2. Exam Brief
Typical Exam Question:
“Examine the development of an
Irish soil that you have studied.”
3. Irish Soils
Despite
its small size, Ireland has a variety
of soils.
Brown earths are the most common soil
type.
They are mainly found in the centre of
Ireland.
4. Irish Soils
There are 4 main types
of soil in Ireland:
1.
2.
3.
4.
Brown soils
Podzol Soils
Peaty Soils
Gley Soils
5. Soil Profile:
Brown Earth Soil
No
distinct horizons –
uniformly brown in
colour.
This is due to the climate
which encourages the
presence and activity of
worms and beetles in
the soil.
These mix the soil up
and remove any
horizons that may form
due to leaching and
humification.
6. Factors influencing brown
earth soils in Ireland:
Climate
Relief
Living
organisms / vegetation
Parent material
Time
7. Climate
Brown
earth soil has developed in response to
Ireland’s cool maritime climate.
Temperature averages 15ºC in July to 6ºC in
January.
Soil temperature rarely cold enough to stop
biological activity completely.
Rainfall average 1500 mm per year.
Climate encourages year round
bacteria, earthworm and fungi activity.
Brown earth soils are found where soil
temperatures are above 0ºC for 9 months of the
year.
8. Relief
Relief
influences (1) depth and (2) drainage of this
soil.
Brown earth soils formed on slopes tend to be
thinner and well drained - mass movement
creates deep soils at the base of slopes.
In soils formed on colder higher ground there is
less animal activity and less humus is formed than
in soils formed on warmer lowlands.
Aspect: South-facing slopes have warmer soils
than north-facing so agriculture is often possible
on slopes with a southerly aspect.
9. Living organisms / Vegetation
• Brown earth soils develop under deciduous forests
(e.g. oak, ash, chestnut, birch).
• The top horizon has a thick layer of dark rich
humus due to the accumulation of leaves during
autumn.
• Due to the mild climate micro-organisms such as
bacteria and fungi are active for at least 9
months of the year adding to the fertility of soil.
• Animals like badgers and rabbits burrow into the
soil, churning it up and removing horizons.
10. Parent Material
The
parent material, or bedrock, is usually
boulder clay deposited during the last ice age.
Local changes to parent material have
created three variations (intrazonal) in brown
earth soil:
A.
B.
C.
Acidic brown earths – 500m above sea level on
crystalline rock (e.g. granite, sandstone)
Shallow brown earths – in limestone areas such
as Burren
Podzols – slightly leached, occur on glacial drift
of Irish lowlands.
11. Time
These
brown earth soils have
developed since last ice age
over 10,000 years ago.
They are mature, well
developed soils but have local
variations depending on
slope, aspect and drainage.
12. Characteristics of brown earth
soils in Ireland: COLOUR
Brown
in colour due to:
Presence
of humus which makes it
appear dark.
Action of leaching which washes
some nutrients out of soil so that it is
not too dark brown in colour.
13. Characteristics of brown earth
soils in Ireland: pH
Varies
from slightly alkaline to
slightly acidic due to temperate
climate and variations in parent
material.
Living things thrive in this pH.
14. Characteristics of brown earth
soils in Ireland: Humus Content
Brown
earth soils are rich in
humus because the natural
vegetation in Ireland is
deciduous forest.
15. Characteristics of brown earth
soils in Ireland: Structure
Brown
earth soils have a well
developed crumb structure that
provides pore spaces for air and
water, encouraging plant
growth.
16. Characteristics of brown earth
soils in Ireland: Texture
Generally
have a loam texture
due to presence of variety of
parent materials (e.g. sandstone
and shale).
17. Characteristics of brown earth
soils in Ireland: Water Content
Depends
on local conditions of
relief and drainage.
Because of its generally loam
texture and crumb
structure, these soils are not too
wet or dry.
They have a water content that
encourages plant growth.
19. Humification
Cool
temperate oceanic climate
encourages humification all year long.
Rate of humification:
Decreases in winter
Speeds up in summer
The
presence of large amounts of humus
adds to soil’s fertility.
20. Leaching
Year
round rainfall
causes moderate
amounts of leaching in
brown earth soils.
This adds to soil fertility by
gently washing nutrients
down to the soil.
Waterlogging can occur
in poorly drained areas
causing brown earth soils
to become gleys.