5.3 Soil degradation and conservation

Question 1

What is the definition of “soil degradation”?

Answer 1

“The partial of total loss of productive capacity of the soil, which ultimately leads to desertification”

Question 2

What is the definition of “desertification”?

Answer 2

“The severe degradation of semi-arid land into desert. Can cause crop failure and lead to malnutrition and famine.”

Question 3

What are the two types of soil degradation?

Answer 3

Erosion:
- Due to wind or water
- Occurs mainly when lack of vegetation

Making soil unusable
- Pollutants
- Leaching of nutrients

Question 4

In what ways can human activity lead to soil degradation?

Answer 4

• Deforestation
  –> The more vegetation (eg. trees) removed, the more prone to erosion
• Intensive grazing
  –> Too many animals grazing in the same area - plants can’t recover - leads to bare patches
• Urbanisation
  –> More people living in cities
  –> Increased run off could lead to extra erosion downstream
• Unsustainable agriculture
  –> Over use of land/ too many crops
  –> The chemical and energy inputs usually alter the natural environment (deteriorates soil quality and eliminates biodiversity)
  –> Irrigation methods (salinization)
  –> Plowing fields in direction of slope (it creates channels and facilitates water erosion!)

Question 5

What are the processes of soil degradation?

Answer 5

• Soil erosion
  –> Movement of soil components (especially surface litter and topsoil). Due to either water or wind usually.
• Salinization
  –> The concentration of soluble salts in the upper layers of soil
  –> Stunts crop growth, lowers crop yields
  –> Poorly designed irrigation may also contribute to this. If existing drainage cannot handle the increased water supply, water logging occurs and ground water rises bringing dissolved salts to the surface.

Question 6

What soil conservation methods can be used to reduce/ prevent soil degradation?

Answer 6

• Use of soil conditioners
  –> Crushed limestone or chalk is scattered on the soil to increase pH of acidic soils which arise due to acid deposition (neutralisation)
  –> Also helps clay particles stick together increasing drainage and aeration
  –> VERY EXPENSIVE! ANE NEEDS TO BE APPLIED CONSTANTLY
• Wind reduction techniques
  –> Planting trees or bushes to create wind breaks and shelter belts
• Good irrigation management
  –> By careful planning and construction of irrigation systems, evaporation and therefore salinisation can be strongly reduced
  –> Switching to more efficient methods such as drip irrigation

Question 7

What is agroforestry and why is it beneficial for soils?

Answer 7

Grow traditional crops in between high value timber and fruit trees
–> Trees have deeper roots –> better maintenance of soil quality
+ greater biodiversity!