Soil is the uppermost layer of the earth’s surface (also called the earth’s crust) on which plants grow, or the loose materials that cover the land surfaces of the earth, and supports the growth of plants.
Components of Soil:
- Organic Matter: This includes the remains of decayed plants and animals to form humus, it is about 5% of the soil by volume, it provides nutrients for plants.
- Inorganic or Mineral Matter: This forms the bulk of the soil making up about 45%, these include materials like sand, silt, and clay. It provides nutrients and support for plants.
- Solid Air: It is about 25% of the soil by volume. It provides oxygen for respiration for soil organisms.
- Soil Water: Soil water contains mineral salts dissolved in it. It represents about 25% of the soil by volume. It helps to dissolve plant nutrient in the soil and aid germination.
- Soil Organisms: These include organisms such as termites, earthworms, and decomposers like bacteria and fungi which break down organic matter to form humus.
Types of Soil:
There are three main types of soil namely: Sandy, Clay, and Loamy soil.
Characteristics of Sandy Soil:
1. Sandy soil is loose with large pore spaces.
2. It is coarse and gritty (rough)
3. Capillarity is low.
4. Has a low water-retaining capacity.
5. It is not sticky when wet.
6. Porosity is high.
Characteristics of Clay Soil:
1. Particles are highly packed with little pore spaces.
2. Percolation is low.
3. Clay soil is fine-grained and smooth.
4. Capillarity is high.
5. It is sticky when wet and hard when dry.
6. It is poorly aerated and can hold water.
Characteristics of Loamy Soil:
1. Porosity is moderate.
2. Water retaining capacity is moderate.
3. Particles are closely and moderately packed.
4. Has a good mixture of sand and clay with a lot of humus.
5. Has moderate pore spaces.
6. Best for agricultural purposes, because it holds plenty of moisture, but also drains well so that sufficient air can reach the roots.
Uses/Importance of Soil:
1. Source of all minerals used by man.
2. Agricultural purposes as food and cash crops are grown on it.
3. Building construction as materials for making blocks and bricks are derived from it.
4. Anchorage for plants.
5. Reservoir for water and air.
6. Grazing of animals.
7. Making pottery (pots, marble), etc.
8. Habitats for organisms.