1.1 Postlab Factors of Soil Formation
- Soils formed from different parent materials (residual vs transported) show varying degrees of development.
- Residual parent material: Formed in place, resulting in:
- Lower degree of horizon formation due to lack of environmental influences.
- Fewer distinct horizons (A, E, B).
- Transported parent material: Influenced by environmental factors (wind, water, ice, gravity) leading to:
- Higher degree of development evident from a greater number of horizons observed.
- Soils from regions with varying rainfall intensities were studied.
- Higher rainfall intensity results in:
- Deeper horizons with a characteristic "k" layer (indicative of leaching).
- Significant leaching processes that affect mineral content and soil composition.
- Comparison of soils formed under grassland vs forest vegetation.
- Grassland soils:
- Thicker, dark surface layer due to abundant root masses.
- Contributes substantial organic matter (OM) upon decay, resulting in darker colors.
- Forest soils:
- Dark color attributed to humus but generally less OM contribution than grasslands.
- Various landscape positions of soils examined.
- Waterlogged soils (gleyed):
- Characterized by the presence of the letter "g" indicating poor drainage.
- Formation leads to anaerobic conditions causing the reduction of iron (Fe).
- Appearance: Typically gray color due to reduced Fe.
- Mottled soils:
- Presence of spots or blotches of color (grey/orange) due to wetness conditions.
- Comparison of soil profiles of varying ages.
- Oxisols and Ultisols:
- Red/rust color indicative of high oxidation states of iron.
- Both types are common in humid tropical areas and are characterized by:
- High acidity and low fertility.
- Oxisols are the most weathered soils, while Ultisols are strongly leached.
- Younger soils:
- Generally exhibit higher fertility, as older soils lose nutrients through leaching and weathering.
- Inceptisols:
- Newly formed soils showing minimal horizon development.
- Alfisols:
- Forest soils characterized by higher fertility and better development over time.