Chapter 1The Importance

of Soil

How Soils Have Shaped Human History

• The Nile Delta

• The Yellow River

• Mississippi River Floodplains

• Why do you find so many Indian artifacts (arrowheads and pottery) near creeks, streams and rivers?

• Where are the most productive soils found?

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 thickLower atmosphere is about 25 miles deepSoil 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 sinkNitrogen 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 HoldingSoils 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 AerationPlant 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 andadobe homes

Waste disposal

Biosludge solids spread through plantation forest

Landfills

Recreation

Golf courses, parks, athletic fields

Engineering

Underground utilities, dams, roads and building foundations

Soil Degradation

Erosion

Desertification

SalinizationAccumulation 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

Buffer zones

Silt Fences

Conservation tillage