Soil sampling

1
Soil sampling

• Bruce Ball
• Crop and Soil Research

2
Sampling location

• Subdivide the soil across the landscape into
  classes that are fairly uniform - often single
  field
• - take guidance from soil maps, changes in
  vegetation and topography
• Avoid areas near fences, gates, water troughs and
  spillages
• Sample each uniform area in a W pattern

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Sampling location
4
Sample number

• Take 5 - 10 samples from each location and bulk
  by mixing in a bucket and subsample, or bulk and
  use the whole sample
• If the uniform area is bigger than 1 ha, more
  samples are required.
• Normally about 1 kg of soil is plenty for routine
  soil analysis
• Systematic grid sampling is required if you want
  to pick up a suspected concentration gradient

5
Sample depth

• For fertility assessment, this is the normal
  ploughing or digging depth (0-25 cm) (remove
  surface vegetation before sampling)
• For soil biological factors, sample near the
  surface
• Assessment of compaction and water movement may
  require sampling below 25 cm depth

6
Sampling tools

• A trowel of spade can be used, but this causes a
  lot of soil disturbance and can be difficult to
  get depths correct.
• Dutch auger - useful for loose, dry and stony
  soils
• Screw or spiral auger - easy to use, but can lose
  dry soil and be held up by stones
• C-section auger - good for discriminating depths

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Auger types - from Eijkelkamp catalogue
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Other sampling protocols

• Keep augers clean
• Collect soils in poly bags
• Label these before going to the field
• Routine fertility samples need not be dried or
  kept cool
• Samples for mineral nitrogen need to be kept cool
  and sent for analysis within 24 h or frozen

9
General point

• Soils are highly variable - it is better to
  sample a few properties at many locations than
  many properties at few locations.