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Chapter 9 - Soil

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Miss Cummins

on 1 March 2016

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Transcript of Chapter 9 - Soil

Dark and jelly like

Forms when plants and animals decay and rot

Living organisms in soil break down the remains creating humus

Bind soil together

Provides nutrients ---> fertile soil
Soil Profiles
Horizons
Leaching
Soil Formation is influence by a number of factors
Cross section of the different layers of the soil

Surface down to the bedrock

Each layer is called a
horizon

Each horizon differs by organic content, texture and colour

Soil Types
Heavy rainfall - water passes through the soil



This washes minerals, humus and nutrients from ________ to __________?

What is it made up of ?
Mineral matter (rock)
Humus
Air
Water
Living organisms

Human Interference with Soil
What is soil ?
Chapter 9 - Soil

Thin covering of loose material
Outermost layer of the earth
It is a living thing
Why is soil important?
People need soil to grow food
Animals need plants for food
Study of soil is pedology
Mineral Matter - Rock particles
Little pieces of rock
Created from weathering and erosion
Contain minerals which help plants to grow
Interesting facts about soil
Almost all the food you eat, material for clothes and wood you burn is produced by soil
A single shovelful of soil can contain more species of organisms than live above ground in the entire amazon rainforest
When you take a step in a forest, you are being held up on the backs of thousands of bugs
Main ingredient in soil
Stones, sand, silt, clay
Particle size Name Character
Large Sandy Space for air/drainage
Small Clay Holds moisture
Small Loam Mix of clay and sand
Humus
Dark, jelly like substance
Forms when plants and animals decay and rot
The living organisms break down the soil
Binds the soil together
Provides nutrients that make the soil fertile
Air
Fills spaces between rock particles

Contains oxygen and nitrogen - vital for plants to grow and for living organisms to survive in the soil
Water
25% of soil

Helps bind it together

Minerals dissolved in water are absorbed through roots

Helps plants to grow
Living Organisms
Soil is home to many living things

Earthworms, bacteria, fungi, insects and burrowing animals

These organisms break down the organic matter to form ______?

Make easier for water and air to pass through
http://lifeunderyourfeet.org/en/soileco/intro/biodiversity.asp
O horizon
Contains organic matter

Leaves and decomposing vegetation are called plant litter

This provides humus for the soil
A horizon
Upper layer of the soil
Topsoil
Most organisms live here
High humus content
Usually darker than other layers
Most fertile part of the soil
B horizon
Subsoil
Lighter colour than the A horizon - less humus
Located near the bedrock - more stones and is protected by weathering and erosion
C Horizon
Bedrock or parent material
Lower layer is solid rock
Upper section may be broken up into rock particles
A horizon B horizon
Most plant roots are located in the ___________






This means that leaching can interfere with the growth of roots, if their nutrients are washed beyond their reach
A horizon
Sometime, in extremely wet conditions, minerals can build up at the bottom of the A horizon
This creates a HARDPAN
This is an
impermeable
layer --> soil above the hardpan becomes waterlogged
Q. If some thing is impermeable, what does that mean?
That liquids can not pass through it
Shale, marble, mud stone, slate and well-packed sandstone are examples of impermeable rocks
Question for homework
Explain the term leaching. How does leaching have a negative impact on vegetation growth?
These factors include:
Climate
Living Organisms
Landscape
Vegetation
Time
Parent material
Climate
Parent rock is broken down by weathering - this depends on the temperature and the amount rainfall
Freeze thaw action occurs in areas with cold climates
Chemical weathering occurs in areas with a hot climate
Freeze thaw action
Chemical weathering ?
This is when rocks are dissolved because of a chemical reaction
Example?
Carbonation
Weak carbonic acid in rain weakens rock - limestone (contains calcium carbonate)
Carbon acid and calcium carbonate react and dissolves it
Parent Material
This is bedrock that is broken down from weathering to form soil

Minerals from broken down rock = nutrients

Living Organisms
Bacteria and fungi

Break down into ___________ in the O horizon ---> this then creates ________ which makes the soil fertile
Animals such as earthworms and burrowing animals break up the soil - this allows for the movement of ______ and ______ through the soil
When these organisms die they add nutrients to the soil
plant litter
humus
water
air
Landscape
Soil in upland areas are usually thin due to ______________ and are badly drained due to increased rainfall in upland areas
Soils in lowland areas are usually deeper and well drained

This means the soils are more __________
They are rich in humus, why?
More plant litter and living organisms
fertile
mass movement
Vegetation
Vegetation provides humus which makes soil fertile
Areas with deciduous trees have more plant litter than coniferous
Provides nutrients for the soil
Time
It can take up to 400 years for __cm of soil to form

Weathering process is slow

The longer rock is exposed, the more it is broken down
1
Homework question
Explain how THREE different factors influence the formation of soil
What were the four soil types mentioned in the map?
Brown earth soils
Peaty soils
Podzol soils
Gley soils
Brown soils
Most common in Ireland
Mostly found in lowland areas - midlands
Developed on boulder clay which was deposited at the end of the last Ice Age
Deciduous forests develop on brown earth soils
Plant litter - from leaves that have fallen - create material for humus
This is why the soil is so dark
Very little leaching occurs
Soil is very fertile
Overtime forests were cleared for agricultural land
This land is now used for intensive arable and pastoral farming
Intensive

Very thorough or vigorous
Arable
Crops
Pastoral
Animals
Farmers add nutrients to the soil in the form of _______ and _______ because of plant litter is no longer as high as it was when these soils were formed
manure
fertilizers
Podzol soils
Found on floors of coniferous forests in cold and wet areas
Very little plant litter and very little humus, why ?
The cold and damp condition means there is very little . . .
High levels of leaching - nutrients washed through A horizon often creating a ________
hardpan
This results in the A horizon being very grey in colour
Podzols are relatively ______ and acidic
infertile
Podzol soils are found in poorly drained upland areas in Galway and Cork
Gley Soils
Guess what colour they are ???
GREY
Difficult land to cultivate
Only used for _________ farming
Develops where bedrock or clay above it is impermeable
Sticky and waterlogged
pastoral
Peaty Soils
Dark in colour
Develop in cold, upland areas with high rainfall AND low land areas with poor drainage
Peaty soils are:
Waterlogged
Full of organic matter that has not broken down
Valuable source of fuel
Found in blanket and raised bogs
Question for homework
Tropical Soils
Tropical red soils are found in areas with hot and wet climate conditions
Usually in the tropical or equatorial zones such as the Amazon Basin
https://quizlet.com/123225317/flashcards
Two types of bogs?
Blanket
Raised
Mountainous
Lowlands
Shallow
Deep
Wicklow Mts
Bog of Allen
High temperature and heavy rainfall cause intense
chemical weathering


This leads to the formation of a very
deep
soil
There is a constant supply of
humus
due to
rapid
vegetation growth and
continuous leaf fall
throughout the year
High temperature also gives rise to
rapid

breakdown
of
plant litter
by living organisms in the soil
The soils gets is reddish colour because of its high
iron
content
This is increased by the high levels of
acidity
from the decaying humus
Chemical weathering causes the bedrock to
break down
Leaching occurs due to ____________
heavy rainfall
Tropical soils are very
fertile
and produce a
lush
vegetation cover
BUT, the supply of humus is decreased when the
forests are cut down
When deforestation occurs, the soil is left
unprotected
and
leaching
increases

This then causes the soil to loose its
fertility
Natural Vegetation and soil
What is natural vegetation?
Any plant/tree that grows on their own '
naturally
' without human interference
The natural vegetation of a region depends on its _______________
climatic conditions
The type of vegetation varies according to soil conditions and soil conditions are in turn influenced by the vegetation growing on them
The influence of
soil
on vegetation
1. Deep fertile soils have the ability to support a
wide variety
of vegetation because they have a high nutrients content
2.

Shallow

infertile soils are more limited in the type of vegetation that they are able to support.


Coniferous
forests are often planted in such areas.
Soil influences the type of vegetation that grows in it a number of ways:
3. Some plants, such as
rhododendrons
, grow in areas with
acidic soil
. However, the range of vegetation can be limited in these areas. Farmers spread
lime
on the soil to reduce its
acidity
and make it more fertile.
4.
Clay soils
can become
waterlogged
easily and farmers find it
difficult to cultivate
them
5.
Sandy
soils are
free-draining
and have the ability to support a
wide range
of vegetation
The influence of vegetation on soil
Vegetation also has an important influence on soil
1. Vegetation provides the
plant litter
to make humus
Brown earth soils are formed in _________ forests rich in humus and are very _________
Whereas, podzol soils formed under __________ forests are _________
deciduous
fertile
coniferous
infertile
2. Vegetation
binds
the soil and protects it from the
soil erosion and mass movement
. When this cover is lost, the soil is
vulnerable
and erosion occurs.
---> When leaching does occur, for example in tropical rainforests - some trees have very
deep
roots in order to access the nutrients which are
transported
down
3. Vegetation acts as an
umbrella
and reduces the impact of heavy rain on soil - this then reduces the effects of leaching
Soil is a vital natural resource
Many economic activities are dependent on it

Soil is often over-exploited
What are the main ways that humans interfere with soils?

Deforestation and Farming methods
Deforestation
Conversion
from forest to non-forest

It's the removal of trees for
economic
and
agricultural
uses
This has two major effects:
1. The removal of vegetation also
removes
the
source
of humus from plant litter, which means that the soil loses some of its
fertility

This lack of vegetation cover can lead to
flooding
in lowland areas and
mass movement
in upland areas during periods of heavy rainfall
2. The removal of vegetation cover leaves the soil
exposed
to wind and rain - this causes
erosion
Solutions
Forest management

Control felling

Replace felled trees - reafforestation
Farming Methods
1. Over cropping
The soil looses its
fertility
and becomes
exhausted

Soils need a chance to recover and
replenish

This is when crops are
continuously
grown on the land
Nutrients
are constantly being
removed
from the soil
Monoculture
Monoculture is the growth of one
single
crop type - usually a cash crop
The
same
nutrients are taken from the soil over and over again
Soil then becomes
infertile
Practiced in many areas, especially
poor
countries
Cash crops
2. Over Grazing
Overgrazing is when vegetation is exposed to intensive grazing for long periods of time
Or when too many cattle/sheep graze in an area of land
Roots are destroyed and the soil is left bare and exposed to wind and rain ---> soil erosion
Revision Time
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