GEG 1301 Lecture Notes - Lecture 14: Pedogenesis, Hygroscopy, Tilth

• School: University of Ottawa
• Department: Geography
• Course: GEG 1301
• Professor: Denis Lacelle

Document Summary

Soil is a multi-phase, open system that contains organic matter. Minerals (~ 45%), weathered rock fragments + secondary minerals (iron oxides, carbonates and clay) Air (20-30%), 79-80% nitrogen, 15-20% oxygen and 0. 25-5% co2. Water (20-30%), surface, gravitational, capillary and hygroscopic water. Organic material (~5%), humus, accumulation and decay of leaves, stems, roots, plants, and dead bodies of animals due to micro-organisms. O-horizon contains >20-30% of the organic matter, and good at retaining water and nutrients. Regolith: physically or chemically weathered rock overlying the bedrock (no o horizon) Depth/development of soil is determined by its history (time to develop), climate and biological activity. Climate: warm temps. and high moisture accelerate the chemical reactions in soil, leading to the development of thick soils. Moisture is determined by precip. and evapotranspiration. Topography: north- vs. south-facing slopes, amount of moisture received (wind- vs. lee-ward slope), runoff and infiltration. Soil profile is not consistent along a slope (thicker soil at bottom)