1. Unit 4 Power point Chapter 8: Soils World Geography 3202/3200

2. Characteristics Texture Soil Profile Soil Types Threats to Soil Soils

4. Soil Characteristics 3 characteristics of soil that affect its VALUE for farming and growing vegetation a re: 1. Organic Content 2. Mineral Content 3. Soil Texture

5. Organic Content organic content (dead and decomposing material) Soil fertility is determined as a ratio of the organic content to the content of ground bed rock.

6. Mineral Content Provide nutrients for various plant life. Ex. Potassium, calcium, phosphorous, nitrates etc. Varies with precipitation! Ex. Heavy rains tend to leach soils removing minerals from the root region of soil.

7. Soil Texture (pg. 138) rrefers to the mixture of: fine particles (sand), very fine particles (silt) and extra fine particles (clay). TThe BEST texture for agriculture is an even mixture of each. (referred to as loam) LLOAM is a mixture of these particles that provide sufficient space to allow:  root penetration,  aeration (air flow),  nutrient flow and  drainage / water retention.

8. Triangular graph of Soil Texture Pg. 139 30% sand 50% clay 20% silt

9. Soil texture…results Sandy soil — very light & dries out swiftly. Water drains very quickly Silty soil — retains moisture & feels slippery when wet. Retains nutrients better than sand but does not dry out as quickly.

10. Soil texture…results Clay soil — a very heavy soil, it holds moisture for long periods of time when wet and dries hard as a brick.. Loam soil — the ideal soil texture, it is composed of sand, silt and clay. Loam is a separate category because none of its components account for more than 50%.

11. Soil Characteristics Most soils contain four basic components: Organic matter Mineral particles Water Air

12. Organic Content (Soil Characteristics) Plants and animals aid in the development of a soil through the addition of organic matter (Ie. When they die!). Fungi and bacteria decompose this organic matter This organic matter is known as humus, which is a source of nutrients for plant growth. Makes up the upper layer of the soil. Colored dark brown to black.

13. Mineral Content (Soil Characteristics) Originally part of rocks Broken down by weathering of rock Different particle sizes (sand, silt and clay) Some minerals are nutrients needed by plants for growth. (Calcium, potassium, phosphorous)

14. Water and Air (Soil Characteristics) About half of the total mass of soil is made of up vast interconnecting cavities or holes. Usually caused by worms, insects and small animals that tunnel through the soil. These holes are filled with both air and water. The amount of air and the amount of water filling these spaces varies dramatically throughout the year, and from location to location. BUT averages about half each.

15. Water and Air (continued) Plants need air around their roots in order to properly obtain nutrients required for growth. Plants need water to grow. Water enables physical and chemical weathering to create the various components of the soil. Water dissolves and carries minerals and nutrients required by plants to grow.

16. Soil Profile O Horizon – “Organic” HUMUS: detritus, leaf litter and other organic material lying on the surface. It is dark because of the decomposition. They decompose into nutrients that enrich the soils.

17. Soil Profile A Horizon – “Topsoil” darker than the lower layers. loose and crumbly with varying amounts or organic matter. most productive layer of soil.

18. Soil Profile B Horizon – “Subsoil” Light colored, dense, and low in organic matter. materials leached and eluviated from the topsoil accumulate here.

19. Soil Profile C Horizon – “Weathered Parent Material” transition area between soil and parent material. Partially disintegrated parent material. mineral particles. less organic/living matter.

20. Soil Advancement

21. Definitions - Humus is the accumulation of dead and decayed plant and animal matter that makes up the organic nature of soil. -Occurs where there is substantial plant and animal growth. - Leaching is the process where nutrients are washed down through the soil with the movement of liquids/water soluble minerals down the soil profile. -Occurs where there is substantial rainfall.

22. Definitions - Eluviation is the lateral or downward movement of (solids / insoluble minerals) clay and other fine materials in suspension. - Occurs where there is substantial rainfall. Capillary action results when water molecules are attracted to clay particles and drawn upward through the soil profile. -Minerals and salts are dissolved in soil by moisture -Occurs where it is substantially dry.

23. Questions Page 136 in text If time: #9 No need to define (see previous slides) #12 #15

24. Threats to Soil All countries face the threat of soil loss Soil can be easily damaged or eroded (and often in a very short period of time.) Example: water run-off can wash away soil, urban expansion, over grazing, flooding and deforestification

25. Threats to Soil Desertification: Because of this, over 20million hectares (ha) of soil is being ‘unsuitable’ for agriculture It is the loss of vegetation and organisms, and the expansion of degraded soil caused by the breakdown of the fragile ecological balance that exists in the world's drylands. It affects many areas of the world, frequently leading to food shortages and subsequently, social problems.

26. Soil Fertility Crop Rotation -One method of maintaining fertility is through ‘crop rotation’. -planting different crops in the same soil at different times For example, tomatoes are heavy eaters. So if you plant them in the exact same spot for a few years in a row, you are likely to deplete your soil of the nutrients that the tomatoes need. However, if you plant peas the year after you have planted tomatoes, the peas will help to return nitrogen to your soil, therefore helping to keep your soil and your garden healthy.

27. Reducing Soil Erosion There can be a reduction in soil erosion if sensitive methods and techniques are used. Methods such as 1. strip cropping 2. cover cropping 3. contour ploughing 4. terracing

28. Strip Cropping Growing crops in a systematic arrangement of strips across a field. Typesof strip cropping include contour, field or buffer. Purposes: Reduce soil erosion from water Reduce the transport of sediment and other waterborne contaminants Reduce soil erosion from wind Protect growing crops from damage by windborne soil particles Improve water quality

29. Cover Cropping A cover crop is a type of plant grown to suppress weeds, help build and improve soil, avoid exposure to rain and wind and control diseases and pests. Cover crops are also called "green manure" and "living mulches.“ Ex. Oats, Barley, Rye They're called "green manure" because they provide nutrients to the soil much like manure does. And as "living mulches," cover crops prevent soil erosion. Once grown, cover crops are usually mowed and then tilled into the soil, which increases the soil`s humas content prior to replanting

30. Contour Ploughing A ploughing methods that respects the natural shape, or contour lines, or a land area. By ploughing along the contour lines the farmer creates `mini terraces` which discourage swift water run off. Water doesn’t erode the soil, but rather soaks into it, and can be used by plants for growth

31. Terracing Man-made steps (shelves or terraces) built into hills or on the side of sloped land. Similar to contour ploughing, but occurs on a much larger scale It reduces soil erosion by water run-off and allows moisture to soak into the ground

32. Questions Page 141 Numbers 26, 27, 28

33. The Nature of Resources Humans have a wide range of demands Things they need for survival, pleasure or convenience Resources: Available assets, or sources of wealth, that benefit and fulfill the needs of a community our wide range of demands can be satisfied by these. Example. Oil/Gas: it gives us heat (survival) Animals: fur coats (pleasure), food (survival)

34. 3 types of Resources 1. Natural Resources: the natural source material found in the environment. 2. Capital Resources: ex, material resources that are purchased/produced to obtain natural resources. -ex. Money and equipment are required to extract, refine, process and develop oil. 3. Human Resources: entrepreneurs and workers that must organize and overlook the capital resources (that will lead to natural resources developed)

35. Necessary Conditions for a Resource For a resource to be ‘used’ there must be certain conditions. 1. Need or Want A culture or society must have a need or want that requires use of the material 2. Technological Development A culture or society must have the technology to extract/develop the resource 3. Profitability A culture or society must be able to develop and use the material profitably. Note: Conditions will vary from place to place

36. Categories of Natural Resources Inorganic Resources -non-living and unable to regenerate themselves -Example: oil, gold Organic Resources Living and renewable (can reproduce/replace themselves) Example: fish, corn Flora: All plants Fauna: All Animals Note: Reproduction in organic resources can be disrupted. Example: over fishing, over hunting

37. Soil as a Natural Resource Soil is one of the most important resources in the world. Why? Without it? No plants No forests No food

38. Questions A. Read the case study on page 133-134. Answer #5 a & b B. Answer #6 a,b&c, #7

39. 1.Describe the factors that affect soil quality. Hint: 4 points

40. Describe the factors that affect soil quality. Soil fertility is measured in terms of a soil’s humus content relative to the amount of ground-down bedrock it contains. Several factors determine this mixture: Leaching of soil will decrease the quality of soil and reduce the thickness of the topsoil layer (horizon “A”). Eluviation will decrease the amount of particles in the soil and will decrease the quality of the soil and the thickness of the topsoil layer. (horizon “A”) The higher the rate of accumulation of humus, the better the quality of the topsoil layer. Capillary Action increases the thickness of the topsoil layer (Horizon “A”) and therefore increases the quality of the soil.

41. 2.How would climatic conditions affect soil fertility in each of the following regions? Rainforest Temperate Grassland Tundra

42. How would climatic conditions affect soil fertility in each of the following regions? Rainforest: Have a soil known as LATOSOL, which although it does experience a great deal of accumulation of humus from the warm wet conditions, it also experiences a great deal of leaching and eluviation which causes the soil to be VERY INFERTILE. Temperate Grasslands: Moderate precipitation and temperate temperatures allow for the accumulation of humus, little leaching & eluviation, but a moderate amount of capillary action. Combined, this leads to a VERY FERTILE soil known as CHERNOZEM. Tundra: Cold year-round temperatures provide for little plant- growth and therefore little accumulation of humus. Cold temperatures also slow down the decay of plants and animals, while permafrost prevents adequate water drainage. Together this all creates a soil, known as TUNDRA SOILS, which are VERY INFERTILE.

43. Desertification is the loss of vegetation and organisms, and the expansion of degraded soil caused by the breakdown of the fragile ecological balance that exists in the world's drylands. It affects many areas of the world, frequently leading to food shortages and subsequently, social problems. 3. What is the main cause for deserification?

44. What is the main cause for desertification? It results when unpredictable climate variation (i.e. years of adequate rainfall are followed by prolonged periods of drought) are combined with unsustainable land-use practices (i.e. large increase in population in an area, overgrazing of animals, over cutting of forests etc.)

45. 4. Why does Africa and Asia suffer most from the threat of desertification?

46. Why does Africa and Asia suffer most from the threat of desertification? These regions have extensive dryland regions. These regions have experienced huge increases in population over the past fifty years. This has lead to overuse of the land in terms of overgrazing, water usage and deforestation. Hence desertification is occurring in these regions.

47. 5. Evaluate the validity of the following statement: “Soil is a plentiful resource”

48. Evaluate the validity of the following statement: “Soil is a plentiful resource” -Currently there is enough arable land to meet the demands placed upon it. Therefore it can be considered a plentiful resource. As humanity’s needs change and as the amount of arable land changes (through desertification, for example), soil may well cease to be a plentiful resource.