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SOIL CHEMISTRY

SOIL CHEMISTRY

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SOIL CHEMISTRY

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  1. SOIL CHEMISTRY

  2. SOIL pH A measure of the degree to which the soil is Acidic or Basic; also known as . . . Soil Reaction

  3. SOIL pH Technically: expressed as the negative logarithm of the hydrogen ion (H+) concentration

  4. SOIL pH At pH 7: - neutral pH - indicates H+ concentration of . . . 10-7 mol/L

  5. SOIL pH Since the product of normalities of H+ and OH- ions is always 10-14, OH- is also 10-7 mol/L mathematically . . . (10-7)(10-7) = 10-14

  6. SOIL pH therefore . . . at neutral pH (pH 7 on a scale from 0 to 14) amount of H+ ions = amount of OH- ions solution is neither acidic nor basic

  7. SOIL pH Most agricultural soils pH range from 4 to 9 . . . common productive agriculture soils fall between pH 5 to 8

  8. SOIL pH 2 factors affecting pH are: 1) Amount of precipitation 2) Type of vegetation

  9. SOIL pH AMOUNT OF PRECIPITATION – HUMID AREAS (heavy rainfall)  ACID SOILS Ca+, Mg+, and Na+ are leached downward and replaced by H+ ions

  10. SOIL pH TYPE OF VEGETATION – Vegetation affects pH over period of years: grasslands – higher pH forests – lower pH

  11. SOIL pH The most critical effects of soil pH are indirect . . . the availability (unavailability) of certain nutrients is greatly influenced by soil pH

  12. SOIL pH Nutrients UNAVAILABLE at higher pH: Cu – Copper Fe – Iron Mn – Manganese Zn – Zinc

  13. SOIL pH additionally . . . nitrogen-fixing bacteria associated with legumes are seriously hindered in acid soils Critical with beans and peas

  14. SOIL pH ADJUSTING SOIL pH - Crops vary considerably regarding soil pH preferences

  15. SOIL pH AZALEA BLUEBERRY RHODODENDRON ACID SOILS

  16. SOIL pH Mildly Acid Soils: Wheat Corn Soybean Apple Tomato

  17. SOIL pH Neutral to Slightly Acid Soils: Alfalfa Lettuce Muskmelon

  18. SOIL pH RAISING Soil pH: ADD LIME Factors to consider before applying - soil type - how much to raise the pH - fineness of lime - type of lime

  19. SOIL pH AMOUNT OF LIME NEEDED TO RAISE pH: Sandy Loam < Clay Loam WHY? Cation Exchange Capacity (CEC) of clay particles

  20. SOIL pH LOWERING Soil pH: AddSulfur - May be necessary for acid-loving crops - May also benefit potato production by reducing potato scab