SOILS of the Earth

What is SOIL?Thin layer of material on the Earth’s surface where plants have their roots.

Made up of weathered rocks and decayed plant and animal matter.

4 LAYERS OF SOIL

1. O HORIZON•The top layer of soil•Made up of living and decomposed materials (leaves, plants, and bugs)•It is very thin and is usually pretty dark •It is called ground level

2. A HORIZON

•The layer that we call “ topsoil”•It is made up of minerals and decomposed organic matter •Very dark in color • many plants roots grow in

3. B HORIZON

•The layer that we called “subsoil” •It has clay and mineral deposits and less organic materials •Lighter in color than the layers above

4. C HORIZON

•The layer that we call “bedrock” •It is made up of slightly unbroken rock and only a little bit of organic material is found•Plant roots are not found in this layer

WHY IS SOIL

IMPORTANT

?

oProvides ecosystem services critical for life;oPerforms many functions which make it a fundamental source for life;oProvides the place where plants conduct photosynthesis;

oProvides us home on which we build our structures;oProvides the foundation which we build our civilization; andoServes as the basis of our nation’s agro ecosystems.

FACTORS SOIL FORMATION

Factors of Soil Formation

Parent Material Climate

Time Topography

Biological Factors

SOIL TYPES

SANDY SOIL•Large particles•Dry and gritty to touch•Less water retention•Warm and airy•Easily crumbles through the fingers•Ideal for crops like: watermelon, peanuts and peaches

CLAY SOIL•Fine particles•Smooth when dry, sticky when wet•Retains water•Rich in nutrients•Ideal for plants like: leafy vegetables, tomatoes, and peas

SILTY SOIL•Tiny particles•Slippery when wet•Extremely fertile•Retains water•Ideal for crops like: all vegetables and fruits

LOAMY SOIL

•Retains water and nutrients•Easy to work with•Ideal for crops like: tomatoes, potatoes, carrots•Fertile•Well-drained

PEAT SOIL•Dark brown in colour•Soft and spongy to touch•Contains acidic water, not fertile•Improves soil buffering, mixed in soil to improve structure•Ideal for plants like: Moss, shrubs and sedges

CHALKY SOIL•Light in colour•Lime rich soil•Poor in nutrients•Free-draining•Severely dry in summers•Ideal for plants like: honeysuckle, rosa and germanium

SOIL CHARACTERISTICS

1. Soil TextureSoil description of the relative

proportions of sand, silt and clayLarge grains and pore spaces of sandy soils mean that they drain rapidly and holds little nutrients for plants.

Clay soils are easily waterlogged, which prevents the movement of oxygen in plants.

2. Soil StructureRefers to how the soil particles are

arranged relative to each other.Soil particles tend to group

themselves into blocks called “peds.”

Peds are important for increasing stability against erosion and in maintaining porosity, improving fertility and water movement.

3. Soil ChemistryStudy of chemical characteristics of soil

The terms alkaline and acid refer to the pH (Potential Hydrogen) of your soil.

pH – measure of the relative amounts of H+ and OH- in a solution

4. Soil ColorIs the most obvious and easily determined soil characteristic.

Is primarily influenced by soil mineralogy. Many soils are due to various iron minerals.

Separation of soil into classes or groups each having similar characteristics and behavior

SOIL CLASSIFICATION

Genetic classification of soils according to the US Comprehensive Soil Classification System

SOIL TAXONOMY

The Role of Soil in Ecosystems and The Effects of Soil Erosion to Man