5. Soil Systems and Terrestrial Food Production Systems and Societies

What are the main components of soil?

Soil is made up of mineral particles, organic matter (humus), water, air, and living organisms such as fungi, bacteria, and worms. These components interact to support plant growth and nutrient cycling.

What is a soil horizon, and what are the typical layers?

Soil horizons are layers in a soil profile, each with distinct properties:

• O horizon: organic matter

• A horizon: topsoil (minerals + organic material)

• B horizon: subsoil (accumulated minerals)

• C horizon: weathered parent material

• R horizon: unweathered bedrock

How is soil texture determined and why does it matter?

Soil texture is based on the percentage of sand, silt, and clay. It affects drainage, aeration, water retention, and nutrient availability, influencing crop suitability and soil management.

What are the characteristics of clay, silt, and sand particles in soil?

• Clay: tiny particles, high water-holding capacity, poor drainage

• Silt: medium-sized, smooth texture, retains moisture well

• Sand: large particles, good drainage, poor at retaining water and nutrients

What are soil ecosystem services?

Soil provides vital services including:

• Nutrient cycling (decomposition and mineralization of organic material)

• Water filtration and purification

• Habitat for organisms (micro and macro)

• Climate regulation through carbon sequestration

• Support for plant growth, forming the base of terrestrial food chains
  Healthy soils are essential for agriculture, biodiversity, and combating climate change.

What are the major inputs and outputs in a soil system?

Inputs: organic matter (e.g. dead plants), precipitation, mineral particles from weathering, artificial fertilizers.
Outputs: erosion, leaching, uptake by plants, gaseous losses through respiration and denitrification.

What are common causes of soil degradation?

Soil degradation occurs through:

• Erosion (wind/water removing topsoil)

• Overgrazing (removes vegetation, increases compaction)

• Deforestation (loss of root structures that hold soil)

• Overcultivation (depletes nutrients, causes compaction)

• Salinization (from poor irrigation practices)

• Acidification (from acid rain or fertilizer use)

• Pollution (pesticides, heavy metals, industrial waste)

What are some methods to prevent or reduce soil degradation?

• Contour ploughing: reduces runoff by following land contours

• Terracing: slows water runoff on slopes

• Cover cropping: protects soil from erosion and restores nutrients

• Crop rotation: maintains soil fertility and prevents pest buildup

• Agroforestry: integrates trees with crops for shade and root stability

• Composting and mulching: improve organic matter and soil structure

• Reduced tillage: minimizes disturbance to soil layers
  All these practices enhance soil health and long-term productivity.

What is the difference between arable and pastoral farming?

• Arable farming: cultivation of crops

• Pastoral farming: raising animals for meat, milk, or wool
  Arable farming often requires more soil preparation, while pastoral farming can lead to overgrazing and compaction.

What are commercial vs. subsistence farming systems?

• Commercial farming: large-scale, profit-oriented, often mechanized

• Subsistence farming: small-scale, focused on feeding the farmer’s household, minimal surplus for trade

What are the environmental impacts of industrialized agriculture?

Impacts include:

• Loss of soil fertility

• Soil erosion from over-tillage

• Water pollution from fertilizer and pesticide runoff

• Greenhouse gas emissions

• Biodiversity loss from monocultures and habitat destruction

What are some factors that influence food production systems?

Climate, terrain, soil quality, access to water, technology, socio-economic conditions, market demand, and policy all affect food production.

How does food production relate to energy efficiency?

Producing food from lower trophic levels (e.g. plants) is more energy-efficient than meat due to energy losses between trophic levels. Industrial agriculture may also rely heavily on fossil fuels.

What is the concept of food security?

Food security exists when all people have access to enough safe, nutritious food to meet their dietary needs and preferences for an active, healthy life.

What are the main barriers to global food security?

Conflict, poverty, climate change, food waste, poor infrastructure, and unequal access to land and markets.

What are the benefits and drawbacks of organic farming?

Benefits: improves soil health, reduces pollution, no synthetic inputs, supports biodiversity
Drawbacks: lower yields, higher labor input, more land required, premium pricing

What are the differences between intensive and extensive agriculture?

• Intensive: high input/output per unit area, mechanized, often monoculture

• Extensive: low input/output per unit area, large land areas, less technology-dependent

How can sustainable soil management support food security?

Sustainable management practices (e.g. crop rotation, reduced tillage, cover crops, composting) maintain soil fertility, prevent erosion, and ensure long-term productivity—essential for consistent food supply.