Brown Earths
Geoecology section
Draw, colour and label a soil profile of brown earth soils.
(soil type named = 4marks, soil profile = 4marks)
List the 5 factors influencing the formation of brown earth soils in
Ireland? (Each factor named = 2m = 10 marks)
Write three key points for each factor? (5 factors x 3 details = 15 srps =
30 marks) ********if you have extra details use them
Describe the appearance of the soil profile. (characteristics)
The colour/texture/pH, humus etc – 2 main descriptions of each horizon.
(name of horizon= 3 x 2m, description= 3 x 4m= 12 marks)
Name and explain the uses of and locations of brown earth soils in
Ireland or elsewhere. (types of agriculture etc)
Details on Brown earth soils:
• Factors influencing brown earth soils
in Ireland.
• Describing the soil profile and
characteristics of brown earth soils.
Climate of Ireland: Cool, temperate oceanic climate (6-15C, 7501500mm rainfall per year average)
Natural vegetation: mixed deciduous forest
Zonal soil: Brown earth soil
(note higher rainfall and small climate variations in Ireland sees a
difference in the water content and pH of some Irish soils)
Factors influencing brown earth soils:
• Climate
• Relief
• Organisms / Vegetation
• Parent Material
• Time
1. Cool temperate oceanic climate.
2. 6 – 15 C temperatures average.
3. Mild conditions favour biological activity all
year round.
4. Bacteria and fungi examples of micro organisms
active in Ireland.
5. Average rainfall in some areas of 1500mm.
6. Brown Earth soils found in areas with temps
above 0degrees for at least 9 months a year
1. Relief influences depth and drainage of the soil.
2. BES found on slopes are thinner and well drained due to soil
creep and gradient.
3. Deeper soil at bottom of slope due to soil creep or other type of
mass movement.
4. Relief important for temperatures. Higher altitude : lower
temps : less biological activity.
5. 1 degree drop per 100m climb.
6. Less animal activity on higher ground : less humus /
humification.
7. Aspect important: north facing slopes colder and less biological
activity so……
1. Natural vegetation: mixed deciduous forest.
2. Main varieties include: oak, ash and chestnut.
3. Deciduous trees lose leaves in winter : plant matter for
humification.
4. Presence and activity of micro organisms all year round: all year
round humification.
5. Burrowing animals increase mixing of humus and soils
increasing fertility.
6. Animals such as badgers, hedgehogs and rabbits dig burrows
moving material from surface into lower horizons.
7. Movement and mixture of plant material and humus gives soil a
general brown appearance and less obvious horizons.
1. Last ice age ended in Ireland approx 10,000
years ago.
2. Therefore soils tending to be approx this age.
3. Soils are mature but have local differences due to
slope/climate changes etc.
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Parent material generally refers to underlying rock of soil.
This is generally the source of minerals for soil as rock is weathered.
Some parent material in Ireland as result of glacial deposition.
This parent material is boulder clay (a mixture of clays and stones).
Three main variations in brown earth soils in Ireland:
Acidic brown earth soils – found in areas above 500m.
Generally lie above rocks with high crystal content like granite or sandstone.
Acidic brown earth soils can be found in Comeragh mountain areas of
Waterford.
Sandstone rock underneath.
Shallow brown earth soils – high in calcium.
Found in limestone areas.
Also known as Rendzina soil.
Found in Burren, Co. Clare.
Podzolised brown earth soils are slightly leached.
Found in areas of glacial drift.
22% of country covered in Podzolised brown earth soils.
Found in and around Dublin area.
The A horizons of these soils are a pale grey colour.
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Crumb texture
Well drained
Slightly acidic
Dark brown colour
Very fertile
• O Horizon; lot of organic matter, many animals
(slugs, worms) and micro organisms (fungi,
bacteria).
• A Horizon; much humus, dark brown colour.
• B Horizon; subsoil, light brown.
• C Horizon; bedrock.
• Brown soil
• Colour due to presence of humus
• Leaching washes some colour down through soil
• Ranges from slightly alkaline to slightly acidic.
• Changes due to temperature changes, rainfall differences and
underlying rock around the country.
• Ideal pH range for bacteria.
• Bacteria, fungi, organisms increase fertility by digging,
decomposing.
• Year round bacterial activity due to temperatures usually above
freezing point.
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Rich in humus
Natural vegetation of Ireland is deciduous forests
Leaves add humus to soil
Decomposed by organisms
• Loam texture (mixture of clay and sand)
• Texture due to erosion of sedimentary rocks and spreading of
river alluvium.
• Crumb structure
• Large air pores for air and water
• Useful soil for tillage and pastoral farming
• Depends on local relief and drainage
• Not too wet or dry due to structure and texture
• Water content of brown earth soils encourages plant
growth
• Cool temperate oceanic climate provides 500-2800mm
rainfall per year on average.
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Fertile soil due to humification
Decreases in winter due to lower temperatures
Increases spring/summer due to higher temperatures
Deciduous forests adds plant matter to soil for this process.
Ideal temperature range for bacterial activity all year round.
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Rainfall all year round
Moderate amount of leaching
Washes nutrients down through soil
Waterlogging in some areas can cause brown earth soils to
become gleys.
• Cultivated for centuries
• Now nourished with artificial fertilisers, manure and lime
• Suitable for wide range of agriculture, tillage, pasture and forestry.