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THE DIRT ON SOIL

THE DIRT ON SOIL. The unknown ecosystem. A recipe for soil. Start with rocks and minerals Weather into small pieces Add organic materials (humus) Add water and air. Soil forms by weathering (minerals) and decomposition (humus). Be patient!.

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THE DIRT ON SOIL

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  1. THE DIRT ON SOIL The unknown ecosystem

  2. A recipe for soil • Start with rocks and minerals • Weather into small pieces • Add organic materials (humus) • Add water and air

  3. Soil forms by weathering (minerals) and decomposition (humus)

  4. Be patient! • It takes 100 to 100,000 years to form one meter of soil • Faster in warmer climates

  5. Soil Parts • Mineral (weathered rock) = 45% • Air = 25% • Water = 25% • Organic matter (humus) = 5%

  6. WHICH IS LARGER? • The number of organisms in one shovelful of soil • The number of humans on earth

  7. SOIL CREATURES • More in one shovelful than all the humans that have ever lived on earth • Many don’t even have names yet

  8. HUMUS • Dark organic matter from decomposed plants and animals • Soil organisms feed on it • Absorbs and holds water

  9. SOIL DECOMPOSERS: BACTERIA • 1000 fit on the head of a pin • Divide to reproduce every 20 minutes

  10. BEETLE MITES • Arachnids • No eyes (it’s dark in the soil) • Eat only fungus

  11. NEMATODES • Also called round worms • Only 1 mm long • Some eat bacteria, some eat detritus, some eat fungus

  12. EARTHWORMS • Live 3 to 6 years • Eat detritus, also swallow soil • Add bacteria back to soil

  13. SOIL TEXTURE • Soil has different textures • The texture is caused by the size of the mineral particles

  14. Sand • Sandy soil drains quickly so roots can penetrate. Too much sand in a soil does not hold enough water and nutrients for most plants. • Does not shrink or swell so it makes a good foundation for buildings. • Sand – Between 0.06 – 2.0 mm in size

  15. Silt • Silt allows for air to circulate but still retains some water. Silty soils do not usually hold enough water for most plants. • Silt – Between 0.002 - 0.05 mm in size

  16. Clay • Water clings to tiny particles holding larger soil particles together forming clumps called aggregates • Aggregates like gravel provide drainage channels for water. Water will not drain in soils with a lot of clay. • < 0.002 mm in size • Clay is a poor material to build on because it shrinks and swells with water. • Clay is easily compacted crushing air and water pore space. Plants root cannot penetrate through dense clay soils.

  17. Loam • A soil with a mixture of sand, silt and clay. It is the best type of soil for most crops

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