HomePrimary 4Agricultural Science Primary 4Causes of soil infertility

Causes of soil infertility

 

 

AGRICULTURAL SCIENCE THIRD TERM E NOTES FOR BASIC FOUR

3rd Term Agricultural Science

Primary 4

 

Subject : AGRICULTURAL SCIENCE

 

Topic : Causes of soil loss of Nutrients

 

Class : BASIC FOUR / PRIMARY 4 / GRADE 4

 

 

 TERM : FIRST  TERM  

 

 

WEEK : WEEK 6

 

 

LEARNING MATERIALS

  • Whiteboard/Chalkboard
  • Explanatory posters/pictures
  • Explanatory videos

 

Instructional Materials :

  • Lagos State Scheme of Work.
  • Online Materials.
  • Textbooks
  • Workbooks
  • Different types of soil

 

 

Previous Knowledge :

The pupils have been taught

THE FORMATION OF THE SOIL

in their previous lesson

 

PERFORMANCE OBJECTIVES

At the end of the lesson , pupils should be able to

 

1. say the meaning of soil fertility

2. Explain what actions or behavior of Farmers that can make soil to lose its nutrients

 

 

Content :

Causes of loss of soil fertility

Soil is said to be fertile when all the nutrients necessary for plant growth and development are present in it. Soil can lose its fertility in five main ways:

In some places, big forests and vast grasslands are set on fire to burn. Some of these areas are good farmlands. When this is done, dead and decaying leaves, grasses and living soil organisms are burnt. Dead leaves, grasses and soil organisms add fertility to the soil. Soil, therefore, loses its fertility when they are burnt.

Leaching

This is the downward movement of nutrients from the top soil to the underground layers of the soil. Some nutrients dissolve in water for plants to absorb as food. When rain falls, some water collects in low-lying areas of the farm and stays there for some time. As this water sinks into the soil, it carries with it dissolved soil nutrients. These nutrients can no longer be available to the plants growing On the surface of the soil. The nutrients are lost or leached away.

Erosion

This is the gradual wearing away of the top soil by water or wind. When rain falls, water flows on the surface of the soil. The water carries the top soil along with it. The top soil contains nutrients dissolved in water. These nutrients are carried away by the flowing water and are no longer available for plants to use.

Wind blows and carries some soil particles from one place to another. This soil contains some nutrients which are also carried away by the wind.

Crop removal

The crops that farmers plant in their farms absorb nutrients from the soil for their growth and development. These nutrients, once taken up or absorbed, are no longer in the soil. Another crop planted in the same soil the following year may not have sufficient nutrients for its own growth and development.

Clean clearing

Leaves on forest trees drop on the soil. These leaves die and decay, and add nutrients to the soil. When these trees are removed and the forest under growths cut, the soil loses its regular supply of nutrients from the forest.

 

 

 

Presentation

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

 

 

Evaluation:-

 

Answer the following questions

  1. The process whereby rocks are broken down to form soil is known as ______ (a) Transformation (b) Weathering (c) Osmosis
  2. The physical properties of Soil consists of ______ (a) solid, liquid and gas (b) solid and liquid (c) gas only
  3. The solid components of soil are also known as soil ______ (a) physical (b) particles (c) nutrients
  4. Soil pores are used by soil to ______ (a) retain water and air (b) produce pores (c) movements
  5. What percentage of soil is made up of air (a) 45 (b) 5 (c) 25
  6. What percentage of soil is made up of mineral matter? (a) 45 (b) 5 (c) 25
  7. Which soil type is having the highest porosity (a) clay (b) sandy (c) clay
  8. The parent materials of soil are ______ (a) Men (b) Rocks (c) Mineral resources
  9. The processes of breaking down rocks are physical, chemical and ______ (a) biological (b) systematic (c) Manually
  10.   ______ makes the rock to expand, crack and break down into small pieces. (a) Rainfall (b) High temperature (c) Tension

 

Conclusion :

 

The teacher summarize the lesson. He or she gives out a board summary of the topic as note . He or she goes round to mark and does the necessary corrections

 

 

 

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