management Board