TOPIC 5: SOIL
SYSTEMS AND
TERRESTRIAL FOOD
PRODUCTION
, 1. Introduction to soil systems
Soil systems
KEY CONCEPTS → Soil: a mixture of inorganic mineral particles and organic material from
decomposed flora and fauna that covers the underlying bedrock, and in which a wide variety of
terrestrial plants grow.
Parent rock: the upper layer of rock on which soil forms under the influence of biological and
biochemical processes and human activity. The properties of the parent rock are changed in the
process of soil formation through the effect of other soil-formation factors, but to a large extent the
properties of the parent rock still determine the properties of the soils.
Parent rock contributes to soil:
- Depth - Drainage
- Texture - Quality
- Colour
Soil formation
- Soils form due to the interaction between the lithosphere, biosphere, atmosphere and
hydrosphere.
Living organisms provide the organic component of a fertile soil through their death and decay
- Fertile soil: soil that is rich in the nutrients necessary for basic plant nutrition, including
nitrogen, phosphorus and potassium.
The atmosphere is a vital part of the soil formation process:
- The zonal classification of soil states that on a global scale soils are determined by climate.
- Soil is more prevalent in environments of high moisture and high temperatures than in cold,
dry regions. Increases moisture → erosion. Higher temperature → breakdown of organic
material.
- When organic material breaks down, it forms humus: dark brown or black substance made up
of decayed plant or animal matter. It provides nutrients for plants and increases the ability of
soil to retain water.
Precipitation effectiveness is the balance between precipitation and potential evapotranspiration:
- It determines the direction of water movement within a soil.
- When precipitation is greater than the potential EVT, leaching occurs (natural process by
which water-soluble substances such as calcium are washed out from soil. This reduces the
fertility of a soil)
The soil profile
- Soil formation begins first with the breakdown of rock into regolith, which is the irregular
cover of loose rock debris that covers the Earth
SYSTEMS AND
TERRESTRIAL FOOD
PRODUCTION
, 1. Introduction to soil systems
Soil systems
KEY CONCEPTS → Soil: a mixture of inorganic mineral particles and organic material from
decomposed flora and fauna that covers the underlying bedrock, and in which a wide variety of
terrestrial plants grow.
Parent rock: the upper layer of rock on which soil forms under the influence of biological and
biochemical processes and human activity. The properties of the parent rock are changed in the
process of soil formation through the effect of other soil-formation factors, but to a large extent the
properties of the parent rock still determine the properties of the soils.
Parent rock contributes to soil:
- Depth - Drainage
- Texture - Quality
- Colour
Soil formation
- Soils form due to the interaction between the lithosphere, biosphere, atmosphere and
hydrosphere.
Living organisms provide the organic component of a fertile soil through their death and decay
- Fertile soil: soil that is rich in the nutrients necessary for basic plant nutrition, including
nitrogen, phosphorus and potassium.
The atmosphere is a vital part of the soil formation process:
- The zonal classification of soil states that on a global scale soils are determined by climate.
- Soil is more prevalent in environments of high moisture and high temperatures than in cold,
dry regions. Increases moisture → erosion. Higher temperature → breakdown of organic
material.
- When organic material breaks down, it forms humus: dark brown or black substance made up
of decayed plant or animal matter. It provides nutrients for plants and increases the ability of
soil to retain water.
Precipitation effectiveness is the balance between precipitation and potential evapotranspiration:
- It determines the direction of water movement within a soil.
- When precipitation is greater than the potential EVT, leaching occurs (natural process by
which water-soluble substances such as calcium are washed out from soil. This reduces the
fertility of a soil)
The soil profile
- Soil formation begins first with the breakdown of rock into regolith, which is the irregular
cover of loose rock debris that covers the Earth
