Soil formation 2

BY4012

Soil

Top layer of the Earth’s surface composed of mineral material, organic matter, organisms, air, and water

Soil system

A complex and dynamic system with chemical, physical, and biological properties that vary over space and time

Soil (SSSA definition)

Unconsolidated mineral or organic matter at the Earth’s surface formed by climate, organisms, relief, parent material, and time

Soil profile

Vertical section of soil showing different layers (horizons)

Soil horizon

A distinct layer in the soil profile with specific properties

Purpose of studying soil profiles

To understand soil functions, formation, and land-use potential

Soil components

Mineral particles, organic matter, water, air, and living organisms

Ideal soil

Balanced proportions of solids, water, and air for plant growth

Soil forming factors

Climate, organisms, relief, parent material, time, and anthropogenic activity

Parent material

Original mineral or organic material from which soil develops

Types of parent material

Igneous, sedimentary, metamorphic rocks, and unconsolidated materials

Transported parent material

Soil material moved by ice, water, wind, or gravity

Effect of parent material

Influences soil texture, chemistry, and weathering rate

Relief

Shape of the land including slope, elevation, and landscape position

Effect of relief on soils

Controls drainage, erosion, soil depth, and fertility

Valley soils

Deep and fertile due to deposition and moisture availability

Slope soils

Shallow and often leached due to erosion

Soil organisms

Plants, animals, and microorganisms living in and on soil

Bioturbation

Mixing of soil by living organisms

Role of vegetation

Contributes organic matter and influences horizon development

Role of earthworms

Enhance soil mixing and fertility through burrowing and digestion

Time as a soil factor

Duration over which soil-forming processes operate

Young soils

Less weathered with fewer horizons

Old soils

More acidic, clay-rich, iron-rich, and deeply weathered

Determining soil age

C-14 dating, volcanic ash layers, and artifacts

Climate

Major driver of soil formation through temperature and precipitation

Precipitation effect

Promotes leaching and movement of materials in soil

Temperature effect

Controls rate of chemical and biological reactions

Climate zones and soils

Different climates produce distinct soil types

Anthropogenic activity

Human actions that alter soil formation

Land-use impacts

Deforestation, cultivation, erosion, and compaction

Soil reclamation

Drainage of wetlands and land restoration

Atmospheric deposition

Acid rain and nutrient inputs affecting soils

Climate change impact

Increased temperature and altered rainfall patterns

Ombrotrophic peat soils

Rain-fed peat soils common in Ireland

Minerotrophic peat soils

Peat soils influenced by groundwater

Rendzina soils

Shallow, limestone-derived soils

Lithosols

Very shallow soils over bedrock

Alluvial soils

Soils formed from river-deposited materials

Groundwater gley

Poorly drained soils influenced by groundwater

Surface water gley

Soils affected by surface waterlogging

Podzol

Acidic, leached soils under forest or heath

Brown podzolic soils

Moderately leached soils with mixed properties

Luvisol

Clay-enriched subsoil with relatively high fertility

Brown Earth soils

Well-drained, fertile soils common in Ireland

Soil variability

Soils differ across sites, regions, and countries

Reason for soil diversity

Variation in intensity of soil-forming factors