Download SOIL FORMATION FACTORS

Lecture 6
SOIL FORMATION
FACTORS
Soil Forming Factors
1. Parent Materials
2. Climate
3. Vegetation
4. Topography
5. Time
PARENT MATERIAL
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From rocks or materials brought from sea
clay and river clay.
Its influence soil formation through:
Weathering capacity ; depend on types of
mineral in the parent materials
Nutrient content influence a lot of alive
plant.
PARENT MATERIAL
Definition: The primary material from
which the soil is formed.
- bedrock,
- organic material,
- alluvial: deposit from water,
wind, glaciers, volcanoes,
or material moving down
a slope
Organic soil
Mineral soil
Colluvial material
Aluvium
Sedimentary rock.
Sandstone, } quartz
limestone, } carbonate
Shale,
} clay
-Limestones: fast weathering, but commonly
make nutrient-poor soils
The type of soil that forms
depends on the type of rocks
available, the minerals in the
rocks, and how minerals
react to temperature,
pressure, and erosive forces
Igneous rocks
- Mafic vs. felsic: mafic rocks have minerals
that weather more readily than those in
felsic rocks
- Plutonic vs. Volcanic: most plutonic rocks
are crystalline and competent where
volcanic rocks are more porous and
fractured. Thus volcanic rocks allow water
to enter into the pores and fractures and
contribute to weathering more rapidly.
Mendapan marin
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Size of particle for parent materials (E.g.
:sandstone = sand, conglomerat = rocks
and shale = clay )
Influence of parent materials depend on
time. Hard effect (dominant) for young
soil (E.g. Entisol and Inceptisol order).
For older soil, factors of climate and
organism is more important. (E.g. Ultisol
and Oxisol order).
Main parent materials in Malaysia :
granite, limestone, basalt, clay (river
and sea) and sandstone.
Temperature,
Precipitation
Temperature:
a. hot temperatures contribute to rapid
chemical weathering,
b. cool temperatures slow things down,
c. freezing temperatures keep water
from making any contribution.
The hotter and more humid a climate,
the faster and more completely big
rocks are broken into smaller rocks,
then into pebbles, then into tiny
particles that make up the loose stuff
we call soil.
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temperature and rain determine type
of plants, animals and microb
activities.
Examples :
Arid temperature – spot plant (grass
type) and shrub.
Humid temperature – tropical forest
Rain erode soil at the slope area.
Precipitation (rain, snow,
humidity)
Water is key to virtually all the chemical
weathering processes. Deserts weather
mechanically, with very little chemical
weathering
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Rain that absorbed into soil transfer
clay, humus and dissolve materials from
upper layer to down layer through
leaching process to cause horizon
formation.
Arid temperature formed shallow soil,
low organic matter content and
accumulation of salt at the above
horizon. Humid temperature formed
inmost soil, high organic matter content
and well-decomposed and acidic soil
(pH< 5.5)
Stratigrafi/lapisan
Organisms:
- All plants (vegetation)
- animals living in or on the
soil (including micro-organisms)
- humans
•
Plants and alive animals play important
part in soil formation
Plant
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Type of plants influence formation of soil
horizon.
Grass – A horizon (thick) , good structure and
dark in color.
Desert Soil
Animals living in the soil affect
a. decomposition of waste
materials
b. how soil materials will be moved around in
the soil profile.
c. On the soil surface remains of dead plants
and animals are worked by
microorganisms and eventually become
organic matter-enrich the soil.
termite
The location of a soil on a landscape can affect
how the climatic processes impact it. Soils at the
bottom of a hill will get more water than soils on
the slopes, and soils on the slopes that directly
face the sun will be drier than soils on slopes that
do not.
Also, mineral accumulations, plant nutrients, type
of vegetation, vegetation growth, erosion, and
water drainage are dependent on topographic
relief.
All of the above factors assert
themselves over time, often hundreds
or thousands of years. Soil profiles
continually change from weakly
developed to well developed over time
ERA
PERIOD
QUARTERNARY
EPOCH
MULA SELANG (juta tahun
sebelum sekarang)
Holocene
0.01
Pleistocene
2.00
Pliocene
CENOZOIC
Miocene
TERTIARY
Oligocene
Eocene
Paleocene
MESOZOIC
CRETACEOUS
135.00
JURASSIC
192.00
TRIASSIC
230.00
PERMIAN
290.00
PENNSYLVANIAN
PALEOZOIC
65.00
Carboniferous
320.00
MISSISSIPIAN
350.00
DEVONIAN
410.00
SILURIAN
435.00
ORDOVICIAN
485.00
CAMBRIAN
560.00
Soils change over time as
they weather. Weathering
in the soil takes place over
thousands of years. Just
like people, soils can be
mature or youthful. Each
has its particular
characteristics based not so
much on their age as on
their level of development.
Slightly developed
Highly developed
Differences in soil
forming factors from
one location to another
influence the process
of soil formation