How to...
Sampling equipment:
Soil augers are the most popular tools for sampling. Two types
are available, namely the bucket auger used for sandy soils and
the open auger, used for soils with a high clay content.
It is useful to mark the auger’s shaft in 10cm increments with
plastic tape in order to control the depth of samples taken. Use
clean, new containers for the samples as discarded fertiliser bags
or containers that contained chemicals will produce inaccurate
results. Clean paper bags are ideal as they may be placed directly
into a soil oven, when required. Seal the paper sample bags in
plastic bags so as to preserve the moisture content of the samples.
Step 2: Clear the sampling location
ff Remove loose stones and vegetation from the
sampling position without removing any topsoil
Step 3: Use the auger to take the sample
ff Note that each sample should
be taken according to the
sampling plan in terms of
location and depth
ff Place the auger in the
cleared location and turn in a
clockwise direction
ff After about 2 full turns, remove
the full auger and discard
unwanted soil
ff Continue drilling until the
required depth has been reached
Step 4: Bag the sample
Sampling Procedure
The following procedure commences after all the preparation
steps have been completed.
Step 1: Mark out the location of each sample
ff The location and depth of each sample needs to be
known prior to the commencement of sampling
ff Use the sample bag to collect the sample
ff If paper bags have been used, immediately place
them in a plastic bag to preserve the moisture
ff Continue drilling and bagging until the desired depth
of sample has been reached
Step 5: Mark the date, depth and location of the
sample on the bag
ff Marking of the samples should be done accurately
and clearly
Step 6: Submit the samples for analysis.
Sample Analysis
The reader will have realised by now that the outcome of the
analysis is totally dependent on the quality of the sampling
procedure. The following analyses are carried out on the samples
dependent on the required objectives of the investigation. The
information in this editorial has been largely based on information
obtained from the website of Bemlab (www.bemlab.co.za), which
is gratefully acknowledged
PREPARATION/
PLANNING
FERTILISATION
Particle size
analysis
Retention curve
pH
EC
Cations
Cations
pH
Phosphates
CAC
Micro elements
IRRIGATION
SCHEDULING
Water content
Useful links:
• Bemlab - www.bemlab.co.za
• Johnson’s Soil augers - www.johnsonsoilauger.co.za
• Nat. Laboratory Association of SA - www.home.nla.org.za/
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SABI | JUNE/JULY 2016