Soils Flashcards
Soil
The uppermost layer of the earth’s crust or lithosphere
Pedology
Soil science, the study of soils
Four components of soil:
- Mineral fraction
- Organic matter
- Soil air
- Soil water
Soil Profile
- The vertical section of soil
- Differs in physical, chemical and organic composition and physical properties (texture, structure, colour)
O =
Organic horizons
Organic Horizons
Are derived from organic parent material and peat in wet ecosystems
L =
Leaf litter
F =
Fibric material
H =
Humus
Mineral Horizons:
- Ah
- Ae
- B
- C
Ah =
A horizon, rich in humus, dark, and nutrient rich
Ae =
A horizon, leached, grey and few nutrients
B =
Modified horizon and deposits from Ae
C =
Parent material and is essentially unaltered
CLORPT
Climate, organisms, relief, parent material, time
Climate:
The temperature and precipitation. It controls the physical and chemical weathering
Organisms:
Organic matter, biotic influences
Relief:
Topography, aspect and elevation
Parent Material:
Composition, structure, texture acidity and nutrients
Time:
Change, dynamic
Soil forming processes:
- Enrichment
- Removal
- Translocation
- Transformation
- Biological processes
- Human Impacts
Enrichment:
Material addition (mineral or organic deposition)
Removal
= Losses
- Surface erosion (materials removed from LFH or A horizons) and leaching (materials dissolved in water)
Translocation:
= Movement between horizons
- Eluviation
- Illuviation
Eluviation
- Is the downward transport of fine particles.
- Leaves sand and silt
- Results in Ae horizon
Illuviation
Is the accumulation of clay, humus and aluminum and iron oxides in B horizons
Transformation
- Mineral alteration
- Humification (decomposition of organics into humus)
Four main structure classes:
- Granular
- Platy
- Blocky
- Prismatic/columnar
Soil colour =
Composition and chemistry
Black soil =
Organic content
While/pale soil =
Silica and aluminium oxides
Red and yellow soils =
Iron oxides and minerals
Humus =
Very fine organic matter and a good source of nutrients
Air space depends on:
- Soil porosity
- Amount of soil water filling pores
Soil Water
- Is important for plants and soil organisms
- Held in soil pores depending on the amount of water present and the size of pores
Types of soil water:
- Gravitational water
- Capillary water
Gravitational water
Water removed by gravity when soil is saturated
Capillary water
Water that resists gravity by clinging to soil particles via capillary tension
If we add equal amounts of water to equal volumes of a
fine versus coarse textured soil, in which soil will a plant wilt first?
The plant will wilt first in the fine textured soil. The fine textured soil has large surface area and
small pores, and water binds to the surface
with strong capillary tension.
The water is more difficult for plants to extract.
Fine textured soils:
Have…
- High storage capacity
- High capillary tension
- High wilting point
- Low water availability
Coarse textures soils:
Have…
- Low storage capacity
- Low capillary tension
- High water drainage
- Low water availability
Which texture class has the greatest available water capacity?
Loam.
