4th meeting of the Global Soil Laboratory Network (GLOSOLAN) 11-13 November 2020 Mr. Rob de Hayr

1. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Rob De Hayr GLOSOLAN Vice-Chair
Item 18: Endorsement of the units of
measure to use in GLOSOLAN SOPs

2. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
SI Units

3. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)

4. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
SI Prefixes

5. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Non-Si units accepted for use
with SI units

6. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Other Conventions
• Kilogram is the only coherent SI unit formed by attaching
prefixes to the unit name “gram” (e.g. 10-6 kg is written mg
not µkg)
Soil Chemistry Conventions
• Derived units are traditionally chosen:
• the scale of the value can be easily comprehended
and interpreted (e.g. 5 mg/kg not 0.005 kg/kg)
• easily compared with historical data
• Parameters are represented in their equivalents where
summation or comparison is required (e.g. cations)
• Units required by Journals and other publications

7. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Guidelines for reporting soil chemical results
Method or property Units
EC of 1:5 soil/water and saturation extracts dS/m
Soil pH, including delta pH nil
OC (Walkley and Black & Tyurin)
Total carbon & total organic carbon (Dumas – dry combustion)
g/kg
Total N (Dumas, Kjeldahl N) g/kg
Mineral Nitrogen (Nitrate-N & Ammonium-N)
mg (element)/kg
Extractable P (Olsen, Bray I & II)
Available micronutrients (Fe, Zn, Cu, Mn, B, Mo, S, K) Various extractants
Mehlich 1 & 3 extractable elements
Exchangeable bases (Ca, Mg, Na, K)
cmol(c)/kg
Exchangeable acidity, Al and H
CEC, ECEC and AEC
Soil carbonate/s (laboratory) % CaCO3 equiv.
Soil carbonates (field) % CaCO3 equiv.
Moisture contents and Loss-on Ignition g/kg
Particle Size (clay, silt & sand) g/kg
Bulk density g/cm3
Total and acid digestible elements (metals, rare earths, trace elements) mg/kg or µg/kg
depending on the
concentration of
the element

8. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Some Conversions
multiply bey the numbers in
the table to get these units
dS/m cmol(c)/kg
S/m 10
mS/m 0.01
µS/m 10-5
mS/cm 1
µS/cm 10-3
mmol(c)/kg 10
meq/100g 1
Calculation of centimole:
= atomic weight / number of charges / 100
To convert mg/kg to cmol(c)/kg to for the
individual cations, mg/kg is divided by the
following numbers:
Calcium 200
Magnesium 120
Potassium 390
Sodium 230
Aluminium 90
GLOSOLAN will provide conversion tables
GLOSOLAN will adapt already published SOPs to the agreed units of measure
New GLOSOLAN SOPs will be written accordingly.

9. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Number of significant figures to use:
it depends on the method and equipment
Not defined, OPEN!

10. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Another thing we should decide upon
is on how to report the units…
e.g. g/cm3 or g cm-3

11. 4th Meeting of the Global Soil Laboratory Network (GLOSOLAN)
Thanks for your attention