Soil - definition
Thin, uppermost layer of the earth
Uses of soil
Grows plants as food source, building, farming, pottery, antibiotics
Natural resource - definition
Essential natural resource
5 components of soil
Mineral particles, water, air, humus, organic matter
% of mineral particles in soil
45%
% of water in soil
25%
% of air in soil
25%
% humus in soil
4%
% organic matter in soil
1%
Function of mineral particles in soil
Smaller particles pack closely and slow down flow of water. Composition affects permeability
Types of mineral particles
sand (largest), silt, clay (smallest)
Mineral particles - definition
Broken down rocks
Permeability - definition
Ability of water to flow through
Function of water in soil
Binds soil together.
Dissolves minerals and nutrients in soil so plants soak them up in liquid form through roots
Function of air in soil
Found in pores (spaces) between soil particles.
Provides oxygen and nitrogen for plants, oxygen for organisms
Organic matter - definition
Anything living found in the soil, e.g. earthworms, micro-organisms (bacteria)
Plant litter - definition
Leaves and twigs
How is humus made
Plant litter decays in soil. Also formed by dead animals.
Humus - definition
Dark, gel-like material that increases soil fertility
Function of humus in soil
Fertilizes soil. Darker the soil, more humus it has and more fertile it is
Functions of worms in soil
Worms move through to help air and water circulate.
Aid in formation of humus by eating plant litter and dead animals and excreting it, fertilizing soil
How does climate impact soil formation
Provides water through precipitation
Provides frost, water, weather to erode rock that forms mineral particles
Influences vegetation and living organisms. Vegetation leaves plant litter, organisms change to humus
How does human activity affect soil formation
Fertilizer improves soil, e.g. compost
Overuse damages soil, e.g. monoculture (cultivation of single crop in given area)
How does time affect soil formation
Takes long time to form (sometimes hundreds of year per cm depth)
Soil profile - definition
Vertical section of soil from surface downwards
Horizon - definition
Soil’s layers
Characteristics of A horizon (topsoil)
Closest to surface
Dark in colour and fertile because most humus and plant litter
Characteristics of B horizon (subsoil)
Found below topsoil
Lighter in colour because less humus
More stones then top soil because closer to bedrock
Characteristics of C horizon (bedrock)
Mixture of solid rock at base and smaller pieces at top
Impacts of soil formation
Leaching, breakdown of plant litter
Why is leaching bad for soil
Deprives plants of important nutrients and minerals when washed out of reach of roots in B horizon
Creates hardpan when iron oxide minerals washes from top soil particles. Collects at bottom of topsoil just above subsoil. Causes top soil to become flooded and waterlogged
Hard pan - definition
Thin crusty layer that is impermeable
How does breakdown of plant litter impact soil formation
Plant litter broken down by insects and microorganisms to humus
Oxygen also needed to keep organisms alive
Humification - definition
The process of plant litter changing into humus
Irish soil types
Brown, podzol, gley, peaty
Formation of brown soil
Most common soil type in Ireland
Brown in colour because humus
Found in areas with not a lot of rainfall
Found in areas of deciduous forest because of plant litter
Good for farming
Formation of podzol soil
Found in upland areas with more rainfall
Grey in colour due to hardpan caused by leaching
Used for forestry as not great for farming (coniferous trees)
Not fertile because no plant litter from coniferous trees