Please enable JavaScript.
Coggle requires JavaScript to display documents.
Physical Properties of Soil - Coggle Diagram
Physical Properties of Soil
Soil Composition
Mineral Matter
Derived from Parent Material of the soil
Organic Matter
Dead plants decompose to form humus which contribute to soil structure and fertility
Air & Water
The pores between soil particles have air and water in them. The proportion of air and water depends on rainfall, temperature and evaporation
Soil Particles
There are three main particles sand,silt & clay
All 3 are usually present in the soil, the proportion determine many soil properties
There are pores between the particles. The size of the pores determine the size of the soil
Sand Particles
Sand is the largest particle and so the pore spaces between the particles are large. This makes it easier for water to pass through the soil and allows for good drainage
However, in times of low rainfall sandy soils are more susceptible to air times of high rainfall sandy soils are less likely to waterlog
As air heats up quicker then water, sandy soils warm up quickly
Sand particles does not contribute to fertility
Clay Particles
Clay is the smallest particle and so the pore spaces between the particles are small. This makes it difficult for water to pass through the soil. This means there is no water logging
In times of low rain rainfall clay soils are less likely to suffer from drought. In times of high rainfall clay soils are more likely to suffer from waterlogging
As water does not warm up as fast as air, clay soils warm up slowly
Clay particles contribute to soil fertility
Clay VS Sand Particles
Clay
Particle Size: Small
Pore Size: Small
Drainage: Poor
Aeration: Poor
Low Rainfall: Drought resistant
High Rainfall: Prone to Waterlogging
Fertility: Contributes
Sand
Particle Size: Large
Pore Size: Large
Drainage: Good
Aeration: Good
Low Rainfall: Prone to Drought
High Rainfall: Resistant to Waterlogging
Fertility: Not Contributing
Soil Texture
Soil Texture
Proportion of sand, silt and clay particles in the soil
Loam
Roughly even parts of sand, silt and clay
Influences the aeration, drainage, available water and nutrients.
Can be determined by the feel method, the sieve method or the sedimentation method.
Once the proportions of the particles are determined a soil triangle can be used to give a description for the soil texture
Soil Triangle
Go along the side for the particle type to correct number
Draw line along the lines
For clay, parallel to sand. For silt, parallel to clay. For sand, parallel to silt
Read the soil texture from the section which the 3 lines meet
Soil Structure
Soil Structure
Arrangement of particles in a soil
Soil particles come together to form aggregates/floccules
Between the particles in aggregates are micropores
Between the aggregates are macropores
Cementation is the binding of soil particles in aggregates
Directly effecting movement of water and air
Moisture, air and temperature affect the organisms in the soil e.g plant roots and earthworms
Affects soil temperature
Effects, yield, pollution and fertilisers
Compaction
Squashing together of soil aggregates
Reduces macropores
Caused by animals and livestock on wet land
Reduces amount of air in a soil and restricts the movements of water through the soil leading to waterlogging
Can be prevented by avoiding using machinery and allowing livestock on wet land or by lightening the load. Can be improved by ploughing or subsoiling
Soil Air
Roots need to be able to respire and so need oxygen that they get from the soil air that exists in the pores between the particles. The energy from respiration in roots is used to absorb pores by active transport
When waterlogging occurs there is no air and so no oxygen present in the soil, roots cannot respire and so roots cannot absorb nutrients leading to deficiencies
Air warms up faster then water and so soils with large pore spaces (better drainage) warm up quickly in the spring
Soil Water
Needed for germination of seeds, photosynthesis and to keep plants turgid. 3 Types of soil water
Gravitational Water
Moves down through the soil with gravity temporarily available to plants before draining
Capillary Water
Moves up through the soil by capillaries. Water held in smaller pores is unavailable but most capillary water held in larger pores is available to plants.
Hygroscopic Water
Water absorbed onto soil particles as a thin layer. This water is unavailable to plants
Measurement of Water
Field Capacity
Volume of water in the soil after the gravitational water has rained
Permanent Wilting Point
Minimum amount of water in a soil that is required to prevent a plant from wilting. All available capillary water has been removed from soil. If soil water decreases further, the plant will wilt
Available Water Capacity
Water that is available for uptake by plants.
Available water capacity= Field capacity-Permanent Wilting Point
Soil Colour
Depends on minerals and organic matter present in the soil.
Dark colour indicates a soil that is rich in organic matter
Darker soils warm up faster than lighter soils