Soil Testing Services

The Environmental Management Agency Laboratory offers a comprehensive soil analysis lab service, utilizing Spectrophotometry, and AA equipment.

Soil Contaminants and soil pollutants like PAH's, Diesel, Petrol, Organics, Pesticides etc. can be measured via Gas Chromatography.

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Some Chemical Properties of Soil and Soil Analysis can be broken down into the following:


Acid soils are often leached of many soluble ions and are commonly deficient in major plant nutrients such as calcium, magnesium, nitrogen and phosphorus and possibly molybdenum. Phosphorus may be present in a form that is not available to plants. Metal ions may be soluble in toxic concentrations. Fungi rather than bacteria tend do dominate in acid soils.


Alkaline soils are often deficient in some plant nutrients such as iron, manganese, copper or zinc.

pH 1:5 Soil:Water

This is the activity of the negative log of the hydrogen ions in a suspension of 1:5 soil:water. pH measured in 1:5 soil:water is sensitive to seasonal variations in the pH of soil solutions.

pH 1:5 Soil:0.01 mol CaCl2

This is the activity of the negative log of hydrogen ions in a suspension of 1:5 soil:0.01 mol CaCl2. This test method is considered to approximate average soil solution calcium and salinity levels. pH in 1:5 soil:0.01 mol CaCl2 is not appropriate for soils rich in calcium carbonate.

Expected pH Buffer Capacity

pH buffer capacity is the amount of acid input required to reduce pH by one unit. Expected buffer capacity should not be used directly to calculate lime requirements nor speed of acidification. Instead, expected buffer capacity serves as a relative indicator of resistance to acidity increase between soil types.

Maximum Lime Requirement

This is an indication of the amount of lime or dolomite required to rectify aluminium toxicity/calcium deficiency problems. Lime is likely to be required if: exchangeable aluminium exceeds 5% of cation exchange capacity depending on the plants being considered; soil pH (1:5 soil: water) is <5.5 ; and

When all these conditions are met, an indication of tonnes of lime equivalents per hectare to 10 cm soil depth is given to reduce exchangeable aluminium to 5% of effective cation exchange capacity (CEC).

Required lime t/ha/10 cm = 1.3 (Exch. Al - 0.05 * CEC), where Exch. Al & CEC are me/100 g.

Organic Matter

This is based on the assumption that soil organic matter = organic carbon * 1.755. Organic matter contents are affected by climate, drainage, biological activity and landform as well as land use. Organic matter is a key component in assessing soil fertility, stability, hydrology and land condition. Total Organic Matter can also be determined by Hydrogen Peroxide digestion.

Bray Phosphorus

Bray "available" phosphorus test involves extraction of absorbed phosphorus with HCl and NH4F. Concentration of extracted phosphorus is determined by spectrophotometer.

Lactate Phosphorus

"Available" phosphorus is extracted by calcium lactate in dilute HCl and determined by spectrophotometer. Lactate phosphorus indicates probability of response to phosphorus fertilizer by wheat on neutral and alkaline soils.

This available phosphorus test is recommended over Bray phosphorus for neutral and alkaline soils.

Electrical Conductivity

Electrical conductivity indicates the amount of soluble ions (salt) in soil. Electrical conductivity is determined on a 1:5 soil:water suspension and is prepared from the fine earth fraction of the sample. As a rule of thumb, it is considered that salinity levels where yield is affected may be increased by up to 30% before a species cannot maintain an effective ground cover.


Significant hazard for iron or steel rusting in soil occurs when:

pH in 1:5 soil:water is <3.6 or pH in 1:5 soil:CaCl2 is <2.9;

clay is >35%; or

salinity is >0.8 dS/m ECe (USDA 1983).

When any of these conditions occur, "Rust" is recorded. Other significant soil conditions contributing to rust hazard include presence of sulfides and pyrite. Site conditions such as fluctuating water tables, poor drainage and intersection of several different soil materials across any iron or steel structure also contribute to rusting.

Extra care must be taken to protect buried iron or steel where a rust hazard occurs.


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