SUBJECT: AGRICULTURAL SCIENCE
DEFINITION AND TYPES OF SOIL
JSS 2 (BASIC 8)
Instructional Materials :
Previous Knowledge :
Behavioural Objectives : At the end of the lesson, the pupils should be able to mention types and uses of soil
- Online Resource Materials
- Various Textbooks
- Lagos State Upper Primary Scheme of Work
TOPIC: DEFINITION AND TYPES OF SOIL
(i) Definition of soil.
(ii).Composition of soil.
(iii)Type of soil
The soil is the environment in which the roots of crops are found. It is formed from breaking down of rocks into smaller pieces.
SUB TOPIC 1: DEFINITION OF SOIL
Soil can be defined as the topmost layer of the earth`s crust on which plants grow.
It can also be defined as the natural material formed from weathered minerals and organic matter, which covers the upper layer of the earth.
Soil is divided into three layers namely,
- Top soil: This is where most plant roots are found. It is darker brown than the soil beneath it .It contains many parts of dead plants and animals, which later form the humus.
- Subsoil: This is the soil below the topsoil. It is relatively infertile.
- Parent rock: This is the region below the subsoil.
- Soil is form from ……….
- Define the term soil
- Mention the three layers the soil is made up of
Sub topic 2: COMPOSITION OF SOIL.
The soil is made up of the following: air , water, organic matter, inorganic matter and living organisms. The first four are referred to as the physical component of the soil while the last one is the biological component of the soil.(This percentages vary with different types of soil found in different places.
1.SOIL AIR: Air is present in the pore spaces in the soil which are not occupied by water. This provides O2 for the respiration of living organisms in the soil and help seeds to germinate. Soil air is higher in moisture and CO2 but lower inO2 than the atmospheric air. It is about 25% by volume in the soil.
2.SOIL WATER :This is the water present in the soil. The soil pore spaces that are not filled with air are filled with water. It is about 25% by volume in the soil. Water is important in the soil for the following reasons:
- It dissolves plants nutrients
- It regulates soil temperature
- It is needed for photosynthesis.
- It is an agent of rock weathering.
- It is needed for seeds to germinate.
- It help plants to maintain turgidity.
3. SOIL ORGANIC MATTER (HUMUS): This consists the mixture of plants and animals residues in their various stages of decomposition. It is about 10% by volume in the soil.
4. MINERAL MATTER(soil particles):These are the solid parts of the soil which are derived from weathered rocks. They supply the mineral elements plants use as food. It is about 40% by volume in the soil.
5. SOIL LIVING ORGANISMS: These include all living things living in the soil. These include small mammals like, rats, insects and micro organisms such as nematodes, protozoa, fungi etc .Some of them are beneficial while some are dangerous to crops.
- List the five things the soil is made up of
- Which of these is referred to as the biological component?
- Give diagrammatical representation of the component.
SUBTOPIC 3:TYPE OF SOIL
The main types of soil are
CHARACTERISTICS OF SANDY SOIL.
- it is well drained and well aerated.
- It has low water holding capacity.
- It is easily heat up during the day and easily cool down at night.
Iv. It is easy to work on.
v. It is poor in plant nutrients, thus poor for crop production.
vi. It is easily washed away by erosion.
vii. Its particles do not stick together, hence it can not be moulded.
viii. It is coarse, rough and gritty when touch.
NOTE: Sandy soil can be improved by adding humus.
CHARACTERISTICS OF CLAYEY SOIL.
1. It has high water holding capacity.
2. It particles are fine and smooth to touch.
3. It is sticky when wet and could be moulded.
4. It is poorly aerated.
5. It is heavy to work on but rich in plant nutrients.
6. It is usually very cold and does not become hot easily.
NOTE: A soil is said to be clayey when clay fraction is more than 25% in the mixture.
Clayey soil can also be improved by adding humus and by adding lime to reduce the level of acidity.
CHARACTERISTICS OF LOAMY SOIL.
1.It is well drained and well aerated.
2. It is easy to cultivate.
3. It is fairly smooth and fairly plastic(sticky).
4. It has good air space and good drainage.
5.It is rich in plant nutrients.
NOTE: Loamy soil combines the good physical properties and good chemical properties of clay, it is therefore the best soil for crop cultivation.
CHARACTERISTICS OF SILT.
The properties of silt are mid-way between that of sand and clay
1. They are smooth, powdery and have large surface area.
2. They have moderate temperature and are slightly sticky.
1. State three characteristics each of the following:
2. When is a soil considered to be sandy soil?
3. How can a farmer improve clay soil for crop production?
FIVE OBJECTIVES AND TWO THEORIES.
- Junior Secondary Agriculture For Nigerian Schools By Anthony Youdeowei et al
- Intensive Agricultural science For JSS 1-3 By E . U Okaro
- Prescribed Agricultural science for JSS by S.A. Omoruyi et al
The topic is presented step by step
Step 1: The class teacher revises the previous topics
Step 2. He introduces the new topic
Step 3: The class teacher allows the pupils to give their own examples and he corrects them when the needs arise
- What is soil
- How is soil formed
- Mention three types of soil
- Mention three components of soil
- Mention three layers of soil
The class teacher gives a brief note and he goes round to mark