3.2.5 Soils

Question 1

Factor affecting fertility

Answer 1

• aeration of soil by ploughing and drainage
• addition of soil nutrients
• irrigation
• soil compaction, increasing bulk
density
• pH control.

Question 2

Soil segregation and erosion

Answer 2

Types of soil erosion:
• rain splash
• wind blow
• surface runoff.
Natural features that reduce erosion:
• vegetation
• soil organic matter
• high infiltration rate.
The Universal Soil Loss Equation (USLE) can be used to estimate erosion rates.
Human activities that cause soil erosion and degradation:
• ploughing vulnerable soils
• vegetation removal
• overgrazing
• reducing soil organic matter
• reducing soil biota
• cultivating steep slopes
• soil compaction by machinery or
trampling.
The environmental impacts of soil erosion:
• reduced productivity
• sedimentation in rivers and
reservoirs
• downstream flooding
• coastal sedimentation
• increased atmospheric particulates
• desertification
• landslides.

Question 3

Methods to reduce erosio

Answer 3

• long-term crops
• contour ploughing
• tied ridging
• terracing
• windbreaks
• multicropping
• strip cropping
• mulching
• increasing soil organic matter.