Soil Science

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