PART 2-LESSON 1Soil as a resource that requires careful management

SOIL EROSION AND CONTROL Because most of Australia’s soils are nutrient

deficient, good soils are valuable to the country. Therefore soil management is very important to ensure these soils for the future.

SOIL EROSION AND CONTROL The main problem

faced by management bodies is erosion. The erosion of soil is a global problem. It’s been estimated that 1/3 of the worlds workable topsoil has been lost in the last 30 years.

SOIL EROSION AND CONTROL If the soils which we depend upon to produce

food are lost, starvation is eminent. As the worlds population continues to increase the demand for food will also increase.

If we don’t look after our soil what might the result be?

SOIL EROSION AND CONTROL Soil erosion is the removal

of surface layers or top soil from an area. Why is this a problem? The top layers are those that contain nutrient rich soils which are vital to plant growth.

What causes soil erosion?

SOIL EROSION AND CONTROL Wind and water are the major contributors to

soil erosion. Erosion is worst where soil has become exposed. Areas naturally susceptible to soil erosion are arid places or places with steep slopes.

Does man create areas which may be susceptible to soil erosion?

WIND One type of soil erosion that we are all

familiar with occurs during a dust storm. High winds lift the top layers of soil from the country and carry them as a cloud over large distances.

WIND These dust clouds are able to form if an area

is dry and the moisture that binds the soil particles together has evaporated. If the particles are not bound together it makes them much easier by wind.

WIND A lack of vegetation also contributes to dust

storms. Plants hold soil together with their roots and also act as a wind break.

WIND Dust storms have been naturally happening

for a long time. For example, dust from the Central Coast have been found in sediments on the bottom of the Tasman Sea which date back 18000 years.

WIND Human activity can also contribute to dust

storms. Today’s agricultural practices frequently leave large areas of bare ploughed soil. Once the soil has been loosened and dried out there is nothing to hold it down.

WIND Clearing of land for

paddocks also contributes to soil erosion. Removing trees and native vegetation exposes the land to wind.

WIND Overgrazing paddocks is another way soil

can be exposed to wind.

WIND All of these human activities can be avoided

and managed with appropriate practices. For example; paddocks can be planted with perennial crops to

reduce the amount of time soil is left bare Stock can be rotated to give paddocks a chance

to regenerate before the soil is bare Windbreaks can be planted Ploughing can be minimised

WIND There is evidence for soil erosion that

predominates human existence found in geological records which proves that soil erosion is a naturally occurring event.

Should we worry about the human impact? Why/why not?

HOMEWORK

Read pages 113-115 HSC Spotlight TextUpdate Electronic vocabulary Activity 3.4 Weathering, Erosion and Soil pg 116 HSC Spotlight Text

PART 2-LESSON 2Soil as a resource that requires careful management

WATER Last lesson we discussed how wind is a

means for erosion. Today we are going to discuss another powerful erosion agent: Water.

WATER If we took a trip to the river we could see

how water transports sediments. The sediments dissolved in the river water are what give it it’s colour and lack of transparency.

WATER Water has the potential to carry much larger

sediments than wind. It can also leave more visible examples of erosion such as the Grand Canon.

WATER Water naturally

carries away sediments which contain nutrients from soil. Natural rainfall has played a major role in the erosion of land.

WATER We live in an area that is largely affected by

water erosion. Early settlers overgrazed pastures of natural vegetation and cleared trees for paddocks and building.

WATER These bare surfaces led the soil to

deteriorate rapidly. The soil soon lost it’s ability to absorb water. What effect do you think this would have had?

WATER If the soil lost it’s ability to absorb water,

which means water no longer seeped into the ground, the only alternate path was to become run-off and carry the soil away with it.

WATER This process removes soil and valuable

nutrients and deposits them into river systems. The result is often deep gullies that are hard to re-work and very unstable.

WATER These early

practices has left hectares of useless land. Today most farmers are more careful about stripping fields of vegetation.

WATER As with wind erosion, all of these human

activities can be avoided and managed with appropriate practices. For example; paddocks can be planted with perennial crops to

reduce the amount of time soil is left bare Stock can be rotated to give paddocks a chance

to regenerate before the soil is bare Digging drainage canals to provide a pathway for

large amounts of water in heavy rain.

ACTIVITY Science Skills pg 117 HSC Spotlight Text

HOMEWORK

Complete ‘To Think About’ pg 117-118 HSC Spotlight Text

PART 2-LESSON 3Soil as a resource that requires careful management

SOIL AND URBAN DEVELOPMENT Agriculture is not

the only human activity that affects the rate of soil erosion. Urban development also plays a role.

SOIL AND URBAN DEVELOPMENT Development disrupts waters natural

pathway. For example, soil that is covered by impermeable materials such as concrete, no longer absorb water. This water that would have naturally been absorbed has been rerouted to other areas which may not be capable of handling the excess water and result in high rates of soil erosion.

SOIL COMPACTION LAB PREP Read and discuss the lab in preparation for

next lesson.

HOMEWORK

Complete DOT Point 2.1 page 57Finish outstanding homework