1. Soil as a Natural Resource

Learning Outcome

• At the end of this section the students will be able to define soil and identify the major components of a soil

Natural Resources

• Living – Animals and Plants (Renewable, Non Renewable)

• Non Living – – Perpetual : Solar Energy, Wind, Tide, Flowing

Water– Renewable : Fresh air, Soil, Fresh Water– Non Renewable : Fossil Fuels, Metallic

Minerals, Non-metallic minerals

Soils as a Natural Resource

“The thin layer of soil covering the Earth’s surface represents the

difference between survival and extinction of most terrestrial life”

What is a soil?

Soil

• Medium for plant growth – food production

• Without soil, terrestrial ecosystems would not exist

• Forms relatively a thin mantle over the earth

• Early civilizations – Nile, Tigris, Euphrates, Indus, Yangtze, Hwang Ho – fertile soils

• Civilizations declined due to decline and misuse of land and soil

Soils

• Crucial to land use planning

• Waste disposal

• Evaluation of natural hazards– Flooding – Landslides– Earthquakes

• Evaluation building construction

• A renewable resource

• Man’s actions made it very fragile – highly susceptible to damage and misuse

• Takes hundreds to thousands of years to develop few centimeters of soil

• If not managed properly, it will become a non-renewable resource

Soils defined

• Natural body that occurs on the land surface, occupies space, and is characterized by one or both of the following:– Horizons or layers– Upper limit is air or shallow water (less than

2.5 m) and Lower limit is either bedrock or the limit of biological activity (usually set at 2 m)

Soil Definition

• Unconsolidated mineral matter on the surface of the earth that has been subjected to and influenced by genetic and environmental factors of: parent material, climate (moisture and temperature), macro and micro organisms, and topography, all acting over a period of time and producing a product soil that differs from the material from which it is derived in many physical chemical and biological properties and characteristics (SSSA)

Soil Scientist:Solid earth material that can support rooted plant life

Non Soil Areas

• Beaches• Active pits • Urban Lands• Deep water habitats• Bed rock

Areas that do not support plant growth are not considered soil but are mapped as miscellaneous areas in soil survey reports.

Soil Components

Soils consist of four major components: 

(1) mineral (or inorganic),

(2) organic,

(3) water, and

(4) air.

Relative proportions vary with soil type and climatic conditions.