2. Content
What is soil?
Soil formation
Weathering
Soil development
Factors influence soil
formation
Soil Profile
Soil composition
Physical properties of
soil
Soil texture
Types of soil and
comparison
Chemical properties
Humus
Soil Water
Soil Air
Soil reaction
Soil Organism
Problems regarding soil
Conservation of soil
3. What is soil?
It is originated from Latin word ‘solum’.
It is basic natural resources.
Soil is a mixture of organic matter,
minerals, gases, liquids, and organisms that together
support life.
The study of soil is called pedology or edaphology.
5. Soil formation
It can be divided into two major stages-
1. Weathering
2. Soil development
6. 1. Weathering
This process performed by three methods-
Physical Weathering
Chemical Weathering
Biological Weathering
7. 2. Soil development
It is also called Pedogenesis or Soil Maturation.
Organisms such as bacteria, fungi, algae, lichens etc.,
help in this process.
A mixture of Organic and Inorganic substances is
formed by humus. This is called Soil.
9. Soil profile
A vertical section of soil in which many horizons of soil
are seen is called Soil Profile.
Horizon-A (Top Soil)
o O1 Horizon
o O2 Horizon
o A1 Horizon
o A2 Horizon
Horizon-B (Sub-Soil)
Horizon-C (Parent Rock)
Horizon-D (Bed Rock)
12. Physical properties of soil
1. Soil Colour
It can be different colour in different places but soil colour does
not affect their working system.
2. Porosity
Empty spaces are present among soil particles those have soil
water and soil air.
3. Soil Permeability
The power of soil to allow water to pass through it.
13. 4.Soil texture
Particle size-
Gravel = >5.000mm in diameter.
Fine Gravel = 2.000-5.000mm
Coarse sand = 0.200-2.000mm
Fine sand = 0.020-0.200mm
Silt = 0.002-0.020mm
Clay = <0.002mm
16. Chemical properties
Mineral matter or inorganic matter
o Macronutrients
o Micronutrients
Organic matter or humus
17. Humus
It is dark organic matter that forms in
soil when dead plants and animal matter
decays.
Types of Humus-
18. Soil water
It is the most significant factor because the absorption of
minerals and organic matter through roots takes place by
water only.
Soil water balance
20. Soil air
The air present in soil.
Following activities of plant performed by soil air-
Water absorption
Growth of roots
Formation of new root hairs
Respiration by roots
Seed germination
21. Soil reaction
The soil may be neutral, acidic or basic.
pH of soil varies from 3-9.
The value of pH the effects the concentration and
availability of other minerals.
The plant growth is good between 6 to 7.5 pH.
22. Soil organisms
Soil organisms are commonly
divided into five arbitrary
groups according to size, the
smallest of which are
the protists—including bacteria,
actinomycetes, and algae.
23. Problems of soil
Soil erosion
Desertification
Salinisation and Alkalisation
Impact of Intensive
Agriculture
Urbanization and
Contamination
24. Conservation of soil
There are three main methods-
1.Agronomical measures
• Contour farming
• Strip cropping
• Cover cropping
• Crop rotation