Soil: A Renewable Resource

Soil: A Renewable Resource PA Standards

3.1.12.C: Unifying Themes 3.7.12.B: Technological Devices 4.6.12.C: Ecosystems and their

Interactions

“Land, then, is not merely soil; it is a fountain of energy flowing through a circuit of soils, plants, and animals.”- Aldo Leopold, A Sand County Almanac, 1949

Evaluate change in natural systems.

Analyze how natural changes affect the balance within an ecosystem.

Assess and apply recurring patterns in natural systems.

Evaluate appropriate instruments and apparatus to accurately measure materials and processes.

Key Questions

What are soils and how are they formed? What happens to matter in an ecosystem? What are the soil horizons and how do

they indicate the principal soil type? What are the different properties of soil?

What are soils and how are they formed?

Importance of Soil What is Soil?

Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms (microscopic decomposers)

Why is it important? Base of life on land. Provides most of the nutrients needed for plant growth

and also helps purify percolating water and store water. Helps decompose and recycle biodegradable wastes. Stores carbon as carbon compounds.

What happens to matter in an ecosystem?

Soil as a Resource

How does it form? Bedrock broken down into rock fragments and

particles by physical, chemical, and biological processes called weathering.

Lichens add nutrients and when they die add organic matter

Renewable resourceVery slowly – 1 cm (0.4 inch) of soil can take

from 15 to hundreds of years to formMature soils, or soils that have developed over a

long time, are arranged in a series of horizontal layers called soil horizons.

What are the soil horizons and how do they indicate the principal soil type?

Soil Horizons

Soil Profiles of the Principal Terrestrial Soil Types

Layers in Mature Soils Infiltration

The downward movement of water through soil.

LeachingDissolving of minerals and organic matter in

upper layers carrying them to lower layers. The soil type determines the degree of

infiltration and leaching.

What are the different properties of soil?

Some Soil Properties

Soils vary in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them.

Porosity: the amount of empty pore space in the soil

Permeability: the ability of a soil sample to transmit fluid

Sand has high porosity and high permeability

© Brooks/Cole Publishing Company / ITP

Fig. 5–17

Soil texture is determined by the particular mix of clay, silt, & sand.

Who Am I?

5% clay, 15% silt, 80% sand

Loamy sand

40% silt, 35% clay, 25% sand

Clay loam

9% sand, 85% silt, 6% clay

Silt

16% sand, 55% silt, 29% clay

Silty clay loam

Try these…

% Sand % Silt % Clay Texture Classification

30 20 50

50 20 30

40 40 20

10 60 30

30 40 30

60 30 10

10 45 45

How did you do?

% Sand % Silt % Clay Texture Classification

30 20 50 Clay

50 20 30 Sandy Clay Loam

40 40 20 Loam

10 60 30 Silty Clay Loam

30 40 30 Clay Loam

60 30 10 Sandy Loam

10 45 45 Silty Clay

Activity

Soil Texture Analysis ActivityTexture by FeelTexture by Sedimentation

Soil Texture Triangle

Review Key Questions

What are soils and how are they formed? What happens to matter in an ecosystem? What are the soil horizons and how do

they indicate the principal soil type? What are the different properties of soil?

Thought Problems What type of soil would produce high crop yields? What

type of terrestrial types (biomes) are these found?

Why is the humus beneficial?

What layers of soil are the roots of most plants and the majority of a soil’s organic matter concentrated?

What color soil would be good for growing crops?

Which layers have the most amount of inorganic matter?

Is a more or less porous soil better for plant growth?

Thought Problems - Answers What type of soil would produce high crop yields? What type of terrestrial types

(biomes) are these found? Fertile soil with thick topsoil layer with lots of humus. They are found in grasslands or

deciduous forests. Why is the humus beneficial?

It helps the topsoil hold water and nutrients taken up by plant roots. What layers of soil are the roots of most plants and the majority of a soil’s organic

matter concentrated? The top two layers.

What color soil would be good for growing crops? Dark brown or black – rich in nitrogen and organic matter. Gray, bright yellow, and red

topsoil's have low organic matter and nitrogen. Which layers have the most amount of inorganic matter?

The B horizon (subsoil) and C horizon (parent material). Is a more or less porous soil better for plant growth?

More porous – it contains oxygen, necessary for cellular respiration, and nitrogen gas.