Soil

Question 1

Without soil

Answer 1

Without soil, we would not be able to grow crops and plants.

Therefore, there would be no food for animals or for people.

It is therefore a very important natural resource.

Question 2

What is soil made from?

Answer 2

Soil is made of five main ingredients.

Mineral matter
Air
Water
Living organisms
Humus

Question 3

Percentage of the main ingredients of soil

Answer 3

Mineral matter (43%)
Air (25%)
Water (25%)
Living organisms (2%)
Humus (5%)

Question 4

Soil definition

Answer 4

The layer of loose material on the Earth’s surface.

Question 5

Mineral matter

Answer 5

This is the biggest ingredient in soil. It is made o of small pieces of rocks (sand, silt, clay) broken down by weathering and erosion.

Question 6

Air

Answer 6

Air fills the spaces between the soil particles. It contains oxygen and nitrogen which are essential for plants and organisms living in the soil.

Question 7

Water

Answer 7

Water contains dissolved minerals. Plants absorb these minerals through their roots, helping them to grow. Therefore, these minerals are called nutrients.

Question 8

Living organisms

Answer 8

Earthworms, slugs, woodlice and insect and millions of micro-organisms. They break down dead plants and help to create humus.

Question 9

Humus

Answer 9

This is dark, decaying matter. It is the remains of dead creatures, plants, leaves, and grass. Humus provides nutrients to the soil.

Question 10

How soils are formed

Answer 10

Climate
Parent material
Vegetation
Living organisms
Landscape
Time

Question 11

Climate

Answer 11

Temperature and rainfall influence rate at which parent rock is broken down by weathering.

Hot climates experience chemical weathering while cold climates experience freeze-thaw.

Question 12

Parent material

Answer 12

Thpe of rock affects soil formation

Granite is slow to break down by weathering while sandstone breaks down easily and forms soil quickly

Soils that develop from limestone are more fertile than soils that develop from granite and sandstone.

Question 13

Vegetation

Answer 13

When vegetation dies it is broken down and decays to add humus and nutrients to the soil.
Deciduous vegetation provides more lead fall than coniferous.

Question 14

Living organisms

Answer 14

Micro-organisms such as bacteria and fungi help to break down the dead plant and animal life in the soil, turning it to humus.

As animals such as earthworms dig through the soil, they break it up and mix it, allowing more water and air to enter the soil.
When these creatures die their remains add nutrients to the soil.

Question 15

Landscape

Answer 15

Upland areas are cold and wet, so soils are often waterlogged. There is little pant and animal life, so there is less humus.

Lowland soils are generally deeper and well drained. They have more humus so there is plentiful plant and animal life.

Question 16

Time

Answer 16

Time is one of the most important factors in soil formation

The longer the rock is exposed to the forces of weathering the more it is broken down

It may take up to 400 years for 1cm of soil to form.

Question 17

Soil profile

Answer 17

There are a number of different layers of soil. Each layer is called a horizon.

There are three horizons, called the A, B, and C horizons. These three layers make up the soil profile.

Question 18

A horizon

Answer 18

Upper layer of soil
Darker in colour bc lots of humus
Most organisms live here

Question 19

B horizon

Answer 19

Beneath topsoil
Called subsoil
Lighter in colour bc less humus
Contains more rocks than A horizon

Question 20

C horizon

Answer 20

Parent rocj

Made from bedrock + pieces of rock

Question 21

Leaching

Answer 21

Occurs when heavy rainfall washes minerals, nutrients, humus down into B horizon

Means A horizon loses fertility as roots of plants cannot reach nutrients in B horizon

Question 22

Hardpan

Answer 22

With severe leaching, minerals can accumulate at bottom of A horizo
They are cemented together into hard impermeable crust called hard
Can cause water logging in soil above

Question 23

Brown soils

Answer 23

Formed on areas covered by deciduous forest which provide large amounts of plant litter. Litter decays to form humus.

Rainfall is limited so leaching and hardpan do not develop

Very fertile and suitable for farming

Brown in colour

Found in the dried lowlands of the south, midlands, and east

Question 24

irish soils

Answer 24

brown soils
podzol soils
peaty soils
gley soils

Question 25

Podzol soils

Answer 25

Formed on areas covered by coniferous trees, Pine needles provide limited plant litter, Plant litter decays slowly providing limited amount of humus.

Greater rainfall causes leaching, Hardpan may develop and A horizon becomes grey colour.

Podzol soils infertile, slightly acidic

Found in wetter upland areas of Cork, Galway, Wexford

Question 26

Tropical Red Soils

Answer 26

Found in regions with tropical climates with hot, wet climates

Hot, wet conditions mean chemical weathering decomposes bedrock quickly, creating deep soil cover.

Normally fertile but can become leached due to heavy rainfall, esp as result of deforestation.

Continuous leaf fall in forest which gives thick layer of plant litter, This is rapidly broken down partly by organisms and partly due to humid conditions.

Acids from decaying humus speed up the weathering of the bedrock. High temps encourage chemical actions, again causing bedrock to break down.

Weathering breaks down iron in soil into iron oxide (rust), giving soil reddish colour,

Soil is heavily leached due to very heavy rainfall.

Question 27

Soil influence on vegetation

Answer 27

Ability to retain water: Sandy soils are free-draining and support wide range of vegetation. Clay soils become waterlogged easily and are only able to support limited range of vegetation.

Fertile soils have many nutrients including nitrogen and calcium, They support wide range of vegetation, incl coniferous forests.

Acid soils lack lime: limit range of vegetation that they can support, although plants such as rhododendrons flourish.

Deep soils support vegetation with long roots such as ash. Coniferous trees, incl pine and spruce have roofs that spread outwards, so they can survive in shallow soils.

Question 28

Vegetation influence on soil

Answer 28

Provides plant litter to form humus: deciduous trees provide plentiful supply of humus, leading to brown earth soils. Coniferous trees provide limited supply of needles, leading to podzol soils.

Reduces effect of leaching: plentiful supply of plant litter ensures supply if humus, If sone leaching occurs, deep roots can bring leached materials back to surface.

Vegetation cover slows down or prevents soil erosion, Reduces impact of heavy rain on soil. Roots help bind soil particles together. When soil cover is lost, soil erosion occurs.

Question 29

Human interference with soil

Answer 29

Soil - vital natural resource

Many economic activities dependent on soil

Biggest threat - soil erosion

Main causes:
deforestation
intensive farming methods

Question 30

Deforestation

Answer 30

Conversion from forest to non-forest land

Two major effects

• Removes source of humus, loses fertility
• Leaves soil exposed to soil erosion

Solution:
forest management - controlled felling and replacing trees

Question 31

Farming methods

Answer 31

Over cropping

Overgrazing

Question 32

Over cropping

Answer 32

Crops continuously grown on land
Nutrients removed from soil
Soil becomes exhausted
Needs time to replenish
Monoculture - growth of single cash crop
Solution: crop rotation

Question 33

Overgrazing

Answer 33

Vegetation exposed to intensive grazing
Over long periods of time
Too many animals grazing an area of land
Roots destroyed
Soil left bare and exposed to soil erosion
Happened in many upland areas of Ireland