Soil System & Man

Dynamic Earth

Course Title

  • Dynamic Earth GY4741

  • Soil System & Man

Lecture Outline

  1. The soil resource & classification

  2. Soil degradation, erosion & desertification

Soil Formation Factors

  • Climate

  • Biota

  • Topography

  • Parent material

  • Time

  • Human factor

Defining Soil

  • Ecocentric Definition:

    • Soil is defined by its capacity to function as a vital living system.

  • Anthropocentric Definition:

    • Soil is defined by its ability to sustain agricultural and arboreal productivity.

Soil as a Resource

Natural System Functions

  • Plant Growth: Supports vegetation.

  • Food, Fuel, and Energy: Provides resources necessary for life.

  • Water Storage: Holds and manages water resources.

  • Transmission and Filtration of Water: Filters and transmits water through the soil profile.

  • Biogeochemical Storage: Acts as a reservoir for chemical elements.

  • Decomposition and Organic Matter Recycling: Facilitates the breakdown of organic substances.

  • Nutrient Regulation: Regulates the nutrients available to plants.

  • Carbon Sequestration: Serves as a carbon sink, storing carbon.

  • Gas Production and Uptake: Participates in gas exchange processes.

  • Ecosystem Functions: Contributes to various ecosystem processes.

  • Habitat Provisioning: Offers living space for organisms.

  • Seed Dispersal and Germination: Aids in plant propagation.

Human System Functions

  • Pasture: Land for grazing livestock.

  • Crops: Cultivated plants for harvest.

  • Forest Crops: Timber and other forest resources.

  • Horticulture and Gardening: Cultivation of garden plants and vegetables.

  • Biofuels: Production of energy from organic materials.

  • Construction Materials: Used for fill and embankments.

  • Waste Disposal: Includes landfills and septic systems.

  • Pollutant Filtration and Absorption: Filters and absorbs contaminants.

Ecosystem Services Provided by Soil

  1. Provisioning Services:

    • Provides food, water, fiber, and raw materials.

  2. Regulating Services:

    • Regulates climate, water quality, and erosion.

  3. Supporting Services:

    • Nutrient cycling, soil formation, and habitats for biodiversity.

  4. Cultural Services:

    • Recreational and aesthetic benefits.

Soil Ecosystem Composition

Micro-organisms

  • Bacteria, Algae, Fungi, Protozoa, Nematodes: Key players in nutrient cycling and organic matter decomposition.

Macro-organisms

  • Fungi, Lichens, Mites, Nematodes, Earthworms, Ants, Beetles, Springtails, Spiders, Centipedes, Millipedes, Termites, Snails, Slugs: Contribute to soil health, structure, and nutrient cycling.

Functions and Roles of Soil

  • Physical Structure Change: Soil organisms change the soil’s physical characteristics.

  • Preconditioning: Break down organic material through various processes (mincing, mining, stripping).

  • Fragmentation and Sorting: Aid in soil structural organization.

  • Mineralization and Chemical Decomposition: Process of breaking down organic material.

  • Leaching: Movement of dissolved substances through soil.

  • Ingestion and Excretion: Soil organisms recycle nutrients and materials.

Productive Soil Data

  • 1 m² of productive soil contains:

    • > 10,000 Springtails

    • 100,000 Nematodes

    • 100,000 Mites

Organic Matter (OM) Replenishment

  1. Release of Energy: Provides energy for soil organisms.

  2. Release Chemical Elements: Essential nutrients for plants.

  3. Recycling and Further Growth: Supports ecosystem development.

Soil Productivity and Fertility

Key Characteristics of Fertile Soil

  • Texture: Mixed particle size promoting aeration and drainage.

  • Structure: Crumb or ped aggregates aiding root penetration.

  • Moisture Retention and Transmission: Facilitates water infiltration and availability.

  • Nutrient Retention: Holds essential nutrients for plants.

  • Organic Matter Richness: Supports microbial activity and nutrient cycling.

  • Neutral pH: Optimal conditions for plant growth.

Types of Soil Texture

  • Loam: Highly fertile texture that combines sand, silt, and clay.

Soil and Land Management (Agriculture, Forestry)

Optimizing Growing Conditions

  1. Physical Factors: Cultivation practices like ploughing and ridge creation.

  2. Chemical Factors: Management of nutrients (N, P, K, Ca) and pH levels.

  3. Biological Factors: Fertilisation, using biological control agents (biocides).

Cultivation Practices

  • Removal of vegetation cover.

  • Ploughing to loosen soil aggregates (peds).

  • Burying weeds/crop residues.

  • Creating soil ridges and fine ped structure.

Biological Cycles in Soil

  • Succession: The process of change in the species structure of an ecological community.

  • Competition: Organisms compete for resources within soil ecosystems.

  • Accumulation: Accumulating organic matter, nutrients, water, and biomass.

  • Decomposition: Breakdown of organic materials back into the soil.

  • Recycling and Regeneration: The continual process of nutrient cycling and soil health recovery.

Acceleration and Intensification of Soil Use

  • Natural Ecosystem vs. Agroecosystem:

    • Plant growth dynamics in natural environments compared to managed agricultural systems.

    • Nutrient cycling and leaching patterns.

Soil Classification

  • Definition: The categorisation of soils based on their characteristics and the environment where they are found.

  • Purpose: To organise soil knowledge, interpret characteristics, predict behavior for various land uses, and apply findings across geographical areas.

Classification Systems

  • Various systems exist worldwide, reflecting different soil-forming factors.

  • Irish System: 9 Soil Groups including:

    • Podzols

    • Brown Podzolics

    • Grey-brown Podzolics

    • Brown Earths

    • Gleys

    • Rendzinas

    • Lithosols

    • Blanket Peats

    • Basin Peats

Applications of Soil Mapping

  • Soil Scientists, Engineers, Farmers, Horticulturists: Use soil maps for practical applications and knowledge sharing.

Soil Formation and Human Impact

Factors Affecting Soil Formation

  • Climate, biota, topography, parent material, time, and human interference.

Human Interventions Affecting Soil

  • Activities Include:

    • Irrigation/drainage

    • Use of fertilizers, herbicides, pesticides

    • Ploughing reducing organic matter

    • Land alteration leading to erosion

    • Adding lime and topsoil for reclamation.

Consequences of Human Interference

  • Increased human and animal populations leading to:

    • Overgrazing

    • Increased cultivation

    • Deforestation

    • Farming on steep slopes.

Soil Degradation Processes

  • Erosion: Loss of topsoil and soil integrity.

  • Compaction: Increased soil density affecting root growth.

  • Soil Sealing: Reduced infiltration due to urbanisation.

  • Organic Matter Decline: Loss of essential nutrients affecting soil productivity.

  • Salinization: Accumulation of salts, detrimental to plant growth.

  • Landslides: Geophysical disasters due to weakened soil structures.

Reduction in Soil Quality and Viability

  • Detrimental impacts on soil health, resource availability, and overall quality.

Global Soil Degradation Statistics

  • 40% of soils are degraded globally, according to UN report.

Types of Soil Degradation

  1. Water:

    • Loss of topsoil through water erosion and mass movement (gullies).

  2. Wind:

    • Deflation leading to airborne soil particles and desertification.

  3. Chemical:

    • Pollution from biocides and salinisation due to irrigation practices.

  4. Physical:

    • Compaction, sealing, and waterlogging leading to various issues.

ON-SITE and OFF-SITE Effects of Degradation

  • Affects soil health, ecosystem functions, and economic aspects.

Hydrological Effects of Erosion

  • Reduced interception of water by foliage leads to increased erosive energy.

  • Decreased root strength and anchorage, promoting further erosion and instability.

Detailed Effects of Degradation on Water

  • Rapid wetting and subsequent soil degradation, resulting in reduced infiltration and erosion risk.

Historical Examples of Soil Degradation

  • Notable historical collapses:

    • Maya Civilization (900+ AD)

    • Roman Empire (500+ AD)

    • Colonial expansions in the 1700s.

    • Agricultural intensification post-WW2 impacting environmental sustainability.

The Dust Bowl (USA, 1930s)

  • Caused by poor land management practices, resulting in severe soil degradation and desertification.

  • Factors:

    • Overgrazing and removal of vegetation cover.

    • Technological advancements leading to displacement of topsoil and increased dust storms.

Specific Cases of Soil Damage

  • Mayo Landslide (2003): Events leading to significant alterations in local landscapes.

  • Derrybrien Galway Windfarm Landslide (2003): Illustrates risks associated with land use changes.

Learning Outcomes

  • Describe how human interference affects soil formation factors.

  • List the various forms of soil degradation and their implications.

  • Outline the effects of degradation on soil properties.

  • Recognize soil degradation as a key global environmental indicator.