Agricultural Science JSS 2, Week: 1
Topic: Soil, Its Physical Composition and Properties
Soil can be defined as the uppermost layer of the earth where agricultural activities are carried out. The top layer of the earth’s surface, consisting of rock and mineral particles mixed with organic matter.
Soil Components
The soil is made up of the following components
- Mineral matter
- Organic matter
- Soil water
- Soil air
- Living organism
A. Mineral matter
This accounts for the majority of the solid in most soil. It consists of stones, gravel, sand, silt and clay. It is about 45% of the total volume of the soil.
B.Organic Matter
Soil consists of rock particles and certain amount of organic material called humus. Humus refers to the dead decay of the leaves, roots of plants, residue of crops and animal dung. It is about 5% of the total volume of the soil.
C.Soil water
Soil water refers to the water in the soil which is obtained from rainfall, irrigation and underground water. There are four forms of soil water. These are gravitational water, capillary water, hygroscopic water and field capacity. Soil water represents about 25% of the total volume of the soil.
D.Soil Air
This refers to the gases present in the soil e.g. nitrogen, ammonia etc. The percentage of air is about 25% of the total volume of the soil.
