Download Importance of Soil

The Importance
of Soil
How Soils Have Shaped Human History
• Why do you find so many Indian
artifacts (arrowheads and pottery) near
creeks, streams and rivers?
• Where are the most productive soils
found?
• The Nile Delta
• The Yellow River
• Mississippi River Floodplains
Upper Mississippi River Watershed
People settle where the good soils are!
Terraced Agriculture Production in China along Yellow River
Around 300 million people are supported by the Ganges Delta,
and approximately 400 million people live in the Ganges River
Basin…good soils support agriculture, which feed the masses
The Fertile Crescent (used to be super-fertile!)
• Flooding of Tigris and Euphrates fertilized soil
• Irrigation, drainage produced abundant crop yields
• Competition and warfare between city states (including Babylon)
• Over-salinization reduced wheat productivity in south by 2,000
B.C. - political power shifted north
• Eventual large scale ecological
destruction
• Forests cleared for fuel, ship
building
• Fields and pastures worked until
barren
Exploitation of soil resources led
to collapse of civilization!! This
area is STILL fighting over
resources
Global Soil Issues: The following slides
highlight major regional soil issues/problems
Land in the Amazon is
being cleared for tropical
timber and converted for
soy production and cattle
A lot of cotton (which is an
intensive crop) is cultivated
in central and eastern
Europe.
American Dust Bowl
• 1930s--Resulted from poor soil
management, drought,
wind erosion
• Over 150,000 square miles affected
Only about 11% of land has soil capable for agricultural
production.
Soils are made up of more
than just “DIRT”.
The soil plays a very important role in the Carbon Cycle as a storage area for
carbon, gases, water, and nutrients. Carbon produced by photosynthesis is
eventually released back into the soil and atmosphere. This has a major impact
on the global climate.
Soil is our life-support
layer:
Continental crust is about 50 miles thick
Lower atmosphere is about 25 miles deep
Soil layer is very thin (only a few feet)
Atmosphere, crust, and soil all interact to sustain life on earth—providing
sufficient temperature, oxygen (gases), water, carbon, and nutrients
Nutrient sink
Nitrogen enters the soil through the atmosphere via soil organisms
that convert nitrogen into a usable form for plants. Nitrogen is carried
to other layers, consumed in plants, returned to the atmosphere as a
gas, etc. 14 other nutrients needed by plants come from soil. C, H, O
come from air and water…the rest stored in soil.
Water Holding
Soils hold water/moisture that is absorbed by plants. “For each pound of
dry matter produced by growth, plants use between 200 and 1,000lbs of
water for photosynthesis, sap flow, nutrient use, etc.”
Temperature Regulator
Most plant roots in temperate areas grow in soil temperatures above 40-50°F
Soil provides anchorage and acts as a reservoir for water,
oxygen, and nutrients
Air and Aeration
Plant roots and soil critters use O2 and give off CO2 as they respire
Waterlogged soil has less
oxygen than “well-aerated
soils”
But…soils provide us more than just stuff to grow our food on…..
Housing
Materials to make sod and
adobe homes
Waste disposal
Landfills
Biosludge solids spread
through plantation forest
Recreation
Golf courses, parks, athletic fields
Engineering
Underground utilities,
dams, roads and building
foundations
Soil Degradation
Erosion
Desertification
Salinization
Accumulation of excess
salts
Results in part from:
• applying excessive amounts of synthetic fertilizers
• improper irrigation practices
Disappearance
According to some data, about 0.5% of agricultural soil is lost every year
through construction of different infrastructural objects and urbanization
(soil sealing).
Soil Pollution
Soil pollution typically
arises from:
• Rupture of underground storage
tanks
• Application of pesticides and
herbicides, percolation of
contaminated surface water to
subsurface strata
• Leaching of wastes from landfills
• Direct discharge of industrial
wastes to the soil
The most common chemicals involved
are petroleum hydrocarbons, solvents,
pesticides, herbicides, lead and other
heavy metals
Mining
Specific problems here in WNC
Creek debris
Peeks Creek - Macon Co, NC
What to do????
Best Management Practices
Specific practices to preserve soil and
water resources while being practical and
profitable
Conservation tillage
Buffer zones
Silt Fences