Post on 24-Feb-2016
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Soil: Not Just ‘Dirt’
What is Soil?
Soils are a major component of the world’s ecosystems.
They form at the interface of the Earth’s atmosphere, lithosphere (rocks), biosphere (living matter) and hdyrosphere (water).
What is Soil?
Soil is what forms the outermost layer of the Earth’s surface.
Soil comprise weathered bedrock (regolith), organic matter (both dead and alive), air and water.
LIKE LIVING SKIN OF THE EARTH!
What is soil?
Soil has matter in all three states:
• organic and inorganic matter form the solid state
• soil water form the liquid state (precipitation, groundwater and seepage)
• soil atmosphere forms the gaseous state
Functions of soil
Functions of soil
Soils are important to humans in many ways:• soil is the medium for plant growth,
which most of foods for humans are grown in
• soil stores freshwater, 0.005% of world’s freshwater
• soil filters materials added to the soil, keeping quality water
Functions of soil
• soil is nature’s recycling system. Waste and dead matter are decomposed and their nutrients made available for new life.
• soil is the habitat for billions of micro-organisms, as well as other larger animals
• soil provides raw material in the forms of peat, clay, sands, gravel and minerals
Functions of soilSoils breathe!
Gases are exchanged between the soil surface and the air. Gases like oxygen and methane are absorbed, while, while gases like carbon dioxide and nitrous oxide are released. The soil provides a valuable carbon sink. The evaporation of soil moisture also affects air temperature and weather patterns.
Soil Biology
Soil is by far the most biologically diverse part of the earth.
It contains a complex food web of prey, predators and decomposers.
These organisms require the same elements we require: air, water, food and shelter.
Soil Biology
Soil Biology
One teaspoon of healthy soil may contain:
• Bacteria- 100 million to 1 billion• Fungi- up to 100 yards of fungal hyphae• Protozoa- several thousand• Nematodes- up to several hundred• Arthropods (insects,spiders,centipeds)-500-2000• Earthworms- arid soils may have none to several
Soil Horizons
Soil Horizons
O – Organic Horizon:
l - undecomposed litterf – party decomposed litterh – well decomposed humus
Soil Horizons
A – Mixed mineral-organic Horizon:
h – humusp – ploughed in field or gardeng – gleyed or waterlogged
Soil Horizons
E - Eluvial or leached Horizon:
a – strongly leached, and ash colouredb – weakly bleached, light brown
Soil Horizons
B – Illuvial or deposited
Fe – iron depositedt – clay depositedh – humus deposited
Soil Horizons
C – Bedrock or parent material
r – rocku – unconsolidated loose deposits
Soil Horizons
Formation of soil
Soil forming process consists of: Gains and losses of material to
and from the profile Movement of water between the
horizons Chemical transformation within
each horizon.
Soil is formed from rocks and decaying plants and animals.
Formation of soil
Therefore soils are open systems in a steady-state
equilibrium
Formation of soilThe principle processes include
• Weathering• Translocation• Organic changes (degradation, humification, mineralization)• Gleying (waterlogging)
Formation of soil
Formation of soil
Soil Formation
Natural processes can take 500 years to form one inch of top soil.
http://www.pearsonhotlinks.com/
Soils are vital to humans, but take a long time to develop, so should be
considered a non-renewable resource
Soil Degradation
Value of Soil
“The soil is the great connector of lives, the source and destination of all. It is the healer and restorer and resurrector, by which disease passes into health, age into youth, death into life. Without proper care for it we can have no community, because without proper care for it we can have no life.”
― Wendell Berry, The Unsettling of America: Culture and Agriculture
Symphony of Soilhttps://www.youtube.com/watch?v=K5QYZ-LRXW4
Dirt: The Moviehttps://www.youtube.com/watch?v=lvrww8iMl-A
Movies
Painting with soil
A little research……..
• What is pedology?• What is compost?• How to make compost? Is it possible to make compost at home or at school?