Soil Profile and Properties

These include soil profile, soil depth, soil color, soil texture, porosity, and structure.

A vertical section from the surface to the parent rock, characterized by distinct layers, usually differing in texture and color.

The ideal soil profile has three horizons: A, B, and C horizons.

Horizon A

1. The topmost layer, which may include organic matter to form humus.
2. Varies in color (e.g., dark, grey).
3. Known as the zone of eluviation, from which materials are washed downward.

Horizon B

1. Known as the zone of accumulation.
2. Materials washed from Horizon A are deposited or accumulated here.

Horizon C

The partially weathered parent rock from which the soil develops.

R-Horizon

The fresh (unweathered) parent rock.

D-Horizon (Bedrock)

The unweathered parent rock, the source of the inorganic content of the soil.

1. Soil depth varies from place to place depending on maturity.
2. Maturity is influenced by the nature of the rock and the duration of soil-forming processes.
3. Deep soil is important for agricultural activities, while shallow soil is not suitable for cultivation.

Soil color is influenced by the materials and mineral composition from which the soil is derived, as well as the organic matter content.

Soil color can be classified as:

• Dark: black, grey, dark brown, cinnamon
• Bright: yellow, orange, red, reddish brown, yellow brown
• Light: white, whitish grey

1. Refers to the degree of coarseness of soil, specifically the soil mineral particles.
2. Can be described in terms of particle size, caliber, or mechanical composition.

Soil can be classified as:

• Coarse sand: 2 to 0.2mm
• Fine sand
• Silt: 0.02mm
• Clay: less than 0.002mm
• Loam soil: a mixture of sand, clay, and silt

Importance of Soil Texture

1. Influences soil porosity, permeability, structure, and retention capacity.
2. Affects plant growth and root penetration.
3. Impacts cultivation during agricultural activities.
4. Influences resistance against soil erosion.
5. Affects soil fertility.

1. Refers to the total volume of pores or empty spaces between soil particles.
2. Soil porosity is influenced by soil texture, organic matter, soil structure, and undisturbed soil aggregates (peds).

1. Refers to the arrangement of soil particles into aggregate compounds, which form peds of different shapes and sizes.
2. Soil is described as structureless if aggregation is absent (e.g., loose sand).

Importance of Soil Structure

• Determines water retention capacity and aeration.
• Acts as an indicator of soil fertility or suitability for agriculture, settlement, and construction.
• Facilitates the activities of microorganisms.
• Influences cultivation processes, plant growth, root penetration, and water retention.

1. Soil temperature varies based on climatic conditions.
2. In polar latitudes, soils are cold due to low insolation.
3. In tropical areas, soils are warm due to high insolation.

Importance of Soil Temperature

• Controls biochemical and chemical processes, including decomposition of organic matter and plant growth.
• Determines the existence of microorganisms in certain areas.
• Affects the moisture content of soil; high evaporation reduces moisture, leading to dry soils.

These include soil reaction (pH), cation exchange, and leaching.

Soil Reaction (Soil pH)

1. Describes the degree of acidity and alkalinity in the soil.
2. Expressed in pH value, which indicates hydrogen ions concentration.

Importance of Soil pH

1. Helps determine crop selection and agricultural distribution.
2. Affects plant growth; high acidity can hinder growth due to increased leaching and poor soil structure.

Leaching

1. The process in which nutrients are washed down from the topsoil in solution.
2. Leaching is more effective in wet conditions (e.g., equatorial areas) and less effective in dry areas, where bases accumulate in the topsoil through calcification.

Cation Exchange

1. Refers to the process in which cations (e.g., Calcium, Magnesium, Potassium, Sodium) replace hydrogen ions in the soil.
2. Takes place between soil particles, the soil solution, and plant roots.