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Soil Science

Soil Science. Horticulture/Natural Resources Sutherlin High School AST September 16, 2013. What is Soil?. Dynamic, living interface between the atmosphere and rock. Functions of Soil. Anchor and nutrients for plants Habitat for animals Recycle waste through decomposition

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Soil Science

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  1. Soil Science Horticulture/Natural Resources Sutherlin High School AST September 16, 2013

  2. What is Soil? • Dynamic, living interface between the atmosphere and rock

  3. Functions of Soil • Anchor and nutrients for plants • Habitat for animals • Recycle waste through decomposition • Cleanse and store water • Engineering uses

  4. Components of Soil • Solids • Mineral • Organic Matter • Pore Space • Water • Air

  5. Soil Forming Factors • Climate - temperature and precipitation • Organisms - type of biology present • Relief/ Topography – where is the water, where are the people

  6. Soil Forming Factors • Parent Material - soil minerals and particle size impact drainage and filtration • Time - influences ability of soil to extract pollutants physically and tie up nutrients biologically

  7. Active Factors Passive Factors Soil = f(cl,o,r,p,t) • Climate • Organisms • Topography/relief • Parent Material • Time Which one can we change?

  8. Mineral and Texture • Minerals in soil: • Sand • Silt • Clay

  9. Mineral and Texture

  10. Mineral and Texture • Sand/Loamy Sand (Course) • Sandy Loam (Moderately Course) • Loam/Silt Loam (Medium) • Clay Loam/Sandy Clay Loam/Silty Clay Loam (Moderately Fine) • Clay/Sandy Clay/Silty Clay (Fine)

  11. Mineral and Texture • Surface area per unit volume • 1 g sand ~ 0.1 m2 • 1 g silt ~ 1 m2 • 1 g clay ~ 10-1000 m2

  12. Mineral and Texture Coarse textured soils larger pores Fine textured soils greater total pore space Clay Sand

  13. Mineral and Texture Low Medium High Good Poor Medium High Slow Very slow Low Medium High

  14. Mineral and Texture • Clay

  15. Root zone Mineral and Texture

  16. Horizons • Master Horizons • Special Horizons

  17. Soil Color • Result of soil elements, organic matter, wetness

  18. Soil Color • Described using the Munsell Color System

  19. Soil Color • Listed as a number system • hue (a specific color) • value (lightness and darkness) • chroma (color intensity)

  20. Soil Color • Color Characteristics • Black/dark brown: high organic matter • Brown: well-drained, aerated • Grey: wet, color-less • Red: old, well established (oxidized) • Red or Yellow: presence of iron oxides • White: leached

  21. Soil Color • Color Categories • Black/Dark Brown • Brown/Light Brown/Yellowish Brown • Reddish Brown/Red • Grey/Light Grey/White

  22. Soil Structure • Soil breaks down to units called peds • Particles bound together

  23. Soil Structure • Peds come in multiple structure shapes • Blocky • Prismatic • Platy • Columnar • Granular

  24. Soil Structure • Soil without ped structure is considered structureless • Single-grained: sands • Massive: clay layers • No natural breaks into peds

  25. Soil Structure • Structure Grade • Ability of peds to hold together • Stronger structure grade=peds easier to see and separate from one another (clear breaks)

  26. Soil Structure • Structure Grade Categories • Strong (very easy to see/separate) • Moderate • Weak (difficult to see/separate) • Structureless (no structure)

  27. Mottles • Redox (reduction-oxidation) reactions • Caused by periodic or seasonal saturation of soil • Indication of wetness

  28. Mottles • Mottles used to determine internal drainage of soil • Excessively drained soil: 40”+ of coarse/ moderately coarse • Well-Drained: No mottles in the top 40” • Moderately-Well Drained: No mottles in the top 24” • Somewhat Poorly Drained: No mottles in the top 8” • Poorly Drained: Mottles in the top 8”

  29. Mottles

  30. Coarse Fragments • Non-soil fragments over 2mm in diameter • Coarse fragments decrease water holding capacity • Percentagecoarsefragments vsPercentage soil

  31. Special Features

  32. Soil Orders and Naming

  33. Properties of the Whole Soil

  34. Effective Depth • Ability for roots to penetrate soil depth • Inhibited by impermeable layers • Bedrock • Massive clay layer? • Durapan? • Cr?

  35. Effective Depth • Available water calculations only matter where roots can reach • Look for root depths

  36. Available Water Holding Capacity • Amount of water available for plants • Measured in inches water/inch of soil

  37. Available Water Holding Capacity • A factor of texture • Values vary depending on clay content • Calculated by = Inches of soil X texture value X % soil

  38. Soil Permeability • Speed of water’s ability to move through the soil • Affected by texture and structure grade

  39. Soil Permeability • Surface permeability determined using the first mineral horizon (A) • Subsoil permeability determined using the slowest permeable layer above 30 inches of depth

  40. Erosion • Erosion is a factor for the surface horizon • Wind Erosion • Only a factor in Eastern Oregon • Water Erosion • Factor of texture and slope

  41. Erosion • Management practices affecting erosion • Vegetation • Water flow management (ditches/diversions) • Tilling vs no-till

  42. Internal Drainage • Indicator of how often the site is saturated, and at what level • Determined by mottles • Use mottle rules

  43. Parent Material • How did the soil form/arrive there • Residuum – resides in place • Colluvium – moved by gravity

  44. Parent Material • Alluvium – moved by water • Old: older than 100 years • Recent: within last 100 years

  45. Parent Material • Lacustrine – old lake bed • Wind-blown sand (eolian)/silts (loess) • Volcanic ash

  46. Relief/Site Position • Uplands (Residuum) • Footslope (Colluvium) • Fan (Recent alluvium) • Stream Terrace (Old alluvium) • Floodplain (Recent alluvium)

  47. Slope

  48. Stoniness/Rockiness • Amount of large surface rocks greater than 10” in diameter

  49. Stoniness/Rockiness • Inhibits surface tillage • None • Stony/Rocky (1 every 30 to 100 feet) • Very stony/rocky (1 every 5 to 30 feet) • Extremely stony/rocky (more than 3% of the surface)

  50. Drainage Feasibility

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