Soil 101 Everything you need to know!

1. Soil 101Everything you need to know! Ms. Brown

2. Part 2: Understanding Soil Formation

3. Identify five factors involved in soil formation. Parent material: Type of rock material the soil is formed from. Climate: Temperature and moisture characteristics of the area in which the soil was formed. Living organisms: The organisms, including plant material, that live within the soil. Topography: Slope characteristics of the soil Time or weathering: Age of the soil and its climate.

4. Types of Parent Material • Parent materials are formed by the disintegration and decomposition of rock. • They are classified according to the way they were moved and scattered.

5. Types of Parent Material

6. Bed Rock • Bedrock most of the shale, sandstone, or limestone bedrock is buried by loess, glacial till, outwash, or alluvium. • However, in the unglaciated areas weathered bedrock has provided soil parent material.

7. Organic Matter • Organic matter: Organic soils occur 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 soils are referred to as peat and muck. • Muck is more decomposed than peat

8. How Topography Affects Soil Formation • Topography refers to 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.

9. How Organisms Affect Soil Development • Two types of native vegetation: • tall prairie grass --- prairie soils • deciduous-hardwood forests--timber soils. • Prairie soils have 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 of time gave these soils a high organic matter content.

10. How Organisms Affect Soil Development • Timber soils tend 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. • 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 which incorporate organic matter into the soil are examples.

11. Types of Weathering

12. Weathering causes soil to: • Develop rapidly, plant nutrients are released, and organic matter accumulates. • Soils will develop faster in humid regions than in arid regions.

13. 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. • Minerals continue to break down and clay is leached into the subsoil. • The soil becomes lighter in color from less organic matter.

14. How Climate Affects Soil Development • Climate refers to rainfall, freezing, thawing, wind, and sunlight. • 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.

15. What is Soil Texture? • Soil texture is the fineness or coarseness of a soil. • It describes the proportion of three sizes of soil particles. These are: • Sand - large particle • Silt - medium sized particle • Clay - small particle

17. What does Texture Affect? • Soil workability the ease with which soil may be tilled and the timing of working the soil after a rain • Ability of plants to grow some root crops like carrots and onions will have difficulty growing in a fine-textured soil

18. Determining Soil Texture • Soil texture may be determined in one of two ways: • The percentages of sand, silt, and clay may be tested in the lab. • Once tested, you may determine the textural class of the soil by referring to the textural triangle. • The ribbon method.

19. Notice the Shape and Size of the These Soil Particle Types

20. Textural Triangle Understanding the Textural Triangle and Determining Soil Texture Worksheet: Part 1

21. LAB TIME!!! • Determining Soil Texture by the Ribbon Method

22. Soil ProfilesWhat is a Soil Profile? • A soil profile is a vertical cross-section of the soil. • When exposed, various layers of soil should be apparent. • Each layer of soil may be different from the rest in a physical or chemical way. • The differences are developed from the interaction of such soil-forming factors as: • Parent material • Slope • Weathering (time) • Climate • Native vegetation A soil profile is usually studied to a depth of 3 to 5 feet.

24. What are the major horizons of a soil profile and how do they differ? • There are 3 primary soil horizons called master horizons. • A Horizon • B Horizon • C Horizon

25. A Horizon. This is often referred to as topsoil and is the surface layer where organic matter accumulates. Over time, this layer loses clay, iron, and other materials due to leaching. This is called eluviation. The A horizon provides the best environment for the growth of plant roots, microorganisms, and other life. • O Horizon. • This is an organic layer made up of partially decayed plant and animal debris. • It generally occurs in undisturbed soil such as in a forest.

26. B Horizon. This horizon is referred to as the subsoil. It is often called the “zone of accumulation” since chemicals leached from the A and E horizons accumulate here. • E Horizon. • This is the zone of greatest eluviation. • Because the clay, chemicals, and organic matter are very leached, the color of the E horizon is very light. • It usually occurs in sandy forest soils with high amounts of rainfall.

27. B Horizon • This accumulation is called illuviation. The B horizon will have less organic matter and more clay than the A horizon. • Together, the A, E, and B horizons are known as the solum. • This is where most of the plant roots grow.

28. C Horizon • This horizon is referred to as the substratum. • It lacks the properties of the A and B horizons since it is influenced less by the soil forming processes. • It is usually the parent material of the soil.

29. R Horizon • This is the underlying bedrock, such as limestone, sandstone, or granite. • It is found beneath the C horizon.

30. Soil Profile Horizons • O Horizon organic layer of leaves, roots,and decaying material • A Horizon Topsoil • B Horizon Subsoil • C Horizon Substratum • R Horizon Bedrock or solid rock below the C Horizon

31. How do soils within a soil profile change over time? • Soils change over time in response to their environment. • The environment is influenced by the soil-forming factors.

32. The causes of these changes can be classified into 4 processes: • Additions. Materials such as fallen leaves, wind-blown dust, or chemicals from air pollution that may be added to the soil. • Losses. Materials may be lost from the soil as a result of deep leaching or erosion from the surface. • Translocations. Materials may be moved within the soil. • This can occur with deeper leaching into the soil or upward movement caused by evaporating water • Transformations. Materials may be altered in the soil. • Examples include organic matter decay, weathering of minerals to smaller particles, or chemical reactions.

33. Understanding Soil Color • What are physical features used to differentiate between soils? • Texture coarseness or fineness of soil particles • Structure the way in which soil particles are held together • Depth of horizons the depth of each soil • Color refers to the darkness or lightness of the soil color

34. What are the colors used to describe surface soils? • Colors associated with surface soils are dependent on the amount of organic matter found in them. • Colors may be classified as: • Very Dark: approximately 5% organic matter • Dark approximately 3.5% organic matter • Moderately dark approximately 2.5% organic matter • Light approximately 2% organic matter • Very light approximately 1.5% organic matter

35. The amount of organic matter is the factor used to determine the color of the surface soil.The amount of organic matter is determined by the kind of native vegetation. Native vegetation refers to the type of plant material that grew on the soil.

36. What colors are used to describe subsoil? • Subsoil colors are associated with natural drainage of the soils. • This is the drainage condition that existed when the soil was forming. • Subsoil colors are classified as: • Bright-colored brown, reddish brown, or yellowish brown • Dull-colored gray or olive gray • Mottle-colored clumps of both bright and dull colors mixed together

37. What factors determine the color of subsoil? • The color of subsoil is determined by the status of iron compounds. • These are determined by the type of drainage found in the soil as it formed. Good drainage provides subsoil that is bright in color. • This is because the iron found in these soils has been oxidized. • This can be compared to metal that oxidizes or rusts when both moisture and air are present. • Rust has a bright or orange color.

38. What factors determine the color of subsoil? • Poor drainage provides subsoil that is dull or gray in color. • This is because the iron found in those soils has not been subject to air or oxygen. • The iron compounds do not oxidize. • This leaves a grayish color.

39. What factors determine the color of subsoil? • Somewhat poor drainage provides subsoils that are mottled. • This is because the soil was saturated with moisture for certain periods. • This leaves a gray color in some soil clumps. • Since the soil was comparatively dry during other periods, it left a bright color in other soil clumps.

40. How do parent material, age, and slope affect the color of soil? • In addition to organic matter and drainage, soil color may also be affected by other factors: • parent material • age • slope

41. Age As soils age, much of the darker color is lost due to the weathering process. This causes the soil to lose organic matter.Slope Soil on top of hills is usually lighter in color than the soil in depressions or on level ground.This is partly due to the darker topsoil being washed off the hills. This leaves the lighter subsurface or subsoil exposed. Parent Material • The color of a soil is associated with the kind of material from which it is formed. • Soils that are developed from sand or light-colored rock will be lighter. • Those developed from darker materials such as peat or muck, will be darker in color.

42. Lab Time • Making Your Own Soil Profile • Part 1: Illustrating the Soil Profile You are creating! • Part 2: Creating your Own Edible Soil Profile

43. Understanding Water Holding Ability • What is Moisture holding Capacity? • Moisture holding capacity is the ability of the soil within the soil profile to retain water.

44. What is available to the plants? • Available soil moisture is the water in the soil that can be used by plants. • When moisture levels are high, plants can easily extract moisture from the soil. • As the water is used, soil moisture tension increases. • Soil moisture tension is the force by which soil particles hold on to moisture.

45. How do we determine how much moisture the soil can hold? • Moisture holding capacity is determined primarily by the soils texture. • As a rule, the finer the texture of the soil, the more moisture it will hold. • A soil high in sand will hold less water. • Soils high in clay, hold water and keep it from percolating out of the root zone. • If the soil is entirely clay, it will hold the water too tightly. • This means less water is available to plants than if silt were present. • A good silt loam holds the most moisture available for plants

47. The amount of moisture the soil can hold for plants is referred to as available water holding capacity.

48. Available water holding capacity depends on: • 1. How deep the soil profile is. • 2. The type of soil texture found throughout the soil profile. • On average, the following textures will hold the designated amount of moisture per inch of soil: • fine textured .20 inches • moderately fine textured .25 inches • medium textured .30 inches • moderately coarse textured .20 inches • coarse textured .10 inches

49. How do you know figure the water holding capacity • To determine the available water holding capacity for a given area, multiply the depth of each horizon, to a maximum depth of 60 inches, by the amount of water the texture within that horizon can hold. • Add the totals for each horizon to calculate total water holding capacity.

50. Example • A horizon: 9 inches deep, medium texture = 9 × .30 =2.70 inches • B horizon: 23 inches deep, moderately fine texture = 23 × .25 = 5.75 inches • C horizon: 28 inches deep, medium texture = 28 x .30 = 8.40 inches • Total = 16.85 inches of water