❓ A WA parliamentary question scrutinises the Department of Primary Industries and Regional Development's online lime comparison calculator, questioning the scientific validity of its particle size assumptions and seeking supporting evidence.
AnsweredQoN 549Legislative Council
QuestionView source ↗
DEPARTMENT OF PRIMARY
INDUSTRIES AND REGIONAL DEVELOPMENT —ONLINE LIME COMPARISON CALCULATOR
549. Hon Dr STEVE THOMAS to the Minister for Regional
Development:
I refer to the Department of
Primary Industries and Regional Development's online lime comparison calculator
and longhand lime comparison.
(1) Why do both
calculations assume the same particle size discount factor of one for all
particles from zero millimetres to 0.5 millimetres?
(2) Is it
scientifically valid to assume that particles from zero millimetres to 0.125
millimetres, 0.125 millimetres to 0.25 millimetres, and 0.25 millimetres to 0.5
millimetres will all have the same neutralising value?
(3) What supporting scientific
evidence has the department used to make this assumption?
(4) Will the minister please table
that evidence?
(5) Given that
the New South Wales Fertilisers Act 1985 requires all lime to be labelled with
neutralising values for three particle sizes—zero millimetres to 0.075
millimetres, 0.075 millimetres to 0.25 millimetres, and 0.25 millimetres to one
millimetre—and the New South Wales Department of Primary Industries
attaches a different efficiency of neutralising value for each, why does the Western
Australian Department of Primary Industries and Regional Development not
distinguish between these different sized particles?
INDUSTRIES AND REGIONAL DEVELOPMENT —ONLINE LIME COMPARISON CALCULATOR
549. Hon Dr STEVE THOMAS to the Minister for Regional
Development:
I refer to the Department of
Primary Industries and Regional Development's online lime comparison calculator
and longhand lime comparison.
(1) Why do both
calculations assume the same particle size discount factor of one for all
particles from zero millimetres to 0.5 millimetres?
(2) Is it
scientifically valid to assume that particles from zero millimetres to 0.125
millimetres, 0.125 millimetres to 0.25 millimetres, and 0.25 millimetres to 0.5
millimetres will all have the same neutralising value?
(3) What supporting scientific
evidence has the department used to make this assumption?
(4) Will the minister please table
that evidence?
(5) Given that
the New South Wales Fertilisers Act 1985 requires all lime to be labelled with
neutralising values for three particle sizes—zero millimetres to 0.075
millimetres, 0.075 millimetres to 0.25 millimetres, and 0.25 millimetres to one
millimetre—and the New South Wales Department of Primary Industries
attaches a different efficiency of neutralising value for each, why does the Western
Australian Department of Primary Industries and Regional Development not
distinguish between these different sized particles?
AnswerView source ↗
I
appreciate that the member contacted us on Friday to give us notice of this
question, but I think this is the sort of question that should be put on
notice. Madam President, I seek your guidance. The answer to this very complex
array of questions is around 900 words, plus there is a tabled document.
Perhaps to save the time of the house—I have no problem giving the
material—I seek leave to table the document and incorporate the answer
into Hansard .
Leave granted.
The following material was
incorporated —
The
Department of Primary Industries and Regional Development (DPIRD) does not have
an on-line lime comparison calculator. However, various DPIRD publications
refer to an on-line lime comparison calculator that is available on the Soil
Quality Website. This website is managed by The University of Western Australia.
The
DPIRD publications seek to explain and clarify lime quality factors which
should be considered when growers are seeking to purchase agricultural lime to
manage soil acidity. These factors are neutralising value (or capacity to
neutralise acid compared to pure calcium carbonate) and particle size (a factor
which is related to the speed of the reaction between the particle and acid in
the soil) and then purchase cost and transport distances.
In the
soil quality calculator, lime particles less than 0.5 mm are all given a discount
factor of 1. This means they are all considered to be equally as effective over
a period of 1–2 years 'when applied to an acidic soil'.
No.
Agricultural limes are natural products and factors like neutralising value are
variable. In some lime sources, the finest particle size fraction has the
highest neutralising value, whereas in other sources, the largest particle size
fraction has the highest neutralising value.
It is
also reasonable to assume that the finer the particle, the quicker it is likely
to react in the soil. However, there comes a point where it is no longer cost
effective or practical to produce the very fine particles. The UWA soil quality
calculator captures this by assigning a discount factor of 1 (no discount) to
particles less than 0.5 mm.
The
calculator was not developed by DPIRD. The reference quoted on the Soil Quality
Website referring to the relative efficiencies of particle sizes is Cregan, PD,
Hirth, JR, and Conyers, MK (1989) Amelioration of Soil Acidity by Liming and
Other Amendments. In ''Soil Acidity and Plant Growth'' (AD,
Robson, ed), pp 205–264. Academic Press.
Additional
information supporting the assumptions used by the calculator are:
A
two-year particle size incubation study carried out by the Chemistry Centre of
WA on behalf of Lime WA. (AGWEST report Comparing Lime Sources -shows three
finest fractions are similar after 16 weeks)
Results
from soil acidity trials where more than one source of lime was compared. Most
recently a lower neutralising value morrel on-farm lime source has been compared with a commercial product. Rates were
adjusted using the calculator to account for quality parameters (morrel on-farm
lime 11 t/ha and commercial limes and 4 t/ha). Results of soil pH analysis
indicate that the current calculator does a reasonable job of comparing
agricultural lime sources using an estimated effective neutralising value
(ENV).
(4) [See
tabled paper no 2734.]
(5) The origin of the majority of lime used in NSW
agriculture is hard rock which is mined and ground resulting in a large
proportion of very fine material. Presumably the three sieve sizes used there
are a good descriptor for NSW lime sources.
WA lime
sources traditionally are not hard rock and are not ground. If required, they
are crushed and screened generally resulting in a much cheaper product per
tonne at the pit. The Biosecurity and Agriculture Management Act 2007,
Biosecurity and Agriculture Management (Agriculture Standards) Regulations 2013
Schedule 6 – Requirements for lime fertilisers states that: For
Agricultural Lime (First grade) 80 per cent fine material capable of passing
through a test sieve with an aperture size not exceeding 0.6 mm and must have a
Neutralizing Value of 75 per cent, further more for Agricultural Lime (Second
Grade) 60 per cent fine material and 50 per cent Neutralising Value.
These
standards provide insufficient information for growers to make informed
decisions about the actual cost of neutralising value bought and delivered on
farm.
I am
advised by DPIRD that the WA lime industry recognised this situation 20 years
ago and formed a voluntary self-regulated industry group and has been providing
to growers and consultants via the Lime WA website product information sheets
which describe their lime in terms of five sieve fractions (0–0.125,
0.125–0.250, 0.250–0.5, 0.5–1.0 and greater than 1.0
mm) with a neutralising value for each, a weighted neutralising value, a bulk
neutralising value and a three year range for each of these parameters.
appreciate that the member contacted us on Friday to give us notice of this
question, but I think this is the sort of question that should be put on
notice. Madam President, I seek your guidance. The answer to this very complex
array of questions is around 900 words, plus there is a tabled document.
Perhaps to save the time of the house—I have no problem giving the
material—I seek leave to table the document and incorporate the answer
into Hansard .
Leave granted.
The following material was
incorporated —
The
Department of Primary Industries and Regional Development (DPIRD) does not have
an on-line lime comparison calculator. However, various DPIRD publications
refer to an on-line lime comparison calculator that is available on the Soil
Quality Website. This website is managed by The University of Western Australia.
The
DPIRD publications seek to explain and clarify lime quality factors which
should be considered when growers are seeking to purchase agricultural lime to
manage soil acidity. These factors are neutralising value (or capacity to
neutralise acid compared to pure calcium carbonate) and particle size (a factor
which is related to the speed of the reaction between the particle and acid in
the soil) and then purchase cost and transport distances.
In the
soil quality calculator, lime particles less than 0.5 mm are all given a discount
factor of 1. This means they are all considered to be equally as effective over
a period of 1–2 years 'when applied to an acidic soil'.
No.
Agricultural limes are natural products and factors like neutralising value are
variable. In some lime sources, the finest particle size fraction has the
highest neutralising value, whereas in other sources, the largest particle size
fraction has the highest neutralising value.
It is
also reasonable to assume that the finer the particle, the quicker it is likely
to react in the soil. However, there comes a point where it is no longer cost
effective or practical to produce the very fine particles. The UWA soil quality
calculator captures this by assigning a discount factor of 1 (no discount) to
particles less than 0.5 mm.
The
calculator was not developed by DPIRD. The reference quoted on the Soil Quality
Website referring to the relative efficiencies of particle sizes is Cregan, PD,
Hirth, JR, and Conyers, MK (1989) Amelioration of Soil Acidity by Liming and
Other Amendments. In ''Soil Acidity and Plant Growth'' (AD,
Robson, ed), pp 205–264. Academic Press.
Additional
information supporting the assumptions used by the calculator are:
A
two-year particle size incubation study carried out by the Chemistry Centre of
WA on behalf of Lime WA. (AGWEST report Comparing Lime Sources -shows three
finest fractions are similar after 16 weeks)
Results
from soil acidity trials where more than one source of lime was compared. Most
recently a lower neutralising value morrel on-farm lime source has been compared with a commercial product. Rates were
adjusted using the calculator to account for quality parameters (morrel on-farm
lime 11 t/ha and commercial limes and 4 t/ha). Results of soil pH analysis
indicate that the current calculator does a reasonable job of comparing
agricultural lime sources using an estimated effective neutralising value
(ENV).
(4) [See
tabled paper no 2734.]
(5) The origin of the majority of lime used in NSW
agriculture is hard rock which is mined and ground resulting in a large
proportion of very fine material. Presumably the three sieve sizes used there
are a good descriptor for NSW lime sources.
WA lime
sources traditionally are not hard rock and are not ground. If required, they
are crushed and screened generally resulting in a much cheaper product per
tonne at the pit. The Biosecurity and Agriculture Management Act 2007,
Biosecurity and Agriculture Management (Agriculture Standards) Regulations 2013
Schedule 6 – Requirements for lime fertilisers states that: For
Agricultural Lime (First grade) 80 per cent fine material capable of passing
through a test sieve with an aperture size not exceeding 0.6 mm and must have a
Neutralizing Value of 75 per cent, further more for Agricultural Lime (Second
Grade) 60 per cent fine material and 50 per cent Neutralising Value.
These
standards provide insufficient information for growers to make informed
decisions about the actual cost of neutralising value bought and delivered on
farm.
I am
advised by DPIRD that the WA lime industry recognised this situation 20 years
ago and formed a voluntary self-regulated industry group and has been providing
to growers and consultants via the Lime WA website product information sheets
which describe their lime in terms of five sieve fractions (0–0.125,
0.125–0.250, 0.250–0.5, 0.5–1.0 and greater than 1.0
mm) with a neutralising value for each, a weighted neutralising value, a bulk
neutralising value and a three year range for each of these parameters.
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