Animal, Plant & Soil Science Lesson D1-2 Soil Formation

1. Animal, Plant & Soil ScienceLesson D1-2Soil Formation

2. Interest Approach • Ask two students to sit or stand in front of the class. Ask the class if the students are exactly the same. Responses should be a resounding “No!” Ask the class what makes the students different from each other. One of the first responses should be that they have different parents. Relate this to different types of soil parent material. An additional answer should be that the students have grown up in different environments and have had different experiences. Relate this to different environments in which soils develop. You may even wish to ask students to think about identical twins who may have been separated as youngsters. As adults, there will be differences between them. Explain that even though the twins have the same genetic makeup, they have experienced different environments and situations. Relate the same concept to soil development.

3. Objectives • 1 Identify five factors involved in soil formation. • 2 Describe different types of parent material. • 3 Explain topography and how it affects soil formation. • 4 Explain how organisms affect soil development. • 5 Describe how time and weathering affect properties of soil. • 6 Examine how climate affects the development of soil.

4. Terms alluvium bedrock chemical weathering climate glacial till glacier loess native vegetation organic matter outwash parent material physical weathering prairie soil timber soil topography

5. What is soil? • The top layer of the Earth’s surface, suitable for the growth of plants. * Contains both organic and inorganic material • Soil was formed over many centuries • It is durable and could last as long as our species survives • So fragile it can be destroyed overnight • Cannot be replaced once it is destroyed.

6. Importance of Soil • Why is the management of our soil so important? • It is the backbone of life. • It supports plant growth. • It catches and stores our water. • It supports buildings and structures. • If mismanaged it can be destroyed very quickly.

8. What are five different factors that affect soil formation? I. Five primary factors affect the process of soil formation and development.

9. What are five different factors that affect soil formation? A. Parent material—the type of rock material from which the soil is formed B. Topography—the slope characteristics of the soil C. Living organisms—the organisms, including plant material, that live within the soil

10. What are five different factors that affect soil formation? D. Time or weathering—the age of the soil or the climate where the soil is found E. Climate—the temperature and moisture characteristics of the area where the soil was formed

11. What are some different types of parent material that affect soils? II. Parent material is formed by the disintegration and decomposition of rock. It isclassified according to the way it was moved and scattered.

12. What are some different types of parent material that affect soils? • A. Most soils in Illinois have been formed from material originally moved by glaciers. A glacier is a large, long-lasting river of ice that is formed on land and moves inresponse to gravity. Two major glaciers, the Illinoisan and the Wisconsinan, had the greatest influence on present-day soils in Illinois. The Illinoisan glacier originated thousands of years before the Wisconsinan glacier and covered nearly the entire state. Later, the Wisconsinan glacier covered slightly more than the northeastern third of Illinois. Soils in southern Illinois are much older and less productive than those in northern Illinois. Soils of glacial origin are classified as loess, outwash, or glacial till.

14. What are some different types of parent material that affect soils? 1. About 64 percent of the soil in Illinois has been formed from loess. Loess has developed some of the best soil in the state. Loess originated from the blowing of the soil after the glaciers melted and dried. It is the single most desirable soil parent material. This is due to its well-balanced mineral content, medium texture, and excellent water-holding capacity.

15. What are some different types of parent material that affect soils? 2. About 16 percent of the soil in Illinois has been formed from outwash. This type of soil is most extensive in northern Illinois. Outwash originated when the glaciers melted. The melted waters carried the gravelly materials away to be deposited below the glacial ridges. Sandy outwash was carried farther downstream, and the finer materials—silt and clay—were deposited in lakebeds or slow-moving streams.

16. What are some different types of parent material that affect soils? 3. About 11 percent of the soil in Illinois is from glacial till. It is found primarily in northeastern Illinois. Glacial till is parent material that was physically moved and deposited by the glacier itself. It often contains a variety of sizes of soil particles that have not been layered from the effects of wind or water, as have the other two types of glacial soils. Pebbles and various sizes of boulders are common in till.

17. What are some different types of parent material that affect soils? B. About 7 percent of the soil in Illinois is a result of recent sediments deposited by streams as they flood. It is referred to as alluvium. Alluvium is generally a water-borne material deposited on bottomlands.

18. What are some different types of parent material that affect soils? C. Bedrock is solid rock usually under the soil or other loose material. Most of the shale, sandstone, or limestone bedrock in Illinois is buried by loess, outwash, glacial till, or alluvium. However, in the unglaciated areas of northwestern and extreme southern Illinois, weathered bedrock has provided soil parent material. About 2 percent of the soil in Illinois can be attributed to bedrock or thinly covered bedrock.

19. 2. Rocks aggregates of minerals • (3 groups) • Igneous – rock formed by cooling of molten materials and pushed up to the earths surface – lava, magma • Sedimentary – formed by solidification of sediment (3/4 of the earths surface is covered by this) • Metamorphic- igneous or sedimentary rocks that have been reformed because of great heat or pressure

20. Marine deposits • Deposits left from ancient ocean floor • Lacustrine deposits • Deposits left by lakes • Colluvial deposits • Left by gravity • Organic deposits • Left in swampy and marshy areas • Peat- contains recognizable plant materials • Muck- completely decayed so that plant parts are no longer recognizable

21. What are some different types of parent material that affect soils? D. Organic matter is decayed or partially decayed plants and animals, roots, and living organisms. Less than 1 percent of the soil in Illinois is classified as organic. Organic soil is found where formerly shallow ponds supported swamp vegetation. The wet conditions slowed decay of the dead plants so that organic matter could accumulate. The two types of organic soil are peat and muck. Muck is more decomposed than peat.

22. What is topography, and how does it affect the development of soil? • III. Topography is the slope characteristics of a soil. It includes the degree or steepness, length, shape, and direction of a slope. These factors influence the amount of rainwater runoff or the amount that enters the soil or collects in small depressions on the soil surface. Soils on steep slopes have higher amounts of runoff and erosion than those on level topography. The amount of moisture in the soil during its development affects the rate of weathering and the subsoil colors. Soils in depressions and on nearly level topography are likely to have poor or very poor natural drainage. Soils on moderately sloping to steep topography are usually well drained.

23. Topography • Lay of the land • Items in topography include • Slope • Drainage • Plants around

24. Slope and drainage affect soil formation both directly and indirectly. • Steep slopes cause soil runoff of water. • Breaks up soil. • Adds deposits to lower levels • Exposes lower layer of soil (subsoil). • Percolation – process in which water passes through the soil. • Soils on level land = poor drainage • Soils on sloped land = better drainage

25. Drainage affects water table • When soil is saturated little or no air can penetrate. • Lack of air reduces action of microbes and other soil forming activities. • Poor air and water movement causes marbling. • Marbling – discoloration of the soil. • Poor drainage and excessive water retards plant growth.

26. Drainage affects water table • When soil is saturated little or no air can penetrate. • Lack of air reduces action of microbes and other soil forming activities. • Poor air and water movement causes marbling. • Marbling – discoloration of the soil. • Poor drainage and excessive water retards plant growth.

27. Slope • Amount of rise and fall of the land in a set 100 feet. • Rise/Run • Given as a percentage. • There is a 12 foot rise in 75 feet. • 12/75 = 16% slope

28. How do living organisms affect the development of soil? IV. Organisms that live in soil—plants, animals, and microbes—actively affect soil formation.

29. How do living organisms affect the development of soil? A. The greatest effect on the development of soil is from plants that once grew in it. These plants are referred to as native vegetation. Native vegetation determines the kind and amount of organic matter in the soil. In Illinois, there are two primary types of native vegetation: tall prairie grass and deciduous-hardwood forests. Soils in the areas of this vegetation are called prairie soil and timber soil.

30. How do living organisms affect the development of soil? • 1. Prairie soil has a dark and deep surface layer. This is because roots from the prairie grass filled the top of the soil to a depth of 1 to 2 feet or more. Partial decay of these roots over a long period gave the soil high organic-matter content. • 2. Timber soil tends to have a thin, moderately dark layer. This is due to organic matter accumulating on the surface, where decay occurs more rapidly. When tilled, this dark material is mixed with the soil below to produce a lighter color.

31. How do living organisms affect the development of soil? B. Other living matter that influences the development of soil includes various kinds of animal life. Earthworms, crawfish, ground squirrels and other burrowing animals, and various insects that incorporate organic matter into the soil are examples.

32. Living Organisms • Causes the decay of organic material • Microbes are microscopic plants and animals, which help in the decaying process. • Release CO2 and other essential compounds • Insects, worms, and help in this process by mixing the various soil materials.

33. What is weathering? How does weathering and time affect soil? V. Weathering plays a major role in the formation of soil. Weathering is the decomposition of rocks.

34. What is weathering? How does weathering and time affect soil? • A. There are two types of weathering: • 1. Physical weathering—the effects of climatic factors, such as temperature, water, and wind. Freezing and thawing is a major contributor to physical weathering. • 2. Chemical weathering—the effects of factors that change the elemental makeup of rock and break it down. Rainwater is mildly acidic and can slowly dissolve many soil minerals. Some minerals react with oxygen in the atmosphere. Oxidation further acts to decompose rock.

35. What is weathering? How does weathering and time affect soil? • B. Weathering causes soil to develop, mature, and age. • 1. Develop—Soil develops rapidly. Plant nutrients are released, and organic matter accumulates. Soils will develop faster in humid regions than in arid regions. • 2. Mature—Mature soil is at peak productivity, with a high amount of organic matter. Water begins leaching away nutrients, and plant growth starts to decline. This results in less organic matter. • 3. Age—Minerals continue to break down, and clay is leached into the subsoil. The soil becomes lighter in color from less organic matter.

36. How does climate affect soil development? • VI. Elements of climate influence soil formation. Climate is the weather in a region overa long period. Three elements of climate related to soil development are temperature, rainfall, and wind. These factors are either directly or indirectly responsible for the breakdown of rocks and minerals, the release of plant nutrients, and many other processes affecting the development of soils.

37. Climate and Location • Greatly affects the rate of weathering by the temperature. • The warmer the temperature the more organisms there are. • This increases the chemical reaction time in breaking down materials. • Slope and location of a field also affect erosion and drainage. • High Temperatures along with tree cover and moisture on leaf residue = acidic soils

38. How does climate affect soil development? A. The climate in Illinois is said to be of the continental type. It is characterized by hot summers and cold winters. This climate enhances the weathering process through freezing and thawing.

39. How does climate affect soil development? B. Rainfall during the growing season is similar across the state; however, southern Illinois receives more rainfall during the winter and early spring. Soils in humid regions are subject to more leaching than soils in dry regions. Rainfall wears the rock away a little at a time.

40. Areas of High rainfall are usually leached and somewhat acidic. • Leaching – process in which contents are removed from the soil • To much water prevents or describes microbial growth and may exclude air by water logging. • Water and temperature have the effect of swelling and contracting of soil particles.

41. How does climate affect soil development? C. Wind also wears the rock away. Particles carried by the wind strike the rock and wear it down.

42. REVIEW • 1. What are five different factors that affect soil formation? • 2. What are some different types of parent material that affect soils? • 3. What are some different types of parent material that affect soils? • 4. What is topography, and how does it affect the development of soil? • 5. How do living organisms affect the development of soil? • 6. How does climate affect soil development?