Soil is composed of minerals, organic matter, living organisms, air, and water. It has a profile of distinct horizontal layers called horizons, including the topsoil-rich A horizon, the nutrient-rich B horizon below, and the weathered C horizon atop bedrock. Different soil types form in various climates - for example, podzol soils occur in rainy forests while chernozem soils are common in grasslands. Soil can gradually shift down slopes through creep, and its quality can deteriorate over time through depletion of nutrients or erosion by water, wind, or human activities.

1. CHAPTER 6

2. Concept Notes
•SOIL
Loose covering of broken rocky material and decaying
organic matter overlying the bedrock of the Earth’s
surface.
Comprised of minerals, organic matter called Humus.
Humus are derived from decomposed plants and
organisms, living organisms, air, and water.
Pedology – study of soil

3. • SOIL PROFILE
A vertical cross-section from ground-level to the bedrock on which
the soils sits.
The profile is divided into layers called Horizons
A Horizon (TOPSOIL) – is the uppermost layer, consisting primarily of
humus and living organisms and some mineral materials. It is rich in
humus due to decomposition of a thick of dead grass of the surface.

4. B Horizon (SUBSOIL) – is the
layer where most of the
nutrients accumulate and is
enriched in clay minerals.
C Horizon – is the layer of
weathered parent material at
the base of the soil.

5. • TYPES OF SOIL PROFILE
Podzol – is common in coniferous forest regions where precipitation
exceeds evaporation.
Chernozem – are found in grassland regions, where evaporation exceeds
precipitation.
The organic content of soil is widely variable, ranging from zero in some
desert soils to almost 100% in peats.
soils influence the type of agriculture employed in a particular region –
light well-drained soils favorable farming, whereas heavy clay soils give
rise to lush pasture land.

6. • SOIL CREEP
 Gradual movement of soil down a slope in response to gravity.
 Evidence formation of soil creep, Terracettes (step like ridges along the
hillside), leaning wall, telegraph poles, and trees that grow in a curve to
counteract progressive leaning.

7. •
• SOIL DEPLETION
Destroy in soil quality over time.
Causes include:
loss of nutrients caused by over farming
erosion by wind
chemical imbalances caused by acid rain
•

8. •
• SOIL EROSION
• Soil erosion is the process by which the top layer of soil is removed or
displaced by natural forces such as water, wind, or human activities.
• It can occur gradually over time or suddenly during events like heavy
rainfall or strong winds.
• Soil erosion can have detrimental effects on agriculture, the
environment, and land quality, as it can lead to the loss of fertile soil,
increased sediment in water bodies, and damage to ecosystems.
• Conservation measures, like planting cover crops and building terraces,
are often employed to prevent or mitigate soil erosion.

9. • DESERTIFICATION
 Spread of deserts by changes in climate,
or by human-aided processes.
 MARRAM GRASS – has a rolled leaf that
creates a localized environment of water
vapor concentration within the leaf, and
helps to prevent water loss.
About 30% of land worldwide is
affected by desertification (1998),
including 1 million hectares in Africa
and 14 million hectares in Asia.