Test Methods

As a Member of ASPAC, SWEP uses laboratory methods included in their accreditation program. For further details, see the technical reference below.

Analytical Methods for Soil:

• pH and Electrical conductivity (5:1 water) - methods 4A1 & 3A1
• pH Calcium Chloride - method 4B1
• Exchangeable cations (Ca, Mg, Na, K) Ammonium Acetate - method 15D3 or 15C1
• Exchangeable Hydrogen - Barium Chloride-Triethanolamine method*
• Nitrate Nitrogen - Calcium Chloride-Brucine method (colorimetric)
• Available Phosphorus - Olsen extractable, method 9C1
• Available Potassium - Ammonium Acetate, method 15D3 or 15C1
• Available Sulphur - Ammonium Acetate
• Available Cu, Zn & Co - EDTA method 12B1
• Available Fe, Mn - method of E.H. Mikhail (1981)
• Available Boron - Hot Calcium Chloride, method 12C2
• Available Molybdenum - Ammonium Oxalate-Oxalic acid-di-iso propyl ether (Graphite furnace)
• Total Organic Matter - modified Walkley & Black, method 6A1
• Extractable Silica - Dithionite-Citrate method**

NB. For available Iron and Manganese, SWEP uses the method developed by E.H. Mikhail (1980) due to the tendency for the standard EDTA method to produce erroneously high results.

Analytical Methods for Water:

• pH and EC - methods C1a and B1a
• Total Soluble Salts - method B1b
• Soluble Cations (Ca, Mg, Na, K) - methods L1b, L2b, L3b, L4b (Strontium Chloride releasing agent, AA by direct aspiration)
• Nitrate Nitrogen - Brucine colorimetric method (UV by direct aspiration)
• Phosphorus - Ammonium Molybdate-meta Vanadate (UV by direct aspiration)
• Sulphur - method J2a (ICP direct aspiration)
• Total Cu, Zn, Mn - method K1a (AA by direct aspiration)
• Total Fe - method K2b (AA by direct aspiration)
• Total Boron - method J2a (ICP direct aspiration)
• Total Cobalt - Graphite furnace AA by direct aspiration
• Total Molybdenum - Graphite furnace AA by direct aspiration

Analytical Methods for Plant Tissue:

Total Nitrogen - Dumas method (TruSpec CN).

All other elements (total) - Acid digestion.

Analytical Methods for Soil Biology:

Our Microbiology Lab uses a detergent solution to extract organisms from the soil sample, followed by x10 stepwise serial dilution, prior to plating of the cultures. Each of the cultures is duplicated and the results from each duplicate set averaged and calculated back to cells/ gram of dry soil to produce the results.

Both Aerobic and Anaerobic cultures are used:

Aerobic cultures:

• Yeast⁴ - MYA2 (malt/yeast extract agar)
• Fungi^{1, 3, 4} - CZA (Czapek-Dox agar)
• Cellulose utilisers^{1, 2} - Cellulose agar (minerals + cellulose powder)
• Actinomycetes² - Waksman medium
• Anaerobic cultures:
• Lactic acid bacteria - Vitamin B12 production medium
• Photosynthetic bacteria² - Minerals + Glycerol agar

References:

* Peech, M., Cowan, R.L. & Baker, J.H. (1962) Soil Science Society American Procedures, A critical study of the Barium chloride-Triethanolamine and ammonium acetate methods for determining exchangeable Hydrogen of soils.

** Ross, G.J. & Wang, C. (1993) Soil Sampling and Methods of Analysis, CRC Press, Boca Raton, Florida, USA.

For numbered soil test methods:

Rayment, G.E. & Higginson, F.R. (1992), Australian Laboratory Handbook for Soil and Water Chemical Methods. Inkata Press, Port Melbourne, Australia.

For Soil Biology methods:

1. Germida, J.J. (1993) Culture Methods for Soil Microorganisms; in Carter, M.R. (ed.) Canadian Society of Soil Science - Soil Sampling and Methods of Analysis. Lewis Publications.
   
   
2. De Ley, J. et al (eds.) Culture Collection of the Laboratorium Voor Microbiologie - Bacteria 1989.
   
   
3. Nolard-Tintigner, N. et al (eds.) Culture Collection of the Institute of Hygiene and Epidemiology - Mycology 1989.
   
   
4. Hennebert, G.L. et al (Eds.) Mycotheque de l'Universite Catholique de Louvain - Fungi-Yeasts 1989.