AGRICULTURAL SCIENCE

THEME: AGRICULTURE ECOLOGY 

CLASS – SENIOR SECONDARY SCHOOL (SSS 1)

PREVIOUS LESSON – Agricultural Science Plan Lesson Notes for Senior Secondary Schools – SSS 1

 

TOPIC – SOIL

LEARNING AREA

1. Types (Meaning) of Soil

2. Chemical Elements in the Soil

3. Physical Properties of Soil

4. Soil pH

 

PERFORMANCE OBJECTIVES 

By the end of the lesson, most of the students should have attained the following objectives –

1. Recognise the different types of soil.

2. Name the chemical elements in the soil that constitute plant nutrients.

3. Name soil microbes and other soil inhabiting organisms.

4. Determine the pH of different soil types.

 

INSTRUCTIONAL MATERIALS

The teacher will teach the lesson with the aid of:

1. Diagram of soil profile.

2. Dug or existing soil profile.

 

REFERENCE MATERIALS

1. Scheme of Work

2. National Curriculum SSS Classes

3. Course Book

4. All Relevant Material

5. Online Information

 

CONTENT OF THE LESSON

INTRODUCTION

Soil is the top layer of the earth’s surface which made up of living and non living things. That’s, it is a mixture of minerals, organic matter, water, air, and living organisms that forms the top layer of the earth’s surface. It is essential for plant growth and provides nutrients, water, and physical support for plants to grow healthy. Soil is a complex ecosystem that plays a crucial role in sustaining life on Earth.

 

COMPOSITION OF SOIL

Soil is made up of living and non things such as –

1. Water

2. Leaf litters

3. Rocks, humus

4. Dead animals

5. Living animals

6. Air

7. Soil particles – sand, loam and clay.

 

TYPES OF SOIL

Soil can be classified into three primary types based on its texture –

1. Sandy soil

2. Clay soil

3. Loamy soil

 

1. SANDY SOIL

Sandy soil is a loose soil which made of small pieces of rocks and minerals. It has several economic benefits and applications in agriculture, construction, water management, and environmental protection. Its unique properties make it a valuable resource for various industries and contribute to sustainable economic development.

 

CHARACTERISTICS OF SANDY SOIL

The characteristics of sandy soil are as follows –

1. Sandy soil is characterized by its large particles and low fertility levels.

2. It has a gritty texture and poor water retention, which means it dries out quickly.

3. Sandy soil has good drainage due to the large spaces between particles, which can help prevent waterlogging.

4. This type of soil warms up quickly in the spring, making it suitable for plants that require warm temperatures to thrive.

5. Sandy soil is often acidic, but it can be easily amended with organic matter or lime to adjust the pH levels.

6. This type of soil is suitable for drought-tolerant plants that can withstand the rapid drainage and low water-holding capacity.

7. Sandy soil is easy to work with and cultivate, making it ideal for gardening and landscaping projects.

8. It tends to lack essential nutrients such as nitrogen, potassium, and phosphorus, requiring regular fertilization to support plant growth.

9. Sandy soil is prone to erosion and nutrient leaching, so it may need additional measures like mulching or cover crops to prevent soil depletion.

10. Despite its limitations, sandy soil can be productive with proper care and management practices.

 

ECONOMICS IMPORTANCE OF SANDY SOIL 

Sandy soil is a type of soil that has larger particles and is generally well-draining. While sandy soil may have some limitations, it also has several economic benefits:

1. Sandy soil is usually very well-draining, which can be beneficial for crop production. This type of soil allows for the easy movement of water and air, which can prevent waterlogging and promote healthy root growth in plants. Sandy soil is also easy to till and work with, making it more cost-effective for farmers.

2. Sandy soil is commonly used in construction for backfilling, creating filler material, and as a base for roads and buildings. Its stability and good drainage properties make it a suitable choice for construction projects, especially in areas prone to heavy rainfall.

3. Sandy soil is often used in filtration systems to remove impurities from water. Its porous nature allows water to pass through easily, making it an excellent choice for wastewater treatment facilities and septic systems.

4. Sandy soil plays a crucial role in protecting coastal areas from erosion. It can help stabilize sand dunes and provide a natural barrier against storm surges and flooding. Sandy beaches are also significant economic assets for tourism and recreation industries.

 

CLAY SOIL

Clay soil is gray or red soil that small and closely packed particles. It plays a crucial role in various industries and provides economic benefits to societies around the world. Its unique properties make it a valuable resource for agriculture, construction, and other sectors, contributing to the overall economic development of a region.

 

CHARACTERISTICS OF CLAY SOIL

The characteristics of clay soil are follow –

1. Clay soil has very small particles that are tightly packed together, resulting in poor drainage and slow water infiltration.

2. It is sticky and easily compacted when wet, making it hard for plant roots to penetrate and grow.

3. Clay soil has a high nutrient content, which can be beneficial for plants once they are able to establish root systems.

4. It holds moisture well, which can be both a benefit and a drawback depending on the plants being grown.

5. Clay soil tends to be more alkaline, with a pH level ranging from 7.0 to 9.0, which can impact plant growth and nutrient availability.

6. Due to its high nutrient content and ability to retain water, clay soil can be fertile and productive for certain types of plants.

7. Clay soil is heavy and can be difficult to work with, especially when wet, as it easily becomes compacted and hard to dig.

8. It requires proper soil management practices, such as adding organic matter and using proper techniques for planting and watering, to improve its structure and fertility for plant growth.

 

ECONOMIC IMPORTANCE OF CLAY SOIL

Clay soil, which is characterized by its small particle size and high water-retention capacity, has several economic importance:

1. Clay soil is known for its fertility and ability to retain nutrients, making it ideal for growing a wide variety of crops. Farmers often use clay soil to grow crops such as wheat, barley, corn, and soybeans.

2. Clay soil is commonly used in construction for making bricks, tiles, and pottery. Its plasticity allows it to be molded into different shapes and forms, making it a versatile material for building structures.

3. Clay soil is used in landscaping for its ability to hold moisture and provide a stable base for plants. It is often used as a natural barrier to prevent erosion and as a foundation for gardens and lawns.

4. Clay soil is also an important resource for the mining industry, as it contains valuable minerals such as kaolinite, montmorillonite, and illite. These minerals are used in various industries, including ceramics, paper production, and pharmaceuticals.

5. Clay soil has the high water-retention capacity which makes it a valuable resource for water management. Clay soil helps to regulate water flow and prevent erosion, making it essential for maintaining healthy ecosystems and agricultural productivity.

 

LOAMY SOIL

Loamy soil is made of equal amount of sandy and clay soil. It plays a crucial role in agriculture, construction, landscaping, and environmental conservation. Its balanced composition and fertile nature make it a valuable resource for various industries, contributing to economic growth and development.

 

CHARACTERISTICS OF LOAMY SOIL

The characteristics of loamy soil are as follows –

1. Loamy soil is a mixture of sand, silt, and clay particles, with the ideal proportion being equal parts of each. It is considered to be the best soil type for gardening and agriculture.

2. It has a good balance of drainage and water retention, allowing for adequate moisture levels for plant growth without waterlogging.

3. Loamy soil is easily workable and has a loose, crumbly texture that allows plant roots to penetrate and grow deeply.

4. It is rich in nutrients and has a high organic matter content, providing a fertile environment for plant growth.

5. Loamy soil has a neutral pH level, which is optimal for most plants to access essential nutrients.

6. It warms up quickly in the spring, allowing for early planting and extended growing seasons.

7. It has good aeration, which promotes healthy root development and microbial activity in the soil.

8. Loamy soil is less prone to compaction than clay soil, making it easier to cultivate and maintain for gardening and farming purposes.

 

ECONOMIC IMPORTANCE OF LOAMY SOIL

Loamy soil, which is a mixture of sand, silt, and clay, is considered the ideal soil type for agriculture due to its balanced composition of different soil particles. Here are some of the economic importance of loamy soil:

1. Loamy soil is highly fertile and well-draining, making it ideal for growing a wide variety of crops. Farmers often prefer loamy soil for cultivating crops such as fruits, vegetables, grains, and cash crops. The balanced composition of loamy soil provides a good balance of water retention and drainage, facilitating optimal plant growth and high yields.

2. Loamy soil is commonly used in landscaping and gardening due to its ability to support plant growth. Its well-draining nature helps prevent waterlogging, while its fertility allows for lush plant growth. Landscapers and gardeners often use loamy soil to create beautiful and sustainable outdoor spaces.

3. Loamy soil can also be used in construction for building foundations and roadbeds. Its stable structure and good drainage properties make it a suitable material for supporting structures and infrastructure projects.

4. Loamy soil is effective in preventing soil erosion due to its balanced composition and ability to retain moisture. It is often used in erosion control measures such as terracing, contour plowing, and planting cover crops to protect vulnerable areas from soil loss.

5. The balanced composition of loamy soil allows it to effectively manage water, making it a valuable resource for water-sensitive industries. Loamy soil helps regulate water flow, prevent runoff, and maintain healthy water systems, making it essential for sustainable water management practices.

 

CHEMICAL AND BIOLOGICAL COMPOSITION OF SOIL

Soil is a complex mixture of mineral particles, organic matter, water, air, and living organisms. The chemical and biological composition of soil can vary depending on factors such as climate, vegetation, land use, and soil type. Soil composition is a dynamic and intricate system that supports plant growth, nutrient cycling, and ecosystem function. Understanding the chemical and biological components of soil is essential for sustainable land management practices, agriculture, and environmental conservation. Here are some key components of soil composition

A. CHEMICAL COMPOSITION

1. Mineral particles – Soil is composed of different mineral particles, mainly sand, silt, and clay. The proportion of these particles determines the texture of the soil, affecting its water-holding capacity, drainage, and fertility.

2. Organic matter – Organic matter in soil includes plant and animal residues in various stages of decomposition. It provides essential nutrients for plant growth, improves soil structure, retains moisture, and supports the soil microbial community.

3. Nutrients – Soil contains essential nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, which are vital for plant growth and development. These nutrients are derived from organic matter, mineral weathering, and fertilizers.

4. pH – The pH of soil influences nutrient availability and microbial activity. Soil pH is a measure of acidity or alkalinity, with most plants preferring a slightly acidic to neutral pH range for optimal growth.

 

B. BIOLOGICAL COMPOSITION

1. Microorganisms – Soil is home to a diverse community of microorganisms, including bacteria, fungi, protozoa, and nematodes. These microorganisms play key roles in nutrient cycling, organic matter decomposition, and plant-microbe interactions.

2. Soil fauna – Soil fauna such as earthworms, insects, mites, and microarthropods contribute to soil health by aerating the soil, breaking down organic matter, and enhancing nutrient cycling.

3. Plant roots – Plant roots interact with the soil environment to uptake water and nutrients, anchor plants, and support soil structure. Root exudates also influence soil microbial communities and nutrient availability.

4. Soil structure – Soil structure refers to the arrangement of soil particles into aggregates or clumps. A healthy soil structure allows for good water infiltration, root penetration, and air exchange, promoting plant growth and microbial activity.

 

SOIL pH

Soil pH is a measure of how acidity or alkalinity the soil is. It is important for plant growth because it affects the availability of nutrients. Soil pH is measured on a scale of 1-14, with 7 as the neutral mark. Most plants prefer a slightly acidic soil with a pH level between 6 and 7. If the soil is too acidic or too alkaline, it can affect the plant’s ability to take up nutrients, leading to stunted growth or nutrient deficiencies. Testing the soil pH and adjusting it if necessary can help ensure healthy plant growth.

 

PHYSICAL PROPERTIES OF SOIL

The physical properties of soil interacting with each other create a complex environment that supports plant growth and ecosystem functions. Understanding and managing these properties is important for sustainable agriculture and environmental conservation. Some of the key physical properties of soil include:

1. Texture – Soil texture refers to the size of the mineral particles in the soil, which can range from sand (largest particles) to clay (smallest particles). Soil texture affects water retention, drainage, and aeration.

2. Structure – Soil structure refers to how soil particles are grouped together into aggregates. The arrangement of these aggregates affects the porosity, water infiltration, and root penetration in the soil.

3. Porosity – Porosity is the amount of pore space in the soil, which affects water retention and drainage. Soil with high porosity allows water and air to move freely, while low-porosity soil may become waterlogged.

4. Bulk Density – Bulk density is a measure of how tightly packed the soil particles are. High bulk density can restrict root growth and water infiltration, while low bulk density can lead to poor soil structure.

5. Moisture Content – The moisture content of soil is important for plant growth, as it affects nutrient availability and root growth. Soil that is too dry can lead to drought stress, while waterlogged soil can suffocate roots.

6. Color – Soil color can indicate the presence of certain minerals or organic matter. Darker soils tend to be rich in organic matter, while reddish soils may indicate the presence of iron oxides.

7. pH – Soil pH is a measure of the acidity or alkalinity of the soil, which can affect nutrient availability to plants. Most plants prefer a slightly acidic soil pH between 6 and 7.

 

PRESENTATION

To deliver the lesson, the teacher adopts the following steps:

1. To introduce the lesson, the teacher revises the previous lesson. Based on this, he/she asks the students some questions; then, the teacher –

2. Displays soil samples e.g. loamy, sandy, clayey.
Conduct pH tests.

Student’s Activities – Examine the soil samples and determine their physical characteristics. Carry out laboratory experiments as directed.

3. Summarizes the lesson on the board.

Student’s Activities – Copy as the teacher writes.

 

CONCLUSION

To conclude the lesson for the week, the teacher revises the entire lesson and links it to the following week’s lesson.

 

LESSON EVALUATION 

Teacher asks students to:

1. Mention types of soil.

2) State major composition of soil. V – conduct laboratory experiment to determine any one of each.

3) Discuss biological and chemical properties of soil.

4) How will you determine physical properties of soil e.g. soil texture, soil structure, soil air, etc.

5) Determine pH of any two soil types.

 

HOW WILL YOU DETERMINE PHYSICAL PROPERTIES OF SOIL?

There are various methods and tests that can be used to determine the physical properties of soil. Some common methods include:

1. Texture Analysis – Soil texture can be determined by feeling the soil, but more accurately by using the hydrometer method or sieve analysis to measure the percentages of sand, silt, and clay present in the soil.

2. Bulk Density Measurement – Bulk density is the mass of soil per unit volume and can be determined by collecting soil samples and weighing them.

3. Porosity Measurement – Porosity is the percentage of pore space in soil and can be determined using methods such as the water displacement method or calculating from bulk density and particle density.

4. Soil pH Measurement – Soil pH can be measured using a pH meter or test kit to determine the acidity or alkalinity of the soil.

5. Moisture Content Measurement – Soil moisture content can be determined by drying soil samples in an oven and calculating the percentage of water lost.

6. Soil Color Analysis – Soil color can provide information about the composition and organic matter content of soil and can be determined using a Munsell soil color chart.

7. Compaction Testing – Soil compaction can be measured using methods like the Proctor test or the sand cone test to determine the soil’s ability to support structures.

 

HOW TO DETERMINE THE PH OF DIFFERENT TYPES OF SOIL?

To determine the pH of different soil types, you can follow these steps:

1. Collect soil samples from different locations or types of soil that you want to test. Use a soil auger or shovel to collect samples from various depths (0-6 inches is recommended).

2. Dry the soil samples by spreading them out on a paper or tray and letting them air dry for a few days. Make sure the samples are completely dry before proceeding.

3. Crush the dried soil samples to a fine powder using a mortar and pestle or a grinder.

4. Take a small amount of the crushed soil sample and mix it with distilled water in a clean container. Use a soil to water ratio of about 1:2. Stir the mixture well and let it sit for about 30 minutes.

5. After 30 minutes, use a pH testing kit or a pH meter to measure the pH of the soil-water mixture. Follow the instructions provided with the testing kit or meter for accurate readings.

6. Repeat the process for each soil sample you collected to determine the pH of different soil types.

7. Analyze the pH results and compare them to determine the acidity or alkalinity of each soil type. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline.

Note – Clean all equipment thoroughly between each sample to prevent cross-contamination and ensure accurate results.