Part 2-Lesson 1

1. Part 2-Lesson 1 Soil as a resource that requires careful management

2. 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.

3. 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.

4. 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?

5. 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?

6. 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?

7. 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.

8. 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.

9. Wind • A lack of vegetation also contributes to dust storms. Plants hold soil together with their roots and also act as a wind break.

10. 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.

11. 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.

12. Wind • Clearing of land for paddocks also contributes to soil erosion. Removing trees and native vegetation exposes the land to wind.

13. Wind • Overgrazing paddocks is another way soil can be exposed to wind.

14. 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

15. 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?

16. Homework Read pages 113-115 HSC Spotlight Text Update Electronic vocabulary Activity 3.4 Weathering, Erosion and Soil pg 116 HSC Spotlight Text

17. Part 2-Lesson 2 Soil as a resource that requires careful management

18. Water • Last lesson we discussed how wind is a means for erosion. Today we are going to discuss another powerful erosion agent: Water.

19. 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.

20. 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.

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

22. 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.

23. 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?

24. 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.

25. 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.

26. Water • These early practices has left hectares of useless land. Today most farmers are more careful about stripping fields of vegetation.

27. 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.

28. Activity • Science Skills pg 117 HSC Spotlight Text

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

30. Part 2-Lesson 3 Soil as a resource that requires careful management

31. Soil And Urban Development • Agriculture is not the only human activity that affects the rate of soil erosion. Urban development also plays a role.

32. 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.

33. Soil Compaction Lab Prep • Read and discuss the lab in preparation for next lesson.

34. Homework Complete DOT Point 2.1 page 57 Finish outstanding homework