Soil Acidity (pH)

Fungicide Coating Calculator

Fungicide rate (ml/ha)

Fertilizer rate (kg/ha)

Litres of fungicide required per tonne of fertilizer (l/t)

Liquid Fertilizer Quantity Calculator

Liquid Fertilizer

Application rate (l/ha)

Hectares (ha)

Tonnes of liquid fertilizer (t)

Nitrogen to Product Calculator

The amount of fertilizer required to provide a target nitrogen rate (kg/ha)

Target nitrogen rate (kg/ha)

Urea (kg/ha)

UAN (l/ha)

MAXamFLO (l/ha)

MAXamFLO sulphur applied (kg/ha)

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

Product to Nitrogen Calculator

Nitrogen applied (kg/ha) at a given rate of Liquid fertilizer (l/ha)

Liquid Fertilizer

Liquid fertilizer rate (l/ha)

Nitrogen applied (kg/ha)

Sulphur applied (kg/ha)

Urea rate equivalent (kg/ha)

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

Liquid Fertilizer Unit Convertor

Product

Amount

Units

Litres:

Tonnes:

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

Soil acidity is a major constraint to farming in the Western Australia wheatbelt. An estimated two thirds of the area are affected by soil acidification, which is accelerated by the removal of produce, leaching of nitrogen from the root zone and using ammonium-based fertilizers.

With agriculture aiming to maximise produce removal, it is acidifying by nature and therefore requires strategic planning to limit the cost to production.

Measuring Soil pH

Acidity increases with the increasing presence of hydrogen ions (H+). It is measured using the pH scale, which is a logarithm of hydrogen ion concentration in moles/L. The scale ranges from 1 to 14 with a value of 7 being neutral, values above 7 being alkaline and values below 7 being acidic. A one-unit pH change indicates a ten-fold increase in the number of hydrogen ions (e.g. pH 5.0 has 10 times the amount of hydrogen ion than pH 6.0 and 100 times the amount of pH 7.0).

Effect on crop

The availability of nutrients is affected by the pH of a soil. With increasing acidity, the macronutrients will become less available and the micronutrients will become more available.

Acidity does not affect crop growth as such, but it does increase the presence of soluble aluminium in the soil. As a result, the root growth is hindered. Aluminium will start to dissolve at a pH of 5.5 (calcium chloride) and become toxic for many species at around pH 4.5 (calcium chloride). The degree to which the plant is affected depends on its tolerance to acidity (or aluminium) and can be seen in this critical pH range graph.

Many Western Australian soils have a more acidic sub-soil and therefore greater concentration of soluble aluminium at depth. The reduction of root growth due to aluminium toxicity reduces the ability of the roots to source water and nutrients, leading to premature haying-off or droughting of the crop.

Balancing acidic soil

To balance the pH levels, first the extent of the problem must be identified. The best way to do this is to:

a) Soil test the topsoil (0-10cm), and

b) test the pH of the subsoil (10-30cm).

Subsoil acidity will take longer to rectify, as the ameliorant has to travel through a greater profile. Research presented at the 2003 Agribusiness Crop Updates by Chris Gazey (AgWA) would suggest that the topsoil has to be greater than pH 5.5 (CaCl2) for lime sand to act on subsoil acidity. Once the state of soil acidity is defined, then priorities for ameliorant application can be set to bring paddocks back to a desired pH level.

Application of ameliorant

There are a few different forms of ameliorant available in Western Australia, including lime and dolomite.

The best form to use would depend on the quality, freight rates and overall cost of the product. The quality is measured by a function of the neutralising value, particle size and hardness of the product. It is expressed as the ‘effective neutralising value’ and is used by all registered lime suppliers.

Lime sand is the most commonly used ameliorant and has also been the most researched in WA. Lime sand should be applied at a maximum of 1 to 1.5 tonne per hectare to avoid causing imbalances in the soil with other nutrients such as copper, zinc, manganese and potassium.

Calculate lime use equivalent

Once paddocks have been restored to the desired pH range (5.5 to 6.5 CaCl2), then a lime use equivalent can be calculated. This is calculated on the rotation, soil type and fertilizer regime employed to give an estimate on the lime required to neutralise the nett acidity increase. One can then incorporate an ongoing liming program into the rotation to maintain desired pH levels.

Crop selection

The selection of acid tolerant plants and species can also help minimise the cost of soil acidity. Their use should be used in conjunction with an amelioration program, as the soil is likely to continue to acidify.

Pasture
Soil Test Level
(K - ppm or mg/kg)
Cereals
Lupins
Canola*
Pulses
Low Rainfall
Medium Rainfall
High Rainfall
>120
0
0
0
0
0#
80 - 120
P.T.
0
0
10-20
20-30
60 - 80
15-20
0
10-20
20-30
30-40
40 - 60
20-25
P.T.
20-30
30-50
40-60
25-35
20-25
30-50
40-60
50-60
Product
Autumn Application
Winter Application
After 4 weeks
After 7 weeks
After 4 weeks
After 7 weeks
Amsul
3.7
6.9
1.0
2.5
Urea
59.9
58.4
36.8
38.9
Cations
Anions
Chemical Symbol & Charge
Name
Chemical Symbol & Charge
Name
K+
Potassium
NO3-
Nitrate
NH4+
Ammonium
Cl-
Chlorine
Na+
Sodium
SO4--
Sulphate
Cu++
Copper
HPO4- -
Phosphate
Zn++
Zinc
BO3----
Boron
Mn++
Manganese
MoO4- -
Molybdenum
Ca++
Calcium
Mg++
Magnesium
Fe++
Iron
N
P
K
S
Cu
Zn
Mn
Ca
Mg
Clover Pasture
25-30
3.5
16-20
2-3
0.005
0.02
0.40
0.4
1.2
Product
% N
Urea
46.0
MAXam/Amsul
21.0
UreaPlus
37.1
NitroPlus
33.4

Compounds

Product
%Ammonium-N
DAPSZC
16.4
MAPSZC
10.6
AllStar
13.0
Vigour
5.0
Product
N
P
K
S
Ca
Mg
Cu
Zn
Mn
kg per tonne
grams per tonne
Wheat
23
3
4
1.4
0.33
0.93
5
29
40
Barley
20
2.9
4.4
1.1
0.3
1.08
3
15
11
Oats
16
3
4
1.5
0.5
1.0
3
17
40
Canola
40
6.5
9.2
9.8
4.1
4.0
4
40
40
Lupins
51
3.8
8.8
3.1
1.7
1.7
5
30
60
Chickpeas
34
3.8
8.9
1.8
1.1
1.2
7
38
34
Faba Beans
39
3.8
9.8
1.4
1.1
1.0
10
28
30
Field Peas
37
4.0
8.2
2.0
0.7
1.2
5
35
14
Hay
20
2.0
25
2.0
0.5
1.1
5
20
40
Milk
5.7
0.95
1.4
0.3
1.2
0.12
Greasy Wool
170
0.26
15.8
28.5
1.2
0.3
Sheep - Live
34
7.0
2.3
4.0
14.4
0.4

Stubble

Product
N
P
K
S
Ca
Mg
Cu
Zn
Mn
kg per tonne
grams per tonne
Wheat
17
1.8
42
2.7
Canola
18
2.4
70
4.8
Lupins
17
0.6
26
2.7