Soil

What is Soil?

• Definition: Natural body of minerals, water, air, organic material

• Distinguishable from parent material, capable of supporting life

• Differentiation: Soil vs. Dirt, termed as "skin of the earth"

• Importance of Soil: Contains diverse organisms, more than human population

Soil Composition and Horizons

• Essential Elements for Plant Growth:

  • 17 out of ~90 natural elements necessary

  • C, O, H as non-mineral elements

  • Some beneficial but non-essential elements known

• Structure of Soil Profile:

  • Composed of horizons, generally parallel to surface

  • Classification Systems: Master horizons indicated by capital letters (A, B, C for minerals; O, L, F, H for organics)

Parent Material and Weathering

• Parent Material (P): Influences physical/chemical traits of soil, may be mineral or organic

• Weathering processes (chemical, biological, physical) alter parent material

• Horizon Characteristics:

  • A (topsoil): Mainly mineral + organic matter

  • B (subsoil): Contains leached materials

  • C (least weathered)

Soil Formation Factors

• Five Factors: Climate, Organisms, Relief, Parent Material, Time (Cl.O.R.P.T)

• Soil Formation Process:

  • Inheritance from parent material

  • Climate impacts drainage and weathering depth

  • Organisms contribute to organic matter and promote weathering

  • Topography affects moisture, drainage, temperature

  • Time impacts soil development; younger soils present in some regions

Canadian Soil Orders

• Examples: Chernozem, Podzol, Luvisol, Solonetz

• Canadian vs. US classification systems

  • 10 orders in Canada, 12 in US, 32 in WRB

Upcoming Activities

• Next lecture: Soil classification

• Outdoor lab: Site digging for soil pit assessment scheduled next week

• Prepare accordingly for weather conditions