Deciduous forests developed on this soil, and the plant litter from the leaves that fell from the trees every year provided material for the formation of humus. This is why brown earth soil has a dark colour. Very little leaching occurs in these areas, so the soil remains fertile.
Over time, the forests were cleared for agricultural land. The land is now used for intensive arable and pastoral farming. Farmers add nutrients to the soil in the form of manure and fertilisers because the level of plant litter is no longer as high as it was when these soils were formed.
Deciduous tree
Thick litter (especially in autumn after leaf fall)
O-horizon
A-horizon
B-horizon C-horizon
Weathered parent material
: Figure 16.11 Soil profile of a brown earth soil
Podzol soils
Podzol soils are found on the floors of coniferous forests in cold and wet areas. Coniferous forest floors have little plant litter, and therefore small amounts of humus. The cold and damp conditions mean that there is also little earthworm activity.
Heavy rainfall causes a lot of leaching, and nutrients are washed through the A horizon, often creating a hardpan. This gives the A horizon a grey colour.
Podzols are quite infertile and acidic. They tend to be heavy soils and their texture has more clay particles than sand and silt. They are found in poorly drained upland areas of Co. Galway and Co. Cork.
Coniferous trees
O-horizon A-horizon
B-horizon
C-horizon : Figure 16.12 Soil profile of podzol soil
