5.3_soil_degradation_and_conservation

Overview

  • Soil degradation refers to the decline in soil quality and productivity, often caused by various human activities and natural processes.

  • Conservation of soil is essential to maintain its health and productivity.

Soil Types Based on Degradation Levels

  • Very Degraded Soil: Severe loss of nutrients and structure, incapable of supporting vegetation.

  • Degraded Soil: Some loss of nutrients, still has limited ability to support certain types of vegetation.

  • Stable Soil: Healthy soil structure and nutrient content, capable of supporting a diverse range of plant life.

Causes of Soil Degradation

Processes Leading to Soil Degradation

  • Soil Erosion: Removal of topsoil, making it less suitable for growing crops.

  • Chemical Contamination: Increase in harmful chemicals, leading to decreased soil viability.

Human Activities Contributing to Soil Degradation

  1. Overgrazing:

    • Roots fail to hold soil particles, leading to dry conditions and wind erosion.

  2. Overcropping:

    • Nutrient depletion occurs, resulting in dry soil worsened by wind erosion.

  3. Deforestation:

    • Increased risk of water erosion due to lack of plant cover.

  4. Urbanization:

    • Land development leads to soil compaction and surface sealing.

  5. Unsustainable Agriculture Practices:

    • Practices that do not maintain soil health over time.

  6. Salinization from Irrigation:

    • Accumulation of salts in the soil, rendering it unproductive.

  7. Excessive Pesticide Use:

    • Disruption of soil microbial life and chemistry.

  8. Monocultures:

    • Growing the same crop repeatedly depletes specific soil nutrients.

  9. Cultivation on Slopes:

    • Increases erosion risk due to runoff.

Major Processes of Soil Erosion

  1. Sheet Wash:

    • Thin layers of soil washed away during heavy rainfall events.

  2. Gullying:

    • Formation of deep channels on hillsides, which erodes large areas of soil.

    • Example: Nanka gully in Nigeria, 1100 km² long.

  3. Wind Erosion:

    • Dry topsoil is blown away, leading to loss of fertile ground.

Soil Formation

  • Soil formation is a slow process often influenced by the following:

    • Time: Takes necessary time to develop soil layers.

    • Organisms: Living organisms contribute to soil structure and nutrient cycling.

Soil Conservation Strategies

  1. Addition of Soil Conditioners:

    • Incorporating lime to adjust pH levels; drainage is enhanced by larger particles.

  2. Wind Reduction Techniques:

    • Use of fences or planting trees and bushes to protect fields from wind.

  3. Soil Conserving Cultivation Techniques:

    • Utilizing cover crops, terracing to avoid slopes, and plowing for better drainage.

    • Contour Farming: Plowing along the contour of the land to reduce erosion.

  4. Improved Irrigation Techniques:

    • More efficient systems to minimize salinization and ensure soil health.

  5. Avoid Plowing Marginal Lands:

    • Protect soil structure and promote microbial activity in unsuitable biomes (e.g., deserts).

  6. Crop Rotation:

    • Alternating crops to restore soil nutrients and health.

Homework Assignments

  • Evaluate soil management strategies in:

    • A named commercial farming system.

    • A named subsistence farming system.

  • Explain the relationship between soil ecosystem succession and soil fertility.

  • Refer to specific pages and case studies for guidance on these evaluations.