Soil Flashcards
Soil is any solid earth material that can be removed without blasting.
This is a definition by?
Engineers
Soil is a solid earth material that has been altered by physical, chemical, and organic processes such that it can support rooted plant life.
This is a definition by?
Scientists
Soil involves the combination of _____, _____, ______, and ________ _________
rock, air, water, and organic material
Soil Component:
disintegrated and decomposed rock
Mineral matter (~45%)
Soil Component:
a complex solution containing many soluble nutrients
Water (~25%)
Soil Component:
source of oxygen and carbon dioxide
Air (~25%)
Soil Component:
decayed remains of plants and animals
Humus (Organic Matter) (~5%)
Physical and chemical breakdown of rocks and the first step in soil development
Weathering
Weathered rock is further modified by the activity of _____ _______
soil organisms
Controls of Soil Formation
- Parent Material
- Slope
- Time
- Climate
- Plants and Animals
[Parent Material]
Source of the mineral matter; can either be:
Bedrock (residual soil)
Unconsolidated sediment (transported soil)
[Slope]
Poorly developed soils
✓ Low moisture content
✓ Accelerated erosion
Steep Slope
[Slope]
Average Soils
✓ Some drainage
✓ Less erosion
Gentle Slope
[Slope]
Great Soils
✓ Good drainage
✓ Minimum erosion
✓ Sufficient infiltration of water
✓ Optimum terrain for soil development
Flat to undulating upland
The longer the soil has been forming, the thicker it becomes, and the less it resembles the parent material
Time
Most influential control of soil formation
Climate
Temperature and precipitation
Climate
Controls the type of plant and animal life
Climate
Decay → organic acid = ?
hastens weathering
Strong influence on the chemical and physical properties of the soil
Plants and Animals
Furnish organic matter
Plants and Animals
amount of organic matter present
Soil Fertility
vertical cross-section from the surface down to the parent material
Soil Profile
distinct layers formed in well-developed soils
Soil Horizons
A well-developed soil profile indicates that the environmental conditions have been relatively stable over an extended period and that the soil is _________.
mature
By contrast, some soils lack horizons. Such soils are called _________.
immature
Soil development has been going on only for a short time (e.g., steep slopes).
immature
[Soil Profile Development]
topmost layers, where organic matter decompose forming humus
O horizon
[Soil Profile Development]
where seeds are grown; rich in nutrients
A Horizon (topsoil)
[Soil Profile Development]
eluviation layer; contains dead soil, no nutrients
E Horizon
[Soil Profile Development]
hard and compact; only roots of old and big plants reach this; rich in mineral deposits and clay
B Horizon (subsoil)
[Soil Profile Development]
weathered parent material; no plant or organic matter
C Horizon (regolith)
[Soil Profile Development]
unweathered parent material
R Horizon (bedrock)
[Soil Particle Size]
if you can see individual grains
Sand
[Soil Particle Size]
if you can see the grains with a 10x hand lens
Silt
[Soil Particle Size]
if you cannot see the grains with such a hand lens
Clay
[Soil Texture]
gritty
Sand
[Soil Texture]
feels like baking flour
Silt
[Soil Texture]
cohesive
Clay
The Soil Texture Triangle is developed by?
US Dept. of Agriculture
good for plant life due to better moisture characteristics and nutrient storage capacity in comparison to soil consisting predominantly of clay or coarse sand
Loam Soil
[Soil Type]
highly leached soil rich in oxides of Fe and Al; hard, nutrient poor soil
Laterite
[Soil Type]
rich in calcite; less fertile, low amounts of organic matter.
Pedocal
[Soil Type]
rich in Al clays and Fe oxides; very fertile, dark brown or black soil
Pedalfer
Environmental Problems of Soils
- Soil Pollution
- Desertification
- Urbanization
- Use of Off-Road Vehicles
