SS 1 Second Term Agricultural Science Lesson Note – Soil Formation and Profile Development

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SUBJECT: AGRICULTURAL SCIENCE

DATE:

CLASS: SS1

TOPIC:  SOIL FORMATION AND PROFILE DEVELOPMENT.

CONTENT:

1. FACTORS OF SOIL FORMATION
2. PROCESS ES OF SOIL FORMATION
3. SOIL PROFILE DEVELOPMENT

 Introduction:  soil is very important factor for agricultural activity and survival of man. Soil is the loose weathered materials covering the surface of the earth, which supports life. It can also be defined as the outer most part of the earth that is formed from mixture of minerals and decaying organic matter which extends from the surface down to the limit of biological forces.

Sub topic 1:

Factors of soil formation:

The transformation of rocks into soil is referred to as soil formation. The first stage in the process of soil formation is the Weathering of Rocks which involves the breaking of rocks into smaller particles and eventually into individual minerals that the rock is composed of. Weathering of rock can either be Physical such as through water, wind, Pressure, ice and temperature, or Chemical which involves changes in the chemical composition of the rock. There are a number of factors that influence the rate, type and quality of soil formed in a location.

F ACTORS OF SOIL FORMATION:

There are five factors that determine or influence soil formation, namely:

1. Parent material
2. Climate
3. Topography
4. Living organisms
5. Time

Parent material: The type of materials, that is structure, texture, and mineral composition present in the parent rock will also determine the type of soil formed Parent materials are important in the following ways:

1. Determining the properties of the soil e.g coarse, grain soils are formed from granite or gneiss
2. Coarse parent materials form coarse-textured and well-drained soils.
3. Rocks containing calcite, feldspar will produce deep heavy soils like clayey soils.
4. Quartz, Hornblende and mica will form poor soils like sandy soils.
5. Shale and limestone parent materials produce soils that are fine-textured, poorly drained and with high mineral content.

Climate: – This the average weather condition of a place over a long period of time.

Climatic factors include the following:

1. Rainfall
2. Temperature

• Wind

1. Relative humidity
2. Pressure
3. Cloud cover

• Sunlight

Rainfall: Helps in the dissolution of chemicals from the parent materials and also in transporting broken down materials.it determine the types of soil to be formed

Temperature:  Effect of temperature leads to expansion and contraction of rocks. Rock mineral with low expansively will break away to form soil. Also, rock holes may retain water which freezes up at night and melts during the day, leading to disintegration of rocks and eventually soil formation.

 TOPOGRAPHY:

Relief or topography refers to the surface features of the earth crust such as hills, valleys or flat land. It may also mean the shape of the land in relation to the underlying rocks of the

earth surface. The effect may include the following:

1. The shape of the land affects the movement and amount of water in the soil.
2. Hilly and sloppy surfaces support erosion and encourage soil formation. A flat land exposes the surface to equal environmental factors and therefore delays soil formation. However there maybe rapid accumulation of soil in the valley.

LIVING ORGANISMS:

This refers to the activities of plants, microbes, rodents, man. Their effects will help to encourage soil formation in the following ways;

Animals such as rodents, earthworms, termite, etc burrow into the rocks, thereby leaving the holes or

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