Soil Science


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Soil Science

  1. 1. Soils Ag Science
  2. 2. Soil <ul><li>Soil is a layer on the earth’s crust that provides a combination of resources. Allow for the growth of plants and animals. </li></ul><ul><ul><li>Oxygen – needed for adequate root growth </li></ul></ul><ul><ul><li>Temperature – soil absorbs heat from the sun. Used for plant growth and seed germination </li></ul></ul>
  3. 3. <ul><ul><li>C. Water – used for plant growth </li></ul></ul><ul><ul><li>D. Carbon – utilized in the form of organic matter </li></ul></ul><ul><ul><li>E. Nutrients – provided as minerals. Broken down as nitrogen and recycled through decaying material. </li></ul></ul>
  4. 4. II. Soil is composed of 4 different components. <ul><li>Solid Portion (50%) </li></ul><ul><ul><li>Mineral Matter – 45% of the soil. Partially decomposed rock, ie. sand, silt, clay </li></ul></ul><ul><ul><li>Organic Matter - ~5% of the soil. Partially decomposed plant & animal material. Gives soil its color </li></ul></ul>
  5. 5. <ul><li>B. Pore spaces (50% of the soil) </li></ul><ul><li>1. Air – accounts for 25% of the soil. When soils are wet, less air. When soils are dry, more air. </li></ul><ul><li>2. Water – accounts for 25% of the soil. When it rains, water either enters the soil or runs off. </li></ul>
  6. 6. <ul><li>Water cont. </li></ul><ul><li>Infiltration – process of water soaking into the soil. </li></ul><ul><li>Once water is in the soil, the movement downward is called percolation . </li></ul><ul><li>A soil that allows for both is called permeable </li></ul>
  7. 7. <ul><li>Water in the soil my be one of three types </li></ul><ul><ul><li>Gravitational water – water that drains through the pore spaces (leaching occurs) </li></ul></ul><ul><ul><li>Capillary water – water that is held between particles of soil against forces of gravity; may move upward or sideways </li></ul></ul><ul><ul><li>Hygroscopic water – water that forms a thin film around individual soil particles; unavailable to plants. </li></ul></ul>
  8. 8. III. Abundant life can be found in soil. <ul><li>Forms of life in the soil include: </li></ul><ul><ul><li>Earthworms </li></ul></ul><ul><ul><li>Insects </li></ul></ul><ul><ul><li>Bacteria </li></ul></ul><ul><ul><li>Fungi </li></ul></ul><ul><ul><li>Other organisms </li></ul></ul><ul><li>Bacteria & fungi have an important role in the soil. They breakdown o.m. and release nutrients </li></ul>
  9. 9. <ul><li>C. Earworms, ants, crawfish, moles, and other organisms improve the tilth, or ease at which soil can be worked. </li></ul><ul><li>These organisms create openings in the soil as they tunnel. This helps drainage and improves gas exchange. </li></ul>
  10. 10. IV. Plants depend on soil to provide 4 basic needs. <ul><li>A. Anchorage – soil acts to provide a firm support as roots grow throughout the soil. </li></ul><ul><li>B. Water – soil provides nearly all of the water used by plants. Water is absorbed through the plants’ roots. </li></ul><ul><li>C. Oxygen – nearly all organisms need oxygen. Roots don’t have ample supplies, so they need good soil aeration to allow gas exchange. </li></ul>
  11. 11. <ul><li>D. Nutrients – of the 16 nutrients considered to be essential for plant growth, 13 are obtained from the soil. Root hairs absorb the nutrients dissolved in soil water. </li></ul>
  12. 12. V. Ag depends on soil to grow food, fiber, and other plants. <ul><li>Cropland – land on which soil is worked </li></ul><ul><li>Grazing land – land used for grazing cattle and sheep; perennial forage. </li></ul><ul><li>Forests – land used for growing trees, which is later harvested </li></ul><ul><li>Water structures – ponds and other reservoirs are constructed out of soil. </li></ul>
  13. 13. Non-ag uses of soil <ul><li>Recreation – playgrounds, sports fields, jogging paths, golf courses, parks, camp grounds,etc. </li></ul><ul><li>Foundations – buildings depend on a solid soil base upon which a building is to be built and remain sound. </li></ul><ul><li>Waste disposal – used for the treatment of human sanitary wastes. </li></ul><ul><li>Building materials – build underground, into hillsides, adobe </li></ul>
  14. 14. Five factors that affect soil formation <ul><li>A. Parent Material – type of rock that soil is made from. </li></ul>Igneous sedimentary metamorphic
  15. 15. <ul><li>B. Climate – temperature & moisture </li></ul><ul><li>C. Living organisms – organisms (bugs & worms) and plants in the soil. </li></ul><ul><li>D. Topography – hills and valleys </li></ul><ul><li>E. Time or weathering – age of the soil and climate </li></ul>
  16. 16. THE MAIN KINDS OF SOIL PARENT MATERIALS Parent material is formed by the disintegration and decomposition of rock
  17. 17. <ul><li>A. Most soils in Illinois were formed by glaciers. </li></ul>
  18. 18. Newer and more productive Older and less productive
  19. 19. <ul><li>B. About 64% of the soil is formed from loess. Loess occurred from the </li></ul><ul><li>blowing of the soil after the </li></ul><ul><li>glaciers. </li></ul>
  20. 20. <ul><li>C. About 7% of the state soil is due to recent stream deposits. This is referred to as alluvium . </li></ul><ul><li>D. Bedrock – most of the shale, sandstone, or limestone bedrock in Illinois is buried by loess. Except in extreme NW and Southern Illinois. </li></ul>
  21. 21. <ul><li>Organic soils – less than 1% of the soils in Illinois are classified as organic. Occur where formerly shallow ponds or supported swamp vegetation. Wet conditions slow decay of organic materials. </li></ul><ul><ul><li>Two types: muck and peat </li></ul></ul>
  22. 22. <ul><li>Topography is the slope characteristics of land. </li></ul>
  23. 23. How do living organisms affect the soil? <ul><li>Organisms living in the soil, like plants, insects and microbes actively affect soil formation. </li></ul>
  24. 24. <ul><li>Native Vegetation has </li></ul><ul><li>the greatest affect on </li></ul><ul><li>the development of </li></ul><ul><li>soil – plants that once </li></ul><ul><li>grew in it. </li></ul><ul><li>Two primary types </li></ul><ul><ul><li>Tall grass prairie </li></ul></ul><ul><ul><li>Deciduous hard wood </li></ul></ul><ul><ul><li>forest </li></ul></ul>
  25. 25. <ul><li>Prairie soils have a dark and deep surface layer. The roots of the prairie grass filled the top of the soil. </li></ul>
  26. 26. <ul><li>B. Timber soils tend to have a thin, moderately dark layer. Due to organic matter accumulating on the surface and decaying quickly. </li></ul>
  27. 27. Weathering <ul><li>Physical weathering </li></ul><ul><ul><li>The affects of climatic factors such as temperature, water, and wind. Freezing and thawing are a major contributor. </li></ul></ul>
  28. 28. Weathing (cont.) <ul><li>2. Chemical weathering </li></ul><ul><li>a. changes the chemical makeup of rock and breaks it down. Rainwater can dissolve minerals. </li></ul><ul><li>b. Some minerals react with oxygen. Oxidation further decomposes rock. </li></ul>
  29. 29. Weathering (cont.) <ul><li>B. Weathering causes soil to: </li></ul><ul><li>1. Develop </li></ul><ul><li>2. Mature </li></ul><ul><li>3. Age </li></ul>
  30. 30. Climate <ul><li>Refers to rainfall, freezing, thawing, wind, and sunlight. </li></ul>
  31. 31. Climate (cont) <ul><li>B. The climate in Illinois is said to be of the continental type. </li></ul><ul><li>Hot Summers, Cold Winter </li></ul>
  32. 32. Climate (cont.) <ul><li>C. Rainfall and Wind wear the rock away a little at a time. </li></ul>
  33. 33. Physical Features of soil <ul><li>Soils have many features that are used to recognize the difference between them. They include: </li></ul><ul><li>A. Texture – coarseness of fineness of soil particles </li></ul><ul><li>B. Structure – the way in which soil particles are held together </li></ul><ul><li>C. Depth of horizons – depth of each soil </li></ul><ul><li>D. Color – darkness or lightness of soil color </li></ul>
  34. 34. Colors <ul><li>Very Dark - ~5% O.M. </li></ul><ul><li>Dark - ~ 3.5% O.M. </li></ul><ul><li>Moderately Dark - ~ 2.5% O.M. </li></ul><ul><li>Light - ~2% O.M. </li></ul><ul><li>Very Light - ~1.5% O.M. </li></ul>
  35. 35. Soil Texture <ul><li>Soil Texture is the fineness or coarseness of a soil. </li></ul><ul><ul><li>Sand – largest particle </li></ul></ul><ul><ul><li>Silt – medium sized particle </li></ul></ul><ul><ul><li>Clay – small particle </li></ul></ul>Sand Silt Clay
  36. 37. Texture (cont.) <ul><li>B. Texture is important because it affects: </li></ul><ul><li>1. Water holding capacity – the ability of a soil to retain water for use. </li></ul><ul><li>2. Permeability – ease with which air & water my pass through the soil. </li></ul><ul><li>3. Soil Workability – the ease with which soil may be tilled and amount of time after rain. </li></ul><ul><li>4. Ability for plants to grow, ie carrots </li></ul>
  37. 38. Texture (cont.) <ul><li>Soil texture may be determined in 2 ways </li></ul><ul><ul><li>1. Using a textural triangle. This is found be using the percentage of each type of soil particle. </li></ul></ul>
  38. 39. Textural Triangle
  39. 40. Ribbon Method <ul><li>Fine textured </li></ul><ul><li>Moderately fine textured </li></ul><ul><li>Medium textured </li></ul><ul><li>Moderately coarse </li></ul><ul><li>Coarse </li></ul>
  40. 41. Ribbon testing Ball of clay made in fist Starting to form a ribbon Clay Ribbon (>2&quot;) Starting to make a ribbon from sand Ribbons are hard to form with sand (<1&quot;)
  41. 42. Soil Structures <ul><li>Granular </li></ul><ul><li>Crumb </li></ul><ul><li>Platy </li></ul><ul><li>Prismatic or Columnar </li></ul><ul><li>Blocky </li></ul><ul><li>Structureless </li></ul><ul><ul><li>Single grain </li></ul></ul><ul><ul><li>Massive </li></ul></ul>
  42. 43. Soil Structure
  43. 44. Soil Structure
  44. 45. Soil Structure
  45. 46. Soil Structure
  46. 47. Soil Structure
  47. 48. Soil Structure
  48. 49. Soil Structure
  49. 51. Soil Profile <ul><li>A soil profile is a vertical cross section of soil. </li></ul><ul><ul><li>Each layer may be different </li></ul></ul><ul><ul><li>A soil profile is usually studied to a depth of 3 to 5 feet. </li></ul></ul>
  50. 52. Soil Profile
  51. 53. Changes in soil <ul><li>II. Soils change over time in response to their environment. </li></ul><ul><li>A. The causes can be classified as: </li></ul><ul><li>1. Additions </li></ul><ul><li>2. Losses </li></ul><ul><li>3. Translocation </li></ul><ul><li>4. Transformation </li></ul>
  52. 54. Soil Degradation <ul><li>Soil Degradation is lowering the quality of soil or loss of productivity. Occurs because people don’t understand the soil and consequences of its uses. </li></ul><ul><li>Results from: </li></ul><ul><ul><li>Construction </li></ul></ul><ul><ul><li>Contamination </li></ul></ul><ul><ul><li>Erosion </li></ul></ul>
  53. 55. Construction <ul><li>Construction is altering land by building: </li></ul><ul><ul><li>Roads </li></ul></ul><ul><ul><li>Houses </li></ul></ul><ul><ul><li>Offices </li></ul></ul><ul><ul><li>Factories </li></ul></ul><ul><ul><li>Other Structures </li></ul></ul>
  54. 57. Contamination <ul><li>Results when chemicals, oil, and other substances leak into the land. </li></ul>
  55. 58. <ul><li>D. Soil may be contaminated by Ag practices: </li></ul><ul><li>1. Too much fertilizer </li></ul><ul><li>2. Excess chemicals </li></ul><ul><li>3. Irrigation water contains salt </li></ul>
  56. 59. Soil Erosion <ul><li>IV. Soil erosion is the process by which soil is moved. </li></ul><ul><li>A. Natural causes (natural erosion) </li></ul><ul><li>1. Round off mountains, fills in valleys </li></ul><ul><li>Ex. Mississippi Delta </li></ul><ul><li>B. Human actions </li></ul><ul><li>1. Human activity, such as construction & plowing may cause accelerated erosion </li></ul><ul><li>a. removes topsoil at an excessive rate </li></ul>
  57. 60. Natural Erosion
  58. 61. Human actions accelerating
  59. 62. Soil Erosion
  60. 63. V. Other Sources <ul><li>Improper irrigation practices </li></ul><ul><ul><li>Salinization – accumulation of salts </li></ul></ul><ul><ul><li>Alkalinzation – accumulation of sodium </li></ul></ul><ul><ul><li>Waterlogging – supersaturation </li></ul></ul><ul><li>Not replacing plant nutrients </li></ul><ul><li>Pollution </li></ul><ul><li>Overgrazing, deforestation, desertification </li></ul><ul><li>Compaction </li></ul>
  61. 65. Summary <ul><li>Soil can be very fragile </li></ul><ul><li>Care must be taken to produce crops </li></ul><ul><li>Takes many, many years, to make new soil through weathering (1” > 1000 years) </li></ul>