Soil is the end product of:
Soil functions:
1) Carbon sequestration
2) Provision of food, fibre and fuel
3) Water purification and soil contaminant reduction
4) Climate regulation
5) Nutrient cycling
6) Cultural heritage
7) Flood regulation & erosion
8) Construction material
9) Source of pharmaceutical resources
10) Human infrastructure
11) Habitat for animals
Soil formation:
The formation of soil:
1000 years or more
Soil = the weathering of
rocks and minerals+
moss + organic matter
Soil profile
Organic
Surface (top soil with living creatures and minerals)
Subsoil (zone of leaching)
Substratum (partially weathered)
Bedrock (unweathered, no soil)
Soil types
Sandy (gritty wont hold together) - leaches nutrients +fast drainage warms quickly
Clay (heavy compact sticky) - prone to waterlogging + retains water and nutritious soil
Silty (found near rivers, wont hold together) - medium drainage capacity + fertile good water retention
Chalky (fine stony fine particles) - low in nutrients + alkaline no need to add lime
Peat (dark rich in organic matter acidic) - high acidity low decomposition rate + good addition to other soils (11% in Scotland)
Loam (mix of all types of soil) best soil ever
Soil is a living thing
1/4 of biodiversity held in the soil
1 tea spoon of soil same as people on earth
Soil Food Web:
interaction of soil
biodiversity, plants
animals from the
ecosystem =
complex web of
ecological activity
First level- photosyntheses -plant and organic matter
Second trophic level - decomposers
bacteria, fungi and nematodes
Third trophic level - predators
nematodes, protozoa
Fourth and Firth trophic level
predators (fifth level animals like birds)
Bacteria
rhizobia contains nitrogenase enzyme that breaks down the nitrogen, forming Ammonia
rhizobia requires a host
Chemistry vs biology
industrial agriculture vs sustainable agriculture
chemical fertilizers - agricultural steroids
1/32th of the soil in the
planet can be used to
grow food.
Losing soil
Factors:
growing population,
climate change
poor management
erosion
deforestation
exploitation
chemical - water pollution
overgrazind
Soil is the foundation for
food production
Causes for loss of soil
desertification - drier due to
human activity
salination - due to irrigation
acidification
sealing - paving
compaction
loss of organic matter
loss of living organism
loss of nutrients
carbon release
/ climate change
Soil stores Nitrogen
Phosphorus and
other essential nutrients
• Half of the topsoil on the planet
has been lost in the last 150 years.
• 24 billion tonnes or 12 million
hectares of topsoil are lost every year.
• We may only have 60 years of
harvests left in the soil?
Land use conversion and
drainage of organic soils for cultivation are responsible for 10% greenhouse emissions
Greenhouse emissions from agriculture, forestry, fisheries 50% higher over the past 50 yrs
“We abuse land because we regard it as a commodity belonging to us. When we see
land as a community to which we belong, we may begin to use it with love and respect.”
LEOPOLD, A. 1949. A Sand County almanac. Oxford: Oxford University Press.
Consequences of soil degradation:
water scarcity, low nutrients, food poverty,
climate change, migration, reduction of ecosystem services
Sustainable soil management
zero till, soil governance, appropriate waste disposal, land planning, waste water treatment, crop rotation, increase organic matter
Howard 1940 saw direct link between healthy soil and health of people. You are what you eat eats!
Over the last 80 yrs level of nutrients
in most foods have fallen compared
to 1940s. meat x 2, fruit 3 x,
vegetables 5 x - this reflects the
nutrient depletion from animals and plants
study by Dr Thomas
