Back to: Botany 200 Level
Hello, my brilliant student! I hope you’re doing great today! Have you ever noticed how some plants grow well in certain soils while others struggle? Just like humans need a balanced diet to stay healthy, plants need the right soil composition to get the nutrients they need. Today, we’ll explore what soil is made of and how it affects plant nutrition.
Soil Composition and Its Impact on Plant Nutrition
Soil is much more than just sand and dirt—it’s a mixture of minerals, organic matter, water, air, and living organisms. These components determine how well plants grow and how easily they can absorb nutrients.
Components of Soil
Mineral Particles (45%)
Made up of sand, silt, and clay.
Provides structure and stores essential minerals like potassium (K), phosphorus (P), and calcium (Ca).
The ratio of these particles determines the soil type (sandy, loamy, or clayey).
Organic Matter (5%)
Decomposed plant and animal material (humus).
Improves soil fertility by supplying nutrients like nitrogen (N).
Helps retain water and supports beneficial microorganisms.
Water (25%)
Dissolves nutrients so plants can absorb them.
Affects root growth and soil moisture levels.
Air (25%)
Oxygen is needed for root respiration and microbial activity.
Well-aerated soil allows roots to grow and function properly.
Living Organisms (Microbes, Earthworms, Fungi)
Microorganisms break down organic matter to release nutrients.
Earthworms improve soil structure and increase aeration.
Mycorrhizal fungi help roots absorb water and minerals more efficiently.
How Soil Affects Plant Nutrition
Nutrient Availability
Sandy soil loses nutrients quickly, so plants may not get enough food.
Clay soil holds nutrients well, but if too compact, roots can’t access them easily.
Loamy soil provides the best balance of nutrients and moisture.
Water Retention
Too much water (clay soil) can drown roots.
Too little water (sandy soil) can cause drought stress.
pH Levels
Some nutrients become unavailable if the soil is too acidic or too alkaline.
Most plants prefer a pH between 6.0 and 7.5.
Microbial Activity
Healthy soil has microbes that break down organic matter into plant-usable nutrients.
Improving Soil for Better Plant Nutrition
Adding Organic Matter (compost or manure) improves fertility.
Using Mulch reduces water loss and prevents nutrient leaching.
Adjusting Soil pH (lime for acidic soil, sulphur for alkaline soil) ensures nutrient availability.
Planting Cover Crops (like legumes) adds nitrogen naturally.
Summary
Soil is made up of minerals, organic matter, water, air, and organisms.
Different soil types affect water retention, nutrient availability, and plant growth.
Loamy soil is the best for plant nutrition as it holds nutrients and water well.
Soil pH, microbes, and organic matter all influence how well plants absorb nutrients.
Farmers and gardeners improve soil using compost, mulch, and pH adjustments.
Evaluation
- What are the five components of soil?
- Why do plants struggle in sandy soil?
- How does organic matter improve soil fertility?
- What is the best soil type for plant growth? Why?
- How does soil pH affect nutrient availability?
Well done! Now you understand how soil composition affects plant nutrition. Plants depend on healthy soil just like we depend on healthy food. Keep learning—Afrilearn is here to make learning fun and easy! See you in the next lesson!
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