Soils Intro Flashcards
What is soil
the soilic material on the Earth’s surface that results from the interaction of weathering and biological activity on the parent material/ hard rock
How is soil made?
from the interaction of weathering and biological activity on the parent material/ hard rock
Why study soil?
Helps understand wildlife activity, potential and conservation for both plants and animals
What are the 4 principles of soil
Water
CO2 sequestration (storage)
Water holding
water purification
If there is less than 50% air and water in soil what does this mean?
It is poor soil
What percentage of soil is typically humus/ organic matter?
3-5%
What % of soil is sand?
10%
What % of soil is clay
22%
What % of soil is air?
25%
What % of soil is water?
25%
What % of soil is silt?
15%
What 7 things comprise soil?
water air humus silt clay sand living organisms/ component
Name 3 components of organic matter?
- Cellulose
- Hemicellulose
- Lignin
- Protein
- Fats, waxes
Name 3 sources of organic matter for agricultural soils
- Crop residues
- Bulky organic manures
- Sewage sludge -
- Green manure
- Composted urban waste
- Rotational practice (stubble)
What are the horizontal layers of soil known as?
Horizons
What are the A, B and C horizons?
A - top soil
B - Subsoil
C - Parent soil
What is the structure of soil horizons (5)
Humus top soil subsoil parent material bedrock
Where can the O horizon be found?
above top soil in forests
what is the o horizon?
organic matter (humus)
Which is the most important nutrient in soil?
Nitrogen
Which horizon is nitrogen mainly found?
humus layer - O horizon
Name 3 ways soils can be formed
Earth movement - earthquakes etc
Changes in sea levels
Volcanic activity
Retreat of glaciers
What are the 3 types of weathering/ erosion that can cause soil formation?
Physical
Chemical
Biological
Give an example of physical, chemical and biological weathering
Physical = freeze/ thaw, wet/dry, hot/cold, abrasion
Chemical = water disolving rock - i.e: acid dissolution in limstone
Biological - tree roots cracking rocks, earthworms mixing materials, dead organic matter
What are the 5 factors of soil formation?
Organisms Time Topography (distribution/ arrangement of the area) Climate Parent material
Which is the most important factor in soil formation?
Climate
How does climate affect soil formation?
Affects rate / type of soil
vegetation distribution - therefore nutrient content
precipitation (moisture content)
Temperature - evaporation rate (and vegetation growth, nutrients etc)
What conditions lead to leaching?
When precipitation exceeds evaporation
What is leaching
the loss of water-soluble nutrients in soil
What do micro and macro organisms do?
Micro (bacteria) - help decompose plant litter
Macro (worms, beetles etc) mix litter into soil
What influences the nature of humus, vegetation, litter etc
higher plants
What are 4 benefits of roots in soil
contribute to dead organic material
bind soil particles together
redistribute and compress soil
Remove nutrients
What are macrobiota
the living organisms of a region that are large enough to be seen with the naked eye
i.e: ants, termites, earthworms, beetles, snails, wasps, milipedes
What are mesobiota?
the intermediate size of soil organisms
i.e: o Springtails, mites, pseudo-scorpions (false scorpion)
What are microbiota?
bacteria, archaea, protists, fungi, viruses, yeast, cyanobacteria (blue-green algae)
How do cyanobacteria help soil health?
Fixes nitrogen in soil
Which organism helps fix nitrogen in soil
Cyanobacteria
How does topography influence soil formation?
slopes - influence soil thickness, nutrients, erosion, run-off, movement, microclimatic conditions
How does time influence soil formation?
Soil takes time to form
More time = more nutrients, features and materials can be added to help formation
what are the 5 processes of soil formation
1) weathering
2) decomposition and humification
3) capillary action - when evaporation exceeds precipitation (reverse leaching)
4) leaching
5) Translocation
What is decomposition
the breakdown of plant dervived material into its simpler organic constituents – accomplished by enzymes, earthworms, mites and other organisms
What is humification
the breakdown of plant remains leading to the formation of different types of humus
What is the most important BIOLOGICAL PROCESS in soils?
humification
What are 3 types of humus
Mull
Moder
Mor
Where are mull, moder and mor found
Mull - deciduous woodland
Moder - intermediate
Mor - coniferous woodland or heather moorland (wet, climatic conditions)
Which type of humus is found in deciduous and coniferous woodland?
Deciduous - mull
coniferous - mor
Why is leaching bad for soil?
It removes soluble minerals
Which types of soils have more leaching?
sandy soils - because they are more porous
What is translocation?
the movement of material in solution or suspension from one horizon to another
What happens in the Eluvial horizon?
where maximum leaching (or eluviation) takes place – the horizon that loses the minerals
What is the illuvial horizon?
- Lower horizon that gains the material - maximum accumulation happens
What does white soil indicate?
quartz or salts
What does red soil indicate
Iron oxide accumulation
what does brown or black soil indicate
type and level of organic matter
What colour will poorly drained gleys be
grey / blue-grey
what does grey/ blue colour soil indicate?
Poor drainage with anaerobic conditions (no O2) - usually gleys
What causes soil colouration?
oxidation - reduction
What is the texture of loam soil?
A combination of sand, silt and clay
Put in order of size: silt, sand, clay
Clay - smallest
Silt - intermediate
Sand - biggest
Name 3 ways texture affects soil
- Soils ability to hold water
- Soils ability to hold and supply plant nutrients
- Suitability for different plant species
- Trafficability of the land, and the ability to support structures
- Macro and micro fauna that live in the soil
What are the 4 types of soil texture
Sand
Clay
Silt
Loam
