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5.1 INTRODUCTION TO SOIL SYSTEM - Coggle Diagram
5.1 INTRODUCTION TO SOIL SYSTEM
SOIL PROFILE
how soil interacts with the:
HYDROSPHERE: The water cycle moves through the soil by infiltration and water may evaporate from the surface.
ATMOSPHERE: The atmosphere may contain particulate matter that is deposited on the soils and particles may blow up into the atmosphere.
LITOSPHERE: Rocks in the lithosphere weather to form soils, and soils at depth and pressure may form rocks.
BIOSPHERE: Plants in the biosphere may extract nutrients from the soils and dead plants may end up forming parts of the soil.
O: organic horizon, helps prevent erosion, hold moisture
A: dark colored, stained by down washed humus. layer where seeds germinate and plant root grows. most biological activity occurs here.
E: made up by sand and silt, lighter color due to removal of clay and calcium by water
B: possible iron accumulation, brighter color due to deposition of iron and aluminium, little humus, plat root penetrate through this layer.
C: mineral layer, show little or no sign of soil formation
SOIL SYSTEM
primary function of soil:
medium for plant growth,
water storage,
habitat for organisms,
modifies the atmosphere
25% air,
45% mineral particles,
25% water,
organic matter 5% (organism 10%, roots 10%, humus 80%)
open system
linked to other environmental systems
linked to the lithosphere system through weathering and erosion
central role in many biogeochemical cycles
provides a short term store for chemical elements
main interface between abiotic & biotic processes within ecosystems
SOIL FORMING PROCESS
FACTORS AFFECTING SOIL CHARACTERISTICS
climate
organisms
relief
parent material
time
gains and losses of material to and from the profile (transfer)
movement of water between horizon (translocation, leaching)
chemical transformations within each horizon (decomposition, weathering & nutrient cycling)
BIOLOGICAL MIXING
burrowing animals like earth worms, move soil materials within the profile
it create passageways through which air and water can travel promoting soil development
LEACHING
downward loss of nutrients through soil layers (horizon). Nutrients carried by water as it percolates through the soil matrix.
water percolates downward faster than plants can absorb it = net loss of nutrients
soil texture influence leaching rate
TRANSFORMATION
weathering
decomposition
nutrient cycling
SOIL STRUCTURE AND PROPERTIES
BENEFITS OF SOIL TO SUPPORT PLANT GROWTH
anchorage for roots
supply of water
supply for oxygen
supply of mineral nutrients
protection against adverse changes of temperature and pH
PHYSICAL CONDITIONS THAT RESTRICT ROOT GROWTH
mechanical barriers
absence of cracks
shortage of oxygen due to waterlogging
dryness
temperature that are too high or too low
CHEMICAL CONDITIONS THAT RESTRICT ROOT GROWTH
high aluminium concentration
low nutrient supply
trace metals or salinity associated with insecticide or herbicide
CLAY SOIL
>
surface area
>
potential for exchange nutrients
but become waterlogged
cold and heavy
<
primary productivity due to poor aeration and water infiltration
SANDY SOIL
>
drain
driest & free draining
<
primary productivity
LOAM SOIL
optimum combination of sand, silt & sand
easily workable
drains well
retain moisture and nutrient
>
plant productivity
