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EESA01H3 (141)
Lecture

Week 7

6 Pages
87 Views

Department
Environmental Science
Course Code
EESA01H3
Professor
Carl Mitchell

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Lecture 6
Soil as a system
Soil: disintegrated rock; organic matter+water+gases+nutrients+micro-organisms
½ mineral matter with varying proportions of organic matter
has much influence on surrounding ecosystems
leaching/soil creation: occurs in warmer/wetter climates- faster chemical
reactions and heat
Definitions
Parent material: base geological material in a particular location can include lava,
volcanic ash, rock sediment deposits by glaciers and rivers
Bedrock: continuous mass of solid rock that makes up the earths crust
Weathering: physical/chemical/biological pressure that breaks down rocks and
minerals, turning large particles into smaller particles
Physical weathering/mechanical: breaks down rocks without trigerring chemical
change in parent material
Chemical weathering: when water or other substances chemically react with
parent material
Biological weathering: when living things break down parent material by physical
or chemical means
Erosion: the movement of soil from one area to another
Humus: a dark spongey crumbly mass of material made up of complex organic
compounds
Peat: soils that are dominated by partially decayed compressed organic matter
(characteristic of northern climates)
**Decomposition, deposition, and accumulation of organic matter can contribute
to soil formation
Soil Profile- horizons
O horizon: (organic) upper most layer consisting mostly of organic matter such as
decomposing leaves, animal wastes and branches
A: consisting of inorganic mineral components, with organic matter and humus
from above
O and A are home to countless organisms
B/subsoil: contains minerals and organic matter that move down from A horizon
and accumulate (less organic materials)
C: below B, consists of weathered parent material, unaltered by or slightly altered
by process of soil formation
www.notesolution.com
R: rock/ parent material (limestone: more dissolvable, granite: not dissolvable)
W: water
Soil Characterization
- colour: indicates composition and fertility- red (PEI)= lots of iron; - black/dark
brown=rich in organic material; pale grey/white=low organic material
- texture: determined by size of particles- a) clay, b) silt, c) sand
- loam: soil with relatively even mixture of the 3 particle sizes- best for growing
stuff
- porosity: measure of relative volume of spaces within material
**large particle soil makes it easier for water to pass through, requiring more
frequent irrigation
-structure: measure of organization/clumpiness of soil- clumps that are too large
discourage plant growth
- chemical pH
Soil Chemistry: Cation exchange
- prinicipal means by which plants gain nutrients
- plant roots donate hydrogen ions to soill in exchange for nutrient ions (positive)
- more negatively charged surfaces on soil means more positively charged ions
can be held
- Cation Exchange Capacity (CEC) expresses a soils ability to hold onto cations
(not to be leached out) determines fertility parameter
- sandy loam with neutral pH is best soil for soils
Food
- 38% of land use is for agriculture
- soils continue to degrade as agricultural needs increase due to increase in
population
- extensification: expand (not sustainable)
- intensify: increase productivity in given unit of land
- soil degradation: damage/loss of soil by forest removal, cropland agriculture,
overgrazing livestock, and industrial contamination
Agriculture
Fertile crescent: was in middle east (rye, peas, lentils, etc.
Traditional agriculture: performed by human and animal muscle
Industrialized agriculture: 25% of the cropland
Swidden: when a farmer cultivates a plot of land for a few years, then moves
goes on and on and on
www.notesolution.com

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Description
Lecture 6 Soil as a system Soil: disintegrated rock; organic matter+water+gases+nutrients+micro-organisms mineral matter with varying proportions of organic matter has much influence on surrounding ecosystems leachingsoil creation: occurs in warmerwetter climates- faster chemical reactions and heat Definitions Parent material: base geological material in a particular location can include lava, volcanic ash, rock sediment deposits by glaciers and rivers Bedrock: continuous mass of solid rock that makes up the earths crust Weathering: physicalchemicalbiological pressure that breaks down rocks and minerals, turning large particles into smaller particles Physical weatheringmechanical: breaks down rocks without trigerring chemical change in parent material Chemical weathering: when water or other substances chemically react with parent material Biological weathering: when living things break down parent material by physical or chemical means Erosion: the movement of soil from one area to another Humus: a dark spongey crumbly mass of material made up of complex organic compounds Peat: soils that are dominated by partially decayed compressed organic matter (characteristic of northern climates) **Decomposition, deposition, and accumulation of organic matter can contribute to soil formation Soil Profile- horizons O horizon: (organic) upper most layer consisting mostly of organic matter such as decomposing leaves, animal wastes and branches A: consisting of inorganic mineral components, with organic matter and humus from above O and A are home to countless organisms Bsubsoil: contains minerals and organic matter that move down from A horizon and accumulate (less organic materials) C: below B, consists of weathered parent material, unaltered by or slightly altered by process of soil formation www.notesolution.com
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