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Soil Texture

Soil Texture. A Physical Property of Soil. Soil Texture: . The way the soil “feels” Depends on the percentages sand, silt, and clay in the soil These are the mineral particles in the soil Sand : the largest particles; 2.00 – 0.05 mm Silt : medium sized particles; 0.05 – 0.002 mm

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Soil Texture

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  1. Soil Texture A Physical Property of Soil

  2. Soil Texture: • The way the soil “feels” • Depends on the percentages sand, silt, and clay in the soil • These are the mineral particles in the soil • Sand: the largest particles; 2.00 – 0.05 mm • Silt: medium sized particles; 0.05 – 0.002 mm • Clay: the smallest sized particles; < 0.002 mm

  3. Soil Texture: Size Matters Relative Size Comparison of Soil Particles beach ball baseball dime Clay (feels sticky) Silt (feels floury) (< 0.002 mm, USDA) (0.05 - 0.002 mm, USDA) Sand (feels gritty) (2.00 - 0.05 mm, USDA)

  4. Assessing Soil Texture:"Quick and Dirty" Jar Method Clay: 1" 3" Total Sediment Silt: 1" Sand: 1" • Collect a 2-3 cup soil sample. • Let it dry-out; periodically "crumble" the sample. • Place 1 cup of the sample in a 1 quart glass jar. • Add 1 tsp. of Calgon Water Softener® or liquid detergent. • Add water; fill to about 1" from top of the jar. • Shake vigorously for 3 minutes. Set on flat surface. • Measure sediments: • 1 Minute: Sand • 1 Hour: Silt • 1 Day: Clay

  5. Clay Silty Clay Sandy Clay Clay Loam Silty Clay Loam Sandy Clay Loam Loam Silty Loam Sandy Loam Loamy Sand Silt Sand Soil Textural Triangle 100 0 10 90 20 80 30 70 % Silt 40 % Clay 60 50 50 60 40 70 Soil Textural Classifications 30 80 20 Our Soil: 33% Sand 33% Silt 33% Clay 90 10 100 0 0 100 90 80 70 60 50 40 30 20 10 % Sand

  6. Clay Silty Clay Sandy Clay Clay Loam Silty Clay Loam Sandy Clay Loam Loam Silty Loam Sandy Loam Loamy Sand Silt Sand Soil Textural Triangle 100 0 10 90 20 80 30 70 % Silt 40 % Clay 60 50 50 60 40 70 30 Loam 80 20 Loam: 40% Sand 33.1% Silt 26.9% Clay 90 10 100 0 0 100 90 80 70 60 50 40 30 20 10 % Sand

  7. Clay Silty Clay Sandy Clay Clay Loam Silty Clay Loam Sandy Clay Loam Loam Silty Loam Sandy Loam Loamy Sand Silt Sand Soil Textural Triangle 100 0 10 90 20 80 30 70 % Silt 40 % Clay 60 50 50 60 40 70 30 80 20 90 10 100 0 0 100 90 80 70 60 50 40 30 20 10 % Sand

  8. Loam Topsoil A: Subsoil B: Clay Parent Material C: Bedrock D: Texture: May Mimic Compaction WATER WATER Organic O: Then It Only Slowly Infiltrates The Soil Water May First Run Off Clay Soil Water Rapidly Infiltrates Loam Soil

  9. Soil Texture: A Few Points • What about Gypsum? • Gypsum = Calcium Sulfate: CaSO4 • Makes “salt soils” (sodic soils) less sticky, but it’s a chemical reaction! • Cannot improve clay soils = a physical problem • Sounds like what it is: gyp some • A Gypsum Reprieve: • An excellent source of calcium that does not affect soil pH • Used in place of Dolomitic Lime: CaMg(CO3)2

  10. Soil Texture Let’s Dig A Little Deeper

  11. Soil Texture and Water

  12. GRAVITATIONAL WATER 4 (SATURATION) 3 Inches of Water Per ft. of Soil 2 1 Sand Clay Sandy Loam Clay Loam Silt Loam Soil Texture Soil Texture and Water FIELD CAPACITY WATER AVAILABLE TO PLANTS PERMANENT WILTING POINT UNAVAILABLE WATER Clay Holds Onto More Water … Why?

  13. Water is Held on the Surface of Soil Particles Soil Particle Size & Water Volume The amount of water a particle holds is directly related to the particle’s Surface-to-Volume Ratio How Can We Increase the Surface-to-Volume Ratio?

  14. Increasing Total Surface Area • How do we increase the total surface area of this table? • We cut it into sections …

  15. Texture: Size Matters Clay has a greater surface-to-volume ratio = it has more total surface area to hold water A Sand Particle Clay Particles

  16. Biological Soil Properties:They Are Not Independent! Chemical Physical

  17. A Short Segway

  18. A Little Chemistry Lesson Please be Gentle

  19. - (+) A Chemistry Primer: The Atom Electron = negative charge It’s Electrifying!! Nucleus = positive charge This is a Hydrogen atom Electricity is the Movement of Electrons

  20. - - (+) A Chemistry Primer: • What happens when an atom has too many electrons? • It has a negative charge ( - ) • These atoms are called: Anions

  21. - - (+) A Chemistry Primer: • What happens when an atom doesn’t have enough electrons? • It has a positive charge (+) • These atoms are called: Cations

  22. Magnets Opposites Attract - - + + Likes Repel - + + - A Chemistry Primer: • What happens when an anion meets a cation? • Anions have a negative charge (-): • Chlorine: Cl- • Cations have a positive charge (+): • Sodium: Na+ • When they meet, they combine to become a molecule = a chemical compound: • NaCl (sodium chloride = salt)

  23. + + + + + + + + + + + + + + + + (+) (+) These orbits share one electron. This is a covalent bond - - - - - - - - - - - - - - - A Water Molecule: H2O + Hydrogen Hydrogen Water Is Bipolar - (+) Oxygen

  24. Magnets Opposites Attract - - + + Likes Repel - + + - Strange Properties of Water

  25. Strange Properties of Water Electrostatic Bond Water Water Water Water Water Water - - - - - + + + + + Water Water Water Water Water "Surface Tension" "Capillary Attraction"

  26. - - - - - - - - - - - - - - - - - - - - - - - - - - Clay Particles and Water Bipolar H2O: - + - - - - - - - - + + + + + + + + Water Water Water Water Water Water Water Water Water Clay Particle Clay particles have negatively charged sites on their surface Electrostatic Bonds

  27. GRAVITATIONAL WATER 4 (SATURATION) FIELD CAPACITY 3 Inches of Water Per ft. of Soil WATER AVAILABLE TO PLANTS 2 PERMANENT WILTING POINT 1 UNAVAILABLE WATER Sand Clay Sandy Loam Clay Loam Silt Loam Soil Texture Soil Texture and Water • Clay has a larger surface-to-volume ratio • Clay holds onto water with electrostatic bonds Why does clay hold onto more water than sand?

  28. What Does This All Mean to You? Soil Incompatibility!

  29. H2O H2O H2O Sand Over Clay: Dry Surface / Saturated Root Zone DRY Sand Wet Clay

  30. H2O H2O H2O Clay Over Sand: Perched Water Table Some Run-Off Wet Clay DRY Sand

  31. Water Sand Particles Mixing Sand with Clay Mixing Sand with Clay: Particle Infiltration Inhibits Water Drainage Water Water • Adding Sand: • At least 70% (by volume) to affect change without creating the “concrete” effect. • Means soil must be removed!

  32. Soil Texture: The Root Ball vs. the Surrounding Soil

  33. Solution: • Create a transition zone between extremely different particle sizes

  34. More About Clay Is Clay “Bad”?

  35. The Soil Test * To convert lb/A (pounds per acre) to ppm (parts per million), divide by 2. Example: 100 lb/A = 50 ppm

  36. WHAT IS Cationic Exchange Capacity (CEC) AND WHY IS IT IMPORTANT?

  37. CEC BUS The Chemistry of Clay Riding the CEC Bus H + K+ Ca++ K+ Mg++ H + K+ Mg2 H H + H + H H H - - Ca2 K K - - H - H + - - - - - H - - CEC Bus Passenger Seating H K Mg2 Ca2 H H - H + - H + K Clay Particle H = 16 (16 seats) = 6 (6 seats) = 2 (4 seats) = 2 (4 seats) - - - - H - K+ K - K+ H - H + - K+ - - H Clay particles are surrounded by negative charges - - This bus has 30 “seats” - - H - - K Ca2 K H H H Mg2 Ca++ Mg++ H + H + "Soil Solution"

  38. CEC BUS CEC BUS CEC BUS CEC BUS CEC BUS CEC BUS CEC BUS CEC BUS Cationic Exchange Capacity (CEC): • Measures Total CEC: All clay particles in the soil! • Like measuring the total number of seats on a whole fleet of buses Quadrillions of Seats!

  39. What Does CEC Mean to You? • The higher the CEC, the higher the soil’s capacity to hold onto nutrients … held against being washed through the soil by water • The lower the CEC, the faster the nutrients (fertilizer) are washed through the soil by water • Usually, the higher the CEC, the higher the clay content of the soil “Soil-less Media” Constant Fertilizer Applications Rain Gardens: Should You Use Sand? Sand: Almost No CEC

  40. Soil and Plant Adaptations Some plants are adapted to living in sandy soils Most did not evolve in the Midwest

  41. The Soil Test * To convert lb/A (pounds per acre) to ppm (parts per million), divide by 2. Example: 100 lb/A = 50 ppm

  42. WHAT IS pH? AND WHY IS IT IMPORTANT?

  43. pH Scale pH of some common substances pH 0 Battery acid 1 Stomach acid 2 Lemon juice Vinegar 3 Acid Orange juice 4 Tomatoes 5 Potatoes 6 Milk NEUTRAL 7 Blood (7.35 – 7.45) 8 Chlorine bleach 9 Base Baking soda 10 (Alkaline) Household ammonia 11 Soap solutions 12 Hair remover 13 Lye 14

  44. ARRGGGH! My head hurts! A Little More Chemistry

  45. (+) (+) (+) A Water Molecule: H2O The Water Molecule Plays a Critical Role with pH! Hydrogen Hydrogen Oxygen

  46. (+) What is pH? • It stands for: “potential Hydrogen” • It’s driven by the self-ionization of water: H2OH+ + OH- OH- Hydroxy Ion H+ Hydrogen Ion a

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