Australia is a large producer of agricultural commodities
and ideally situated to supply the expanding food markets in
Asia, particularly those arising from the expanding middle
classes of China, India and the ASEAN region.
Despite a large land area, agricultural production can be
limited by variable rainfall but mainly by the soil
Past farming practices, including inefficient use of
fertilisers combined with land clearing and sometimes an
inherent fragile soil horizon, have resulted in large areas of
acid soils and provided the need for large scale and a growing
application of agricultural limestone.
Australian agriculture earned Australian dollar (A) $150bn
($114bn**) and made up 11% of Australia’s Gross
Domestic Product (GDP) in 2014. About two thirds of
Australian agricultural production is exported mainly to China
(20%), Korea and Japan (16%) and ASEAN (14%).
The grain-producing agricultural zone of Western Australia
is located in the south-west of Australia. In New South Wales
the grain production areas are located in the slopes and plains
regions to the west of the Great Dividing Range and on the
northern coastal floodplains to the east of the Great Dividing
Range. Victoria’s grain farms are predominantly
located in western and northern Victoria, with the majority in
the Mallee and Wimmera regions.
In South Australia grain cropping is mainly north and east
of Adelaide and on the Eyre Peninsula. The South East
region of South Australia was traditionally regarded as a
grazing area but cropping is increasing in this area.
The grain producing agricultural zone of Queensland is
located largely in the south of the state and within 400 km of
the coast. However, Queensland crop production by value is
predominantly sugarcane followed by cotton, wheat and
|Figure 1 Australian wheat planted area ('000
|Source: Department of Agriculture & Water
|Figure 2 Australian wheat production ('000
|Source: Department of Agriculture & Water
|Figure 3 Australian canola planted area ('000
|Source: Australian Oilseeds Federation
|Figure 4 Australian canola production ('000
|Source: Australian Oilseeds Federation
About 60% (12.7m hectares (Ha)) of Australian cropping area
is used for wheat production and although Australia only
accounts for about 3% of world production, the majority (70%)
is exported and Australia holds about 10-15% of the global
wheat trade. Similarly, about 70% of barley produced, which
accounts for 20% (4.1m Ha) of cropping area, is exported.
The wheat cropping area in Australia has been relatively
constant in recent years (Figure 1) although
production has varied significantly due to seasonal climate
and rainfall (Figure 2). Cropping area rather than
production is the prime indicator of fertiliser or
agricultural limestone demand.
Canola is the major oilseed crop in Australia which account
for about 11% (2.5m Ha) of total Australian cropping area.
Canola plantings commenced in 1993 and grew rapidly due to
two decades of successful breeding research (Figures 3 and
4). About 75% of production is exported making up 15-20% of
the global export trade.
Around 95% of sugar produced in Australia is grown in
Queensland and about 5% in northern New South Wales. About 75%
of sugar production is exported.
Sugarcane is a vigorous tropical grass and has very high
nutrient requirements to produce commercial crops. The majority
of cane growing soils are poor, and this combined with the high
nutrient removal rates of the crop, mean that a full suite of
nutrients must be applied every year to ensure high
Soil pH for optimum sugar cane production is between 5.5 and
7.5 and addition of agricultural limestone can be used to
correct for acidification caused by application of ammonia or
urea-based nitrogen and phosphorus fertilisers. Replacement of
calcium (Ca) and magnesium (Mg) taken up by the sugarcane is
also required and dolomite or limestone/magnesite blends are
used to provide the required magnesium.
|Figure 5 Surface soil acidity
|Source: Soil Quality
Australia’s current soil
Only 6% of the total soil in Australia is considered
In 2015, the Australian government established a set of
national science and research priorities with corresponding
practical research challenges. Soil and water was one of nine
priorities and one of the largest recipients of government
The impact of European farming practices on Australian land
and soil degradation was particularly severe from settlement up
until the 1950s. Erosion control procedures became more
prevalent after that period and farming practices and soil
management have steadily become more sophisticated and
effective. However significant problems still exist; soil
erosion is still a problem in some parts of Australia where
erosion rates are 1,000 times the rate of soil formation;
northern Australia is deficient in nutrients while the southern
region has excess; soil compaction is widespread and soil
organic stocks are low.
Finally, soil acidification in a number of cropping regions
is a major factor restricting soil use and crop yields.
|Figure 6 Western Australian agricultural
|Source: Chris Gazey (DAFWA) & Lime WA
|Figure 7 Victoria agricultural limestone
|Source: Victoria Department of State Development,
Business and Innovation
|Figure 8 New South Wales agricultural
|Source: NSW Department of Industry
Soil acidification is a problem marked by a threshold which
if passed becomes a problem where the cost of repair far
exceeds the cost of prevention. This threshold or critical
value is a soil pH of about five. About 50% of Australian
agricultural land or 50m Ha have surface pH values less than
this critical value.
Soil pH in calcium chloride (pH (CaCl2) pHCa or pHCa) is the
standard method of measuring soil acidity. This test is
considered to better reflect what the plant experiences in the
soil and be more accurate than soil pH in water expressed as pH
(w). Roughly pH (CaCl2) values are about 0.7-1.0 pH units below
pH (w) values.
The extent of the problem can also be illustrated by the
respective regional soil pH profiles (Figure 6).
About 75% of surface (0-10cm) soil sample are below pH
(CaCl2) 5.5 in Western Australia with about 70% in New South
Wales and about 30% in Victoria. In both Western Australia
and New South Wales about 30% of surface soils tested are
below pH (CaCl2) 4.8, with 45% of 10-20cm and 20-30cm samples
in Western Australia below pH (CaCl2) 4.8.
There is now growing evidence that traditional agricultural
limestone application of about one tonne per hectare every ten
years is not sufficient particularly for sub-surface soils.
It is estimated 14.25m hectares of WA’s wheat
belt soils are already acidic or at risk of becoming acidic.
This erodes potential crop yields by about 9 to 12% at a cost
of almost A$500m annually. Grain growers are being encouraged
to increase application rates from 1-1.5 tonnes /Ha to over 2
tonnes/Ha and to increase testing of acidity in sub-surface
In New South Wales it is estimated that over half of
intensively used agricultural land is affected by soil acidity
and lost production exceeds $400m annually. Canola farmers were
reported to be using 2.5 tonnes of limestone/Ha before initial
crops and 1.8 tonnes/Ha after twelve years.
Recent trials in south-west Victoria have indicated that
subsurface acidity is a bigger problem than previously thought
and that surface application of limestone can take more than
three years to increase pH below 10cm if at all.
More than 2.5m Ha are at risk of soil acidification in South
Australia with 60% of agricultural land in the Adelaide-Mt
Lofty region in South Australia susceptible to soil acidity.
Soil pH monitoring and investigation programs through from
2007 to 2012 indicated that in acid prone areas, 40% of
topsoils and 48% of subsurface layers (10–20 cm)
were below a critical level of pH(CaCl2 ) 5. Subsurface
acidity is an established problem that is more difficult to
treat. As an example, an estimate of the annual limestone
requirement for one part of the region is 28,000 tpa, an
increase of 50% from the current rate of about 18,000 tpa.
Acid Sulphate Soils
Acid Sulphate Soils (ASS) are soils or sediments containing
highly acidic soil horizons or layers resulting from the
aeration of soils or sediments that are rich in iron sulphides,
commonly pyrite. This aeration (oxidation) produces acid
(particularly hydrogen and aluminium ions) in excess of the
soils or sediments capacity to neutralise the acidity,
resulting in soils or sediments with pH (CaCl2) 4 or less.
ASS occur naturally over extensive low-lying areas of
Australia’s eastern coastal floodplains and
particularly in coastal Queensland and New South Wales. If
disturbed, ASS can release large quantities of leachate
containing acid and metal contaminants into the
Soils are divided into two categories: AASS-Actual Acid
Sulphate Soils and PASS-Potential Acid Sulphate Soils.
Queensland State Planning Policy 1/00 Planning and management
of coastal development involving acid sulphate soils is a key
document, particularly Annex 3 which specifies the tonnages
of agricultural limestone required.
Traditional limestone spreading techniques are not adequate
for ASS/PASS and soil recycling is more effective in order to
add the very high levels required (reported up to 270 Kg
agricultural limestone per tonne of ASS or PASS).
Australian limestone geology
Limestone is a very common and often impure sedimentary rock
consisting of 90% or more of calcite (CaCO3), with the 10%
being a mixture of dolomite (CaCO3.MgCO3) and various
impurities, such as silica.
Marble could also be considered 'limestone’,
even though it has been recrystallised through metamorphism. In
many applications, marble and limestone are
The most common source of calcium carbonate in the world is
limestone itself, but in some places other calcareous
sediments or other calcareous materials, such as coral, are
High quality CaCO3 is available from lime sand, limestone and
dolomite sources; with limesand being the most dominant
source. Limestone for agriculture is mined and crushed from
the state’s coastal Tamala limestone deposits.
This limestone is 1–2 million years old and was
formed by cementation of limesand deposits.
Marble formed by the metamorphism of limestone is an
important source of calcium carbonate in South Australia, as is
shellgrit, an unconsolidated accumulation of sea shell debris
found in beach ridge deposits along the coastline.
Tertiary aged limestone is mined for agricultural uses by
Sibelco Ltd at their Caroline deposit, 25km southeast of
Mount Gambier. Extensive tertiary aged deposits occur in
South Australia on the Yorke Peninsula, in the Gambier
Embayment of the Otway Basin, the Murray Basin, and in the
Limestone in Victoria varies in age from Palaeozoic to
Quaternary, with younger limestones often being friable and
porous, and older limestones being dolomitised and
silicified, or metamorphosed and recrystallised to marble.
According to the Geological Survey of Victoria (GSV), the
state’s Palaeozoic limestones and dolomites are
higher grade deposits which formed in marine settings
(typically >95% CaCO3), whereas tertiary limestones were
formed in a range of subaqueous and subaerial environments
(typically 75-95% CaCO3).
In addition, Victoria is host to Cambrian aged limestones
which are yet to be exploited.
Limestone deposits suitable for agricultural use are
widespread in the state. Limestones of tertiary age occurring
in the southern part of the state (from South Australian
border to East Gippsland) have historically been the main
source of agricultural lime.
New South Wales
New South Wales (NSW) has abundant resources of limestone.
Researchers and companies have taken particular interest in NSW
due to its high purity deposits.
There are over 400 limestone deposits known in NSW scattered
across the state. Despite this, most of them remain undeveloped
due to the local competitiveness and size of the local market.
According to work carried out by the NSW
Government’s Geological Survey, the areas with
greatest potential for high purity limestone occur south of
Yass, northeast of Cooma, near Bathurst, north of Tamworth,
around Ashford and from Molong to Canowindra.
Most limestones in those aforementioned areas are biogenic in
nature, and tend to form long, comparatively narrow bodies
with abrupt margins.
Queensland is host to a large suite of regions prospective
for economical limestone resources. The Chillagoe Formation,
Broken River Province, New England Origin, and Burdekin Basin
are all known to contain significant limestone resources.
Agricultural limestone production and
Published agricultural limestone application in grain
growing areas of Western Australia is approximately 1.6m tonnes
pa and has grown rapidly particularly due to increasing canola
production (Figure 6). Total agricultural limestone
application in Western Australia is estimated to be closer to
Recent South Australian agricultural limestone production
figures are not available. Between 1998 and 2008 average
application was 110,000 tpa. The current application rate
is estimated to be still at this level.
Current Victorian agricultural limestone application is
estimated to be 500,000 tpa, although much higher levels have
been recorded in previous years and the 10 year
(2004/05-2013/14) average application rate was about 550,000
tpa (Figure 7).
The published New South Wales agricultural limestone
application rate is currently about 300,000 tpa (Figure
8). However the actual application rate averaged 450,000
tpa in the 10 years to 2006/07 and is estimated to be currently
much higher at about 600,000 tpa.
Agricultural limestones application rates in Queensland and
Tasmania have been estimated at approximately 300,000 tpa and
110,000 tpa respectively.
Total Australian production
The total agricultural limestone application in Australia
will vary annually but is estimated to be currently about 3.4m
tonnes and, based on estimated purity levels, this is
equivalent to about 2.9m tonnes at 100% CaCO3 (Table 1 and
Major Australian producers of agricultural limestone are
listed in Table 3.
|Table 1 Estimated Australian agricultural
|Source: R Flook estimates
|Figure 9 Australian agricultural
application (2.9m tonnes @ 100% CaCO3
|Source: R Flook estimates
|Figure 10 Effect of limestone particle size
on soil pH
|Source: North Carolina State University
|Table 2 Agricultural Limestone Physical
|Source: Grains Research & Development Corporation
(Project Code SFS 00026)
Purity and sizing of the agricultural limestone are the key
factors influencing liming efficiency. Available neutralising
value and calcium level are important and some magnesium is
beneficial in the agricultural limestone. Smaller agricultural
limestone particles will react more quickly than larger
particles which may provide pH control (buffering capacity)
over a longer period of time. The biggest pH change will occur
within 3-4 months and the pH may continue to increase for 6-12
months (Figure 10).
Producers of agricultural limestone in Australia commonly
publish calcium carbonate analysis and neutralising value
(N.V.) which is the acid neutralising ability compared to 100%
However, N.V. can also vary by size fraction and the more
sophisticated producers take this into account by expressing an
Effective Neutralising Value (E.N.V.). E.N.V. takes into
account both the acid neutralising ability and the liming
physical effectiveness of the different size fractions
preferably based on actual field trials.
Trials in New South Wales have shown that the minus 75
micron fraction is most effective and this rapidly decreases to
less than half the physical effectiveness at 250
On the other hand, many producers in Western Australia use a
scale that gives equal maximum effectiveness for all particles
less than 500 microns. In South Australia and Victoria,
particles below 300 microns are given equal maximum
Some other producers in other regions of southern Australia
do not publicly acknowledge the effect of particle size at all.
A national physical effectiveness (PE) scale and mandatory
reporting of particle sizes and E.N.V. would obviously be
preferable to the current situation. The New South Wales scales
which are based on field trials with commercially available
limestone products have been recommended (Table
A further refinement in the E.N.V. calculation incorporates
an allowance for particle surface area due to limestone
morphology and enables the farmers to have an even more
practical comparison of competitive sources in the first 12
months after application.
Market - developments and outlook
Correct soil pH is important for the health of a variety of
crops, with barley, canola, faba beans and lucerne being most
sensitive to soil acidity, and wheat, peas and phalaris not
being far behind.
A recent survey in central-west New South Wales has shown
that between 2000 and 2015 soil pH has declined even further in
the majority of locations. An estimated A$1bn is lost in crop
production each year due to acid soils in Western Australia and
NSW alone, and agronomists agree that more needs to be
Lisa Miller, research and extension officer at Southern
Farming Systems Victoria suggests that while application of
limestone is on the increase, further increases are
"We’ve been concentrating a lot on the top soil
(top 10cm), however there has been acidification occurring from
10-20cm in Victoria in particular. How we get limestone down
there is a bit of a concern because we’ve been
surface supplying it, which doesn’t seem to get
down to where it’s needed," Miller told
Dr Guangdi Li, principal research scientist at the NSW
Department of Primary Industries, said that "for those areas
that soil is acidic to depth, probably deep ripping with
limestone is a good option" adding that "limestone should be
incorporated into soil for the better results. It is better put
into the ground during the crop phase in mixed farming
Both Miller and Li agree that not enough limestone is being
applied in general, but that the right amount of limestone for
deep acidification is currently unknown, with laboratory and
glasshouse experiments now underway to give better insight
within the next few years.
One solution put forward by the Western
Australia’s State Limestone Strategy was a network
of regional quarries in the South West approximately 50km apart
to supply limestone into the agricultural areas. However,
serious doubts have been raised as to whether there are enough
undeveloped deposits. The solution may be simply to increase
output from existing quarries.
Extra quarries are also needed in Victoria according to
Miller, who said that "some pits have virtually run out of
agricultural limestone", adding that she is concerned that
producers will struggle to keep up with demand.
Cameron Weeks, Regional Cropping Solutions Networks
facilitator, added that many cropping paddocks in Western
Australia’s northern wheat belt now had good
phosphorus (P) levels, so P investments could also start to be
diverted to limestone.
He estimated growers could save about $15 per hectare per
year by not applying standard P rates on paddocks that had
Miller adds that the grazing industry is "very much lagging
behind the cropping industry in terms of limestone application"
and that "we are moving towards a crunch time where a lot of
grazing farms will struggle to maintain production levels".
Omya Australia have introduced 2-6 mm
Calciprill® a fine ground (< 100 micron)
limestone which is pelletised with molasses. The pellets can be
direct drilled or air seeded or sown or spread with fertilisers
Initially marketed into high value applications such as
aerial spreading, golf courses and turf farms, the product is
being tested in pasture applications.
Some initial tests have shown that pellets drilled with
phalaris seed at an effective rate of 150Kg/Ha was equally as
effective as three tonnes per hectare of broadcast agricultural
However, the benefits may have come from the
micro-environment around the seed rather than broad acid soil
Chris Gazey, senior research officer at the Department of
Agriculture and Food Western Australia (DAFWA) has estimated
that 2.5m tpa agricultural limestone (up from the current level
of 1.6m tpa) would be needed over the next ten years to recover
acidic soils in Western Australia alone.
The increasing need for agricultural limestone as well as
the rise of limestone quarry production throughout Western
Australia and inevitably the rest of southern Australia implies
that the Australian agricultural limestone industry could
potentially grow by 50% or an additional 1.7m tpa (1.5m tonnes
at 100% CaCO3) in the near future.
The potential cost benefits are also compelling. Assuming an
average cost of spread agricultural limestone of A$55/tonne the
additional cost of about A$100m pa represents less than 10% of
the potential benefit of over A$1bn pa from improved crop
|Table 3 Australian agricultural limestone
Note: Neutralising Value (N.V.) of 100% CaCO3 is 100
Source: Company reports, Lime WA, Limestone
Association of Australia, Victorian Limestone
**Conversions made September 2016
*About the authors
Dr Richard Flook has worked for both
suppliers and consumers of minerals with global companies
including Steetley plc, Anglo American, Commercial Minerals
(now Sibelco), Normandy Mining Ltd, Omya AG and Shinagawa
Richard has been CEO, Managing Director & Director of
Asian and Australasian companies. He has specialised in new
business opportunities including strategic planning, trading,
market development and acquisitions in the industrial minerals
industry and has been involved in managing and developing
mineral operations and businesses in Asia and Australasia.
Richard is a Fellow of the Australasian Institute of Mining
& Metallurgy (FAusIMM (CP)), the Australian Institute of
Company Directors (FAICD) and the Australian Institute of
Energy (FAIE). He is a graduate of Sydney University (BSc First
Class Honours, PhD) and the University of NSW (Master of
Since 2014, Richard’s has been the Managing
Principal of Mosman Resources, a private consulting business,
specialising in the production and marketing of industrial
minerals and chemicals.
Cameron (BSc Hons I) is currently industrial
minerals’ (IM) Australian Correspondent, as well
as the Managing Principal of CPIM Consulting, Australia.
Cameron performs market analysis and research as well as the
writing and research of news and feature stories, making a
point to communicate extensively with all stakeholders.
Previously, Cameron was an Industrial Minerals geologist
(and geophysicist) for the Geological Survey of NSW (GSNSW), a
State Government body, where he took the lead on various
industrial mineral projects at the same time as performing a
Before joining the GSNSW, Cameron worked on SQUIDs at CSIRO,
Australia’s federal government agency for