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Soil Science

Soil Science. Holton Agriculture Education Department. Why Study Soil Science?. Land is a Natural Resource It provides raw materials Enables us to produce food & fiber Stores & collects water for use Is the primary source of habitat for wildlife. Soil Classification . Capability Classes

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Soil Science

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  1. Soil Science Holton Agriculture Education Department

  2. Why Study Soil Science? • Land is a Natural Resource • It provides raw materials • Enables us to produce food & fiber • Stores & collects water for use • Is the primary source of habitat for wildlife

  3. Soil Classification • Capability Classes • Developed by the USDA • Identifies land by its’ characteristics • Class I-IV= Can be used for cropland • Class V-VII= Non-cropland agricultural use • Class VIII= Used for wildlife & recreation

  4. Soil Profile- A group of soil layers- from top to bottom • Top layer- often decaying organic material • Topsoil (A Horizon)- Most developed part of a soil • Sub-soil (B Horizon)- Layer of soil below the layer that is usually tilled • Parent Material (C Horizon)- Weathered material that often restricts root development

  5. Soil Factors • Used to Determine Land Classification • Texture • Surface • Subsurface • Depth of Soil • Slope • Erosion

  6. Determined by the amount of each soil separate within a given sample Soil Separates Sand Silt Clay Soil Texture

  7. Soil Separates • Sand • .002 to .08 inches • Feels gritty • Silt • .00008 to .002 inches • Feels smooth when wet • Clay • Less than .00008 inch • Feels sticky when wet

  8. Soil Texture • Is broken into five categories • Coarse- over 70% sand • Moderately Coarse- over 50% sand • Medium • Moderately Fine- 20% to 40% clay • Fine- at least 40% clay

  9. Depth of Soil • The total thickness of material available for plant root growth • “The thickness above any layer which restricts root development.” • Very important in locating buildings, crop fields, ponds, and sewage systems.

  10. Depth of Soil • Deep- more than 40 inches • Moderately Deep- 20 to 40 inches • Shallow- 10 to 20 inches • Very Shallow- less than 10 inches

  11. Slope • Refers to the steepness of a given area of land. • Affects the management and use of the land. • Is directly related to the hazard of erosion. • As slope increases, agricultural suitability decreases.

  12. Slope • Determined by the rise or fall of the land from one point to another point 100 feet away. • Simple equation is: Rise/Run=%Slope • 4 Feet / 100 Feet = 4% Slope 4 feet 100 Feet

  13. Classes of Slope • Nearly Level- Less than 1% • Gently Sloping- 1% to 3% • Moderately Sloping- 3% to 5% • Strongly Sloping- 5% to 8% • Steep- 8% to 15% • Very Steep- Greater than 15%

  14. Erosion • Process that causes the loss of soil by the action of water or wind. • The three types of erosion are: • Sheet- Results from the splash of rain. • Rill- Small channels cut into soil by running water- are easily smoothed by tillage. • Gully-Caused by concentrated running water cutting deep into the soil.

  15. Erosion • Process that removes the finer, more fertile soil materials. • Can be controlled by: • Conservation tillage • No-till • Reduced till • Leaving Crop Residues • Contour Tillage • Terracing • Vegetative Waterways

  16. GulliesAt least 6 inches deep and 1 foot wide. • Crossable gullies- Can be crossed at a regular speed with normal farm equipment in operation. • Uncrossable gullies- Can not be crossed at a regular speed with normal farm equipment in operation. • Frequent gullies- Less than 100 feet apart. • Occasional gullies- Over 100 feet apart.

  17. Determined by: Subtracting the current top soil depth from the original top soil depth. Dividing the difference by the original depth. Converting to a percentage. Tells the % of soil lost. Original Depth- 25 inches Current Depth- 20 inches Erosion 25 – 20 = 5 inches 5 / 25 = .20 .20 = 20% Erosion

  18. Levels of Erosion • None to slight- Less than 25% and no gullies. • Moderate- 25% to 75%. May have small, occasional, crossable gullies. • Severe- Greater than 75%. May have frequent crossable gullies or occasional uncrossable gullies. • Very Severe- Greater than 75%. Has frequent uncrossable gullies.

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