soil & soil functions

soil facts
Soil is the most biologically diverse ecosystem on the planet. More diverse than the rainforest and ocean.
In one cup of healthy soil, there are about 200 billion bacteria, 100,00 meters² of fungi, 20 million protozoa, 100,000 nematodes, 50,000 arthropods, and possibly 1 earth worm.
soil defined
Soil is a 3 Dimensional body comprised of mineral and organic solids, gases, liquids, and living organisms, formed from the weathering of mineral and organic parent material over the progression of time.
OR: Soil is a living, dynamic matrix comprised of mineral particles, air, water, organic matter and a complex community of living organisms.
Dirt is dust and dead particles.
Soil ≠ Dirt
soil functions
Medium for plant growth
Provides essential nutrients and acts as an anchor for roots. Facility for seeds, water, and oxygen. Temperature Regulation
Regulates and purifies water
Recycles wastes and nutrients
Transforms toxins through "nutrient cycling"
Modifies the atmosphere
Releases and stores nitrous oxide, carbon dioxide, methane and oxygen. (greenhouse gases)
Habitat for organisms
As mentioned earlier, billions of organisms reside in the soil.
Engineering medium
We live on the soil; buildings, homes, universities, streets, highways.. etc.
soil components
Minerals (solids) about 45%
sand, silt, clay particles
Water about 25%
Air about 25%
Organic matter about 5%
soil horizons
O Horizon:
Organic layer, common in temperate forests, rare in deserts and semi-arid grasslands.
Only organic matter
A Horizon:
AKA Top Soil (crushed oreo cookies)
Mineral organic layer; particles can be darkened due to organic matter
E Horizon:
Zone of eluviation (exit)
Heavily leached, lighter in color due to leaching
B Horizon:
Zone of iluviation (into)
Red in color due to accumulation of clays, oxides, and silicates
C Horizon:
Least weathered and least impacted by soil forming factors