Irish Brown Earth Soils To be studied as part of Optional Unit 7 for Higher Level Leaving Cert Geography.

1. Irish Brown
Earth Soils
Geoecology

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.

18. Processes affecting formation
of brown earth soils in Ireland:
1. Humification
2. Leaching

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.