by Heinrich Viljoen
Posted on

Soil Sampling

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Soil analyses are vital to avocado management as it can give an indication of the available nutrients in the soil. Leaf analyses can give an indication of the current nutrient status of the tree.

To take a soil sample, you will need the following:

  • Wheelbarrow
  • Soil Auger
  • Clean bucket
  • Clean sampling bags
  • Labels / Marker

Procedure:

  1. Take soil samples at the same time as leaf samples (Feb-Apr) from similar soil types in the orchard.
  2. Do not take soil samples within a week of fertilising.
  3. Have the fraction sand, silt and clay analysed for every different soil type on the farm (also used to determine the soil type).
  4. Soil samples should be taken at the same indicator trees as where the leaf samples are taken.
  5. Use the same tree to take samples every year.
  6. Mark the sample trees clearly.
  7. Clear the soil from any mulch or fertiliser before the sample is taken.
  8. Take the soil sample midway between tree trunk and canopy drip line at a depth of 15 – 30 cm deep (topsoil) and 35 – 55 cm deep (subsoil)
  9. Subsoil samples are only important if acidity is suspected
  10. Always keep topsoil and subsoil samples separate.
  11. Combine at least 10 samples (from underneath 10 of the 20 leaf sampling trees) into a ± 1 -2 kg strong, clean plastic bag.
  12. Keep the sample cool and marked clearly with the farm name, reference to the orchard, sample number and sample date.
  13. Take the soil samples to the same laboratory every year and send them in for analyses as soon as possible.

Reference: R. A. Abercrombie. 2011. “Fertilization” In: The cultivation of avocado. Ed. E. A. de Villiers & P. H. Joubert. ARC-Institute for Tropical and Subtropical Crops, p. 142-144.