Chapter 9 - Soil Flashcards
Describe the composition of soil. Include percentages
- Water 25%
- Air 25%
- Living organisms 2%
- Mineral matter 43%
- Humus 5%
Describe the composition of soil mineral matter
This is the largest ingredient in soil. It is made up of small pieces of rocks (sand, silt, clay) broken down by weathering and erosion
Describe the composition of soil air
Air fills the spaces between the soil particles. It contains oxygen and nitrogen which are essential for plants and organisms living in the soil
Describe the composition of soil water
Water contains dissolved minerals. Plants absorb these minerals through their roots, helping them grow. These minerals are called nutrients
Describe the composition of soil, living organisms
Earthworms, slugs, woodlice, insects and millions of microorganisms breakdown plant matter into humus
Describe the composition of soil, humus
Dark, decaying organic matter. It is remains of dead creatures, plants, leaves and grass. Provides nutrients for the soil
What is soil?
Soil is the thin covering of loose material that makes up the outermost layer of the planet
What are the four soil horizons?
O horizon (plant litter) A horizon (top soil) B horizon (subsoil) C horizon (bedrock)
O horizon
Plant litter
-> Layer of vegetation
A horizon
Topsoil
-> Contains humus so is dark in colour. In wet conditions, minerals in this horizon can be leached (washed downwards) to B horizon. A hardpan layer of leached material may form which is impermeable
B horizon
Subsoil
->Light in colour because there is less humus. More stoney
C horizon
Bedrock
-> Parent material
What are the factors that affect the formation of soil?
○Climatic conditions ○Parent material ○Vegetation ○Living organisms ○Water ○Time
What are the three types of soil textures?
Sandy
Clay
Loam
Describe sandy soils
►Light, dry, gritty
►>70% sand -> well drained
►Drainage can cause soil to loose nutrients and suffer during drought
Describe clay soils
►Heavy texture -> clay particles prevent water passing through -> waterlogging
►Difficult to plough
►Best for pastoral farming (growing grassland for animals)
Describe loam soils
►Mixture of sand and clay ►Well drained ►Retain minerals ►Well aerated ►Suitable for crop farming and gardens
Describe brown earth soils
- Formed in areas with deciduous forests -> lots of rotting vegetation
- Precipitation is low -> little leaching
- Dark in colour because of rich organic humus
- Creates a fertile topsoil which is good for crops
- Most common soil in Ireland
Describe peat soils
- Dark
- Develop in mountain and low-lying regions with poor drainage
- These areas are waterlogged and lack oxygen
- Micro-organisms which normally break down decaying vegetation cannot exist without oxygen
- Peat consists of layers of partially rotted vegetation
- Although it is rich in humus, it is infertile because it is waterlogged
- Valuable fuel
Describe podzol soils
- Developed in cold and wet areas covered in coniferous forests
- Pine needles provide little plant litter
- Heavy rain leads to leads to leaching and hardpan
- Low in humus so is relatively infertile and acidic
- Podzols are found in poorly drained upland areas of Galway and Cork
Describe gley soils
- Grey in colour
- Develop where soil or bedrock beneath is impermeable, e.g. shale and clays
- Sticky and waterlogged
- Limited fertility due to poor drainage
- Used for pastoral farming
Describe Latosols/Tropical Red Soils
- Red soils found in tropical climatic regions
- Is hot here all year round
- Forests around equator have high temperatures and humidity so decaying organic matter is being broken down into humus at a fast rate
- Leaching
- Within the soil all minerals are leached except iron
- The iron rusts and turns red when exposed to oxygen, giving the soil its colour
What are the four main soil types found in Ireland?
- Brown earth soils
- Peat soils
- Podzols
- Gley soils
What are the main types of soil erosion?
- Deforestation
* Intensive farming methods
Deforestation
The cutting down and clearing away of trees and forests
What is the solution to deforestation causing soil erosion?
Forest management and reaforrestation
What is overcropping?
Occurs when crops are continuously grown on the land
What is monoculture?
Means planting the same crop over and over again
What is overgrazing?
Occurs when vegetation is exposed to intensive grazing for long periods of time or when too many animals graze on one are of land
