MEV 014: Unit 04 – Soil and Land Resources

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 UNIT 4: SOIL AND LAND RESOURCES

4.0 Introduction

Soil is a vital natural resource that supports life on Earth. It forms the upper layer of the Earth’s surface and plays a key role in agriculture, water filtration, plant growth, and biodiversity. Land resources include all components of the land—soil, minerals, water, vegetation, and landscapes. Together, soil and land form the foundation of human civilization, agriculture, and ecological balance.

However, with population growth and industrialization, soil and land resources face increasing pressure through overuse, pollution, and erosion. It is essential to understand their properties and ensure sustainable use and conservation.

4.1 Objectives

After completing this unit, you will be able to:

·         Define soil and describe its composition.

·         Understand the physical, chemical, and microbial properties of soil.

·         Identify the importance of soil in agriculture and ecosystems.

·         Explain the various uses of land and their impact on soil.

·         Understand causes and consequences of soil pollution.

·         Suggest ways to protect and manage soil and land resources sustainably.

4.2 What is Soil?

Soil is the topmost layer of the Earth’s crust formed by the weathering of rocks and the decomposition of organic matter over thousands of years. It is a mixture of minerals, organic matter, air, and water. Soil supports plant life and forms the base for agriculture and forests.

Major Components of Soil:

1.      Mineral particles – sand, silt, and clay.

2.      Organic matter – decomposed plant and animal remains (humus).

3.      Water – essential for plant growth and soil processes.

4.      Air – provides oxygen to roots and microbes.

5.      Microorganisms – bacteria, fungi, and earthworms.

4.3 Soil Physical and Chemical Properties

The quality and fertility of soil are determined by its physical and chemical properties. These properties vary with climate, vegetation, topography, and parent rock.

A. Physical Properties:

1. Texture:

·         Refers to the proportion of sand, silt, and clay.

·         Affects water-holding capacity and aeration.

·         Loamy soil is considered ideal for crops.

2. Structure:

·         The way soil particles are grouped.

·         Well-structured soil has good porosity and root penetration.

3. Porosity:

·         Determines the amount of air and water the soil can hold.

4. Moisture Content:

·         Important for plant growth.

·         Influences nutrient absorption.

5. Colour:

·         Indicates organic matter and mineral content.

·         Dark soil is generally fertile due to high humus.

B. Chemical Properties:

1. pH Level:

·         Shows acidity or alkalinity of soil.

·         Most crops prefer a pH between 6 and 7.5.

2. Cation Exchange Capacity (CEC):

·         Ability of soil to hold and exchange nutrients.

·         High CEC indicates good fertility.

3. Nutrient Content:

·         Includes macronutrients (N, P, K) and micronutrients (Zn, Fe, Mn).

·         Fertile soil has a balanced nutrient composition.

4.4 Soil Microbial Properties and Land Use

Soil Microbial Properties:

Soil is home to millions of microorganisms that help in nutrient cycling, decomposition, and soil fertility.

Types of Microbes in Soil:

1.      Bacteria: Decompose organic matter, fix nitrogen (e.g., Rhizobium).

2.      Fungi: Help in decomposition and nutrient absorption (e.g., Mycorrhiza).

3.      Actinomycetes: Decompose tough materials like cellulose.

4.      Protozoa and Algae: Contribute to soil health and nutrient flow.

Functions of Soil Microorganisms:

·         Decompose dead matter.

·         Fix atmospheric nitrogen.

·         Improve soil structure.

·         Suppress harmful pathogens.

Land Use and Its Effect on Soil:

Land is used for agriculture, forests, industries, housing, and infrastructure. However, improper land use causes:

·         Soil erosion

·         Loss of fertility

·         Waterlogging or desertification

·         Habitat destruction

Sustainable Land Use Practices:

·         Crop rotation and mixed farming

·         Afforestation and reforestation

·         Organic farming and composting

·         Terrace farming and contour ploughing in hilly areas

4.5 Soil and Its Pollution

Soil pollution refers to the presence of harmful chemicals or substances in the soil, which degrade its quality and affect plant and animal life.

Causes of Soil Pollution:

1.      Excessive use of chemical fertilizers and pesticides

2.      Industrial waste and heavy metals

3.      Urban waste and plastics

4.      Mining activities

5.      Oil spills and leakage of underground storage tanks

Consequences of Soil Pollution:

·         Loss of soil fertility

·         Contamination of groundwater

·         Bioaccumulation of toxins in food chain

·         Poor plant growth and crop yield

·         Harm to soil organisms and biodiversity

Control Measures:

·         Use of bio-fertilizers and organic manure

·         Reducing chemical usage

·         Proper waste management

·         Soil testing and remediation

·         Legislation and public awareness

4.6 Let’s Sum Up

·         Soil is a natural resource that supports plant life and is essential for agriculture, ecology, and water cycles.

·         It is composed of minerals, water, air, organic matter, and microorganisms.

·         Physical and chemical properties such as texture, moisture, pH, and nutrient content determine soil quality.

·         Microorganisms in the soil play a key role in maintaining its health and fertility.

·         Improper land use leads to degradation and pollution of soil.

·         Soil pollution is caused by chemicals, waste, and unsustainable practices.

·         Sustainable soil and land management are crucial for environmental health and food security.

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