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Soil Resources
Soil Erosion, Degradation, and
Conservation
Soils
• What is soil and why is it important?
– Soil is a slowly renewed resource that provides
most of the nutrients needed for plant growth and
also helps purify water.
– Soil is a thin covering over most land that is a
complex mixture of eroded rock, mineral
nutrients, decaying organic matter, water, air, and
billions of living organisms, most of them
microscopic decomposers
Soil is Renewable – Natural Resource
• Soil is renewed very slowly!!
– 1 cm can be renewed in approximately 15-hundreds
of years!!!
– It provides most of the nutrients needed for plant
growth. We cannot waste it and deplete its
nutritional value.
– It is also Earth’s primary filter that cleanses water as
it passes through.
• Thank the soil the next time you have a glass of water!
Soil Profile
• Mature soils (developed over a
long time) are arranged into soil
horizons each with a distinct
texture and composition.
• The top two layers are held in
place by the roots of most
plants and most of the soil’s
organic matter is concentrated
here:
– Filled with bacteria, fungi,
earthworms, and small insects
that interact in complex food
webs.
Soil Profile
• Surface litter layer (top) consists
of freshly fallen undecomposed
or partially decomposed leaves,
twigs, crop wastes, animal
wastes, fungi, and other organic
materials.
– It is usually brown or black in color.
• Topsoil layer (Second): is a porous
mixture of partially decomposed
organic matter called humus and
some inorganic mineral particles.
– It is darker and more loose than
deeper layers.
– It is good for holding water and
nutrients to be taken up by plants
Bottom Layers…
• The subsoil and parent
material contain most of the
soils inorganic matter.
– Broken down rock: sand, clay,
silt, and gravel.
– The B horizon is above the C
horizon which lays on top of the
bedrock
• The best soil to use for
growing crops are ones that
contain brown or black
topsoils.
Soil Erosion
• Soil erosion is the movement
of soil components, mainly
topsoil, from one place to
another.
• The Big Three:
– Water
– Wind
– People
• Although most people in
developed countries obtain
food from grocery stores or
restaurants, we need to
remember that all food comes
from the soil.
Land Degradation
• Occurs when natural or human induced processes
decrease the chances of any future use of the land to
support crops, livestock, or wild species.
• The two main causes of this are flowing water and wind
– water being the biggest problem.
Global Soil Erosion
• United Nations and the World Resource
Institute estimate that 38% of the world’s
cropland is being depleted before being
renewed…
• Economy: $400 Billion is lost due to damage to
agricultural lands, waterways, infrastructure,
and human health.
Canada?
• Looks different across the country.
• We are losing soil more than it is being
replaced.
• Depending on where you are at it can be due
to wind (in the Prairies) or water (in the
Maritimes).
• Urban development in areas such as PEI is
constantly using valuable land to grow new
subdivisions
So why are humans a problem?
• We mess with the natural ecosystem…
– We introduce farming, logging, construction,
overgrazing of livestock, off-road vehicle use, and
deliberately burn vegetation.
– All of these activities, destroy plant cover.
– The topsoil (which we rely on for the growth of
crops) is held in place by the roots of the plants
that anchor it in place.
– In natural ecosystems, soil is usually not lost before
it forms because of the plants anchoring it in place.
Major Harmful Effects
1. Loss of soil fertility
– Cannot grow crops.
2. Eroded soil forms as
sediments in nearby
waters
– polluting the water
– kill fish and shellfish
– clog irrigation ditches,
boat channels, reservoirs,
and lakes.
Soil Conservation
• Soil conservation is when we try to reduce
erosion as much as possible and try to
increase the fertility.
– Conservation-tillage farming: disturbs the soil as
little as possible
• Advantages: reduces erosion, saves fuel, cuts costs,
holds more soil water, reduces soil compaction, allows
several crops per season, does not reduce crop yields,
and reduces CO2 release from soil.
• Disadvantages: can increase herbicide use, leaves stalks
that can have fungal diseases increasing pesticide use,
and requires an investment in expensive equipment.
Soil Conservation on PEI
• We are subjected to wind and water erosion based on our
location.
• PEI lost half of it’s topsoil when a severe rain storm hit in
2003 (Hurricane Juan) – this created changes.
• Farmers started to change their farming practices through a
variety of ways
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Minimum or reduced tillage
Crops are planted in strips
Cover crops
shelter belts to prevent wind erosion
Crop rotation (five year)
Terraces on steep land
Vegetated buffer zones to prevent water washing into
waterways.
Activity: Soil Erosion and Conservation
Worksheet
• Portfolio work…