soil resources soil erosion, degradation, and conservation

Soil ResourcesSoil 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– 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…