Soil Classification

Soil Classification

• Soil Types
  There are about 35 general soil groups in the world.
  Only 10 are found in Ireland:-
  1.Podzols
  2.Brown earths
  3.Gleys
  4.Basin peats
  5.Blanket peats
  6.Regosols
  7.Brown podzolics
  8.Grey brown podzolics
  9.Rendzinas
  10.Lithosols

 

• Podzols- 6.8% of country usually in mountains and hills.
  On top of acid parent material and have very low pH.
  Leached of nutrients and of little ag. value except for forestry.
  Can get an iron pan in B horizon which stops water flowing down causing a blanket peat to form on top. These soils are typical of areas where the parent rock is acidic (like granite) and the annual rainfall is quite high (> 1000 mm) and a moderate, cool climate.
  These soils show serious cases of leaching of both mineral and humus.
  These materials are translocated into the B Horizon.
  This process is caused PODZOLISATION.
  When serious cases occur and large amounts of iron oxide (rust) have been leached from the A horizon into the B horizon, an iron pan may form when these cement together.
  This in turn causes major problems for drainage and root penetration.
  If water logging or flooding occur, then little or no oxygen will be available and organic matter will eventually form an O Horizon.
  This is the first stage of a formation of a peat and the soil is now known as a Peaty Podzol.
  When the O Horizon becomes deeper than 30 cm, then the soil is no longer podzol, but is now a blanket peat.
  Podzols are not very useful as tillage soils, or for grazing. This is due to their poor drainage and poor root penetration.
  In cases where Iron Pans have not formed, Podzols may be useful for Forestry.
  Podzols must be managed carefully or they may very quickly become unsuitable again.


• Acid Leaching
  Rainfall is high and parent material is acid.
  Soluble nutrients are carried down in acid percolating water.
  The soil becomes leached of bases (Mg++, Ca++) and gradually becomes more acidic.
  The clay, humus and nutrients that are leached build up in the B horizon.


• Brown Earths
  12.6% of the country mainly in areas of low rainfall and on top of lime rich parent material.
  No distinct horizons
  Texture, structure and drainage suitable for arable farming.
  Best agricultural soils.

These soils are mature, well drained mineral soils.
They have not suffered from serious cases of leaching (loss of minerals)
They have a uniform profile (i.e. No distinct horizons or layers)
The Brown Earths in Ireland are mainly found in areas where the underlying rock is acidic, and therefore the soil is acidic.
With regular liming and fertilising the soils can be quite a productive soil. Occurs where rainfall is low and parent material contains a lot of calcium.Where these soils have deciduous forest or grassland growing on them they recycle bases and acidification is prevented.This results in deep, humus rich soils with little horizonisation, that are moderately base rich and fertile.

• Gleys
  27.5% of the country either in depressions (surface water gleys) or over impervious layers (ground water gleys).
  Wet, badly structured and short growing season.
  A horizon is moderately structured with some biological activity. B horizon is mottled grey/blue colour.
  Poor soils but can be improved by drainage.


• Gleisation
  Independent of rainfall and parent material.
  Caused by water-logged conditions.
  Leaching does not occur but anaerobic conditions lead to the iron in soil becoming reduced (no oxygen) and turns blue.