soil - properties and processes Flashcards
why is soil important?
grows crops/food
stores carbon - helps mitigate environmental pollution
building foundation
ecosystems - supports life/ nutrients
influences quality of surface and groundwater resources
where does soil come from?
from pure black rock from fresh volcanic fields
this weathers over of 100s of years
creates rusty brown rock with few plants/lichen
100 yrs later
broken down into soil creating fully functioning ecosystem colonised by life.
name the 9 elements which make up earths crust?
iron silicon calcium sodium aluminium hydrogen oxygen magnesium potassium
how much pedigrams of carbon in soil?
1.5 to 2.5 thousand
400-600 for vegetation
name the 4 soluble cations?
sodium
magnesium
potassium
calcium
define soluble
easily leaches/dissolved in water
define cation
positively charged ion
name the 5 less soluble cations?
oxygen hydirgen iron aluminimum silicon
what does it mean by less soluble cations
they remain in soil as clays or oxyhydroxides
define soil
natural body with solids, liquids and gases
distinguished horizons or layers
losses/additions/ transfers of energy
supports rooted plants
what is the composition by volume of a topsoil
air - 25%
water - 25%
solid - organic matter 5% (humus 80% - roots 10% - organisms 10%)
mineral particles 45% (Clays/sands)
how is soil an open system
inputs
outputs
transfers
transformations
inputs into soil
rain
solar energy
manure
harvesting
outputs of soil
erosion - wind and water
human activity
transfers in soil
water transfer to streams
ground water percolation
veg uptake of water and nutrients
mechanical mixing
transformations in soil
clay mineral formation
mineral weathering
what makes up the topsoil
o horizon
a horizon
e horizon
what makes up subsoil
b horizon
what makes up the transition region?
c horizon
whats at the bottom of the soil profile ?
unweathered parent material
O horizon
loose
particially decayed organic matter
thin
A horizon
mineral matter mixed with humus
animals help mix it
acididic - leaching can occur
thick
E horizon
zone of eluviation and leaching
white
B horizon
accumulation of clay
transported and leaching from above
rich in chemical weathering products
C horizon
partially altered parents material
can be glacial till
name 5 main uk soils
brown earth podzol lithomorphic gley peat
Define brown earth
humus well mixed
leaching lead to slight acidifcation
nutrient rich - goof for farming
base rich parent material
define podzol
mor humus
poorly mixed
strongly acidic
leaching iron and aluminimum
found in conifer areas as pine needles acidic
base deficient parent material eg granite
define lithomorphic soil
limestone dissolves as it weathers leaving no soil minerals
not great for farming
alkaline from calcide
grasslands/beech lowlands
freely draining
define gley soils
peat accumulation
poorly drained
oraganic rich at top
oxidation and reduction reactions craete orange soil
acididic to neutral
boggy
define peat soils
organic matter accumulation in waterlogged conditions forms peat - paludification
poor drainge
boggy
acidicic - neutral
describe soil distribution in uk
north - gley
wales/cornwall - podzol
south - brown with lithomorphic bits
peats least disttibuted in uplands
what controls soils distribution in the uk
rainfall more in west than east
glacial till location - clay rich has poor drianage
bedrock type - underlying rock - south its chalk and clay
altitude - peat high up
what 2 things control soil thickness
supply
kinetic
what is supply
rate at which soil forming material are delivered to surface
what is kinetics
rate at which bio/chem/phys processes act on soil
define supply limited soil
soil growth limited by delivery of appropriate earth material
akin to weather limited sloped
define kinetic limited soil
soil growth limited by speed at which soil forming processes progress
akin to transport limited slopes
what soil does supply limited contol?
gley
peat
lithomorphic
what soil does kinetic limited control
brown earth
podzol
