Millennium Elearning Centre
UNIT 1: SOIL DEGRADATION
MSCE Form 4 Agriculture Study Guide
Definition
Soil degradation is the loss in value and quality of soil.
Forms of Soil Degradation
Physical Degradation
Causes:
Soil is physically destroyed through the impact of heavy rainfall and the use of machinery in agricultural practices.
Characteristics:
- Poor Drainage: Soil compaction leads to reduced permeability, making it difficult for water to infiltrate.
- Poor Porosity: Compacted soil has reduced pore spaces, limiting air and water movement.
- Reduced Water-Holding Capacity: The ability of soil to retain moisture diminishes, adversely affecting plant growth.
Chemical Degradation
Causes:
- Use of Agrochemicals: Overreliance on fertilizers and pesticides can lead to soil contamination and toxicity, impacting soil health.
- Salination: The excessive use of chemical fertilizers may cause salinity, which depletes essential nutrients and reduces crop yields.
Causes of Soil Degradation
Deforestation
The removal of trees disrupts the natural cycle, leading to erosion and loss of organic matter.
Bad Farming Practices
Unsustainable agricultural techniques, such as monocropping and over-tillage, contribute to soil degradation.
Irrigation & Soil Drainage
Poorly managed irrigation practices can cause the accumulation of acids and salts, harming soil health.
Leaching
Nutrient loss occurs when rainwater washes vital minerals deeper into the soil, making them unavailable to plants.
Soil Compaction
Heavy machinery and excessive foot traffic compact the soil, reducing its ability to hold air and water.
Effects of Soil Degradation
Soil Erosion
The removal of the topsoil layer, which is crucial for plant growth.
Loss of Soil Fertility
Degraded soil becomes less capable of supporting crops due to nutrient depletion.
Poor Soil Structure
Degradation leads to the breakdown of soil aggregates, affecting water infiltration and root growth.
Flooding
Compacted and poorly draining soil increases runoff, leading to flooding in surrounding areas.
Silting
Erosion can result in sediment deposition in rivers and lakes, harming aquatic ecosystems.
Water Pollution
Chemicals from degraded soils can leach into water bodies, contaminating freshwater resources.
Reduced Arable Land
The overall land area suitable for agriculture decreases, impacting food production.
Spread of Weeds
Degraded conditions may promote the growth of invasive weed species, which compete with crops for resources.
Loss of Fertile Topsoil
The uppermost layer of soil, which is rich in nutrients, is most vulnerable to erosion and degradation.
Population and Soil Degradation
Growing population creates increasing pressure on soil resources through various demands:
Demand for Wood Fuel
Increasing population leads to higher wood consumption, resulting in deforestation and habitat loss.
Need for Shelter & Furniture
Urban expansion and construction activities contribute to land degradation and soil loss.
Demand for Fiber
The cultivation of fiber crops like sisal and cotton can lead to soil depletion if not managed sustainably.
Need for More Food
Growing populations drive the demand for food production, often leading to intensified agricultural practices that degrade soil.
Ways to Control Soil Degradation
A) Biological Methods
Planting Trees
Reforestation helps restore ecosystems, enhance soil stability, and improve water retention.
Planting Cover Crops
These crops protect the soil surface, reduce erosion, and improve soil fertility.
Grassed Waterways
Vegetation in waterways helps filter runoff and reduce erosion.
Contour Farming
Farming along the contour lines of slopes minimizes soil loss and enhances water retention.
Mulching
Applying organic materials on the soil surface retains moisture, suppresses weeds, and adds organic matter.
B) Physical Methods
Stone Lines
Constructing lines of stones helps slow down water runoff and reduce erosion.
Trash Lines
Heaps of crop residues can trap sediments, preventing soil loss and improving moisture retention.
Ridging
Creating ridges enhances drainage and allows for better water absorption in crops.
Study Tips for MSCE Success
🎯 Key Concepts
Focus on understanding the difference between physical and chemical degradation, and memorize all causes and effects.
📝 Exam Strategy
Practice drawing diagrams showing soil degradation processes and control methods. Use real examples from Malawi.
💡 Memory Tips
Create acronyms for causes (DIBILS: Deforestation, Irrigation, Bad farming, Leaching, Soil compaction).
