Introduction to Soil Science and Pedogenesis

B Horizon

Subsurface layer enriched with organic matter and clay.

L Horizon

Accumulation of recognizable organic matter structures.

Chroma

Purity or intensity

Pedogenesis

Process of soil development over time.

Weathering

Breakdown of rocks and minerals at surface.

Physical Weathering

Mechanical breakdown of rocks without chemical change.

Chemical Weathering

Chemical reactions that decompose rocks and minerals.

Organic Horizons

Soil layers with over 30% organic matter.

O Horizon

Developed from mosses and woody materials.

Of Horizon

Fibric materials identifiable by botanical origin.

Om Horizon

Mesic material, intermediate decomposition stage.

Oh Horizon

Humic material, advanced decomposition stage.

Mineral Horizons

Soil layers with 30% or less organic matter.

A Horizon

Surface layer, zone of leaching and organic accumulation.

C Horizon

Layer minimally affected by soil-forming processes.

Soil Color

Indicates origin and moisture level of horizons.

Mottles

Spots or blotches in dominant soil color.

Gleying

Distinctive gray colors due to water saturation.

Primary Particles

Soil particles smaller than 2 mm in diameter.

Coarse Fragments

Soil particles larger than 2 mm in diameter.

Soil Texture

Composition of sand, silt, and clay in soil.

Textural Triangle

Graphical representation of soil texture classification.

F Horizon

Accumulation of partly decomposed organic matter.

H Horizon

Accumulation of fully decomposed organic matter.

Stages of Pedogensis

1. Weathering
2. Addition of organic matter and formation of clay.
3. Mixing, translocation and transformation of matter.
4. Removal by leaching or erosion.

Component's of physical weathering

1. Liquid movement
2. Wind blowing fine particles (sandpaper)
3. Ice gouging or grinding (glaciation)

Hue

Colour

Value

Lightness