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Know Y our W ater Source

Know Y our W ater Source. Paul A. Thomas Extension Horticulture Specialist - Floriculture The University of Georgia. Where Does The Water Come From ?. Examples of Variation in Groundwater Quality. Well # 1. Well # 2. Well # 3. Soil Zone. Sand and Gravel Aquifer.

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Know Y our W ater Source

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  1. Know Your Water Source Paul A. Thomas Extension Horticulture Specialist - Floriculture The University of Georgia

  2. Where Does The Water Come From ?

  3. Examples of Variation in Groundwater Quality Well # 1 Well # 2 Well # 3 Soil Zone Sand and Gravel Aquifer Limestone or Granite Aquifer Sandstone Aquifer

  4. Irrigation Water Alkalinity concentrations (ppm CaCO3) from Florida 25 20 15 10 5 0 Frequency % <40 40–80 80-20 120-160 160-200 200-240 240-280 280-320 320-360 360-400 >400

  5. Testing The Waters …

  6. Hardness • Calcium and magnesium are the major contributors • “hard water” has a high Ca and/or Mg • “hard water” is generally associated with high alkalinity • can have hard water and low alkalinity – water high in CaCl2 and/orMgCl2

  7. Alkalinity CaMg(CO3)2 Ca2+ + Mg2+ + 2CO32- Dolomitic limestone Hardness Hardness and Alkalinity Generally Go Hand-In-Hand but They Are NOT One and the Same You Can Use the Water Hardness to Estimate Its Alkalinity

  8. Alkalinity • A measure of water’s ability to neutralize acids – a buffering ability • Mostly carbonates and bicarbonates – associated with Ca and Mg (limestone) • May cause pH to rise in media over time, especially in small containers Note: Alkalinity “controls” pH Must know alkalinity to manage pH

  9. Alkalinity • Expressed in ppm, mg/L, meq/L • Expressed as CaCO3 or HCO3- • Irrigation water should have an alkalinity of less than 100ppm; if higher than 150 ppm, acidification is needed

  10. Hardness • If you have hard water: • check Ca and Mg concentrations • if high use less lime • monitor pH ! • check Ca : Mg ratio • ideal ratio is 3:1 if expressed in meq/L • ideal ratio is 5:1 if expressed in ppm

  11. Substrate Acidity 2CO32- + 2H + H2CO3 Alkalinity H2O + CO2 Both the alkalinity and the acidity are neutralized

  12. pH • pH affects the solubility of fertilizers, and the efficacy of pesticides and growth regulators. • the higher the water pH the less soluble these materials are

  13. The Effect of Water Alkalinity on Media pH and Acid Requirement Sample A Sample B pH = 9 pH = 7 Alk = 50 ppm Alk = 300 ppm Increases growing medium pH Little or no effect on the growing medium pH One drop of acid to get pH 6 Ten drops of acid to get pH 6

  14. Testing Water Quality In-House • Range 0-8 meq/L (0-400 ppm alkalinity expressed as CaCO3) • Accuracy  0.4 meq/L or better • Kits from $30 for 100 tests to $155 for 100 tests.

  15. Alkalinity Terms mg/liter or ppm CaCO3 of alkalinity mg/liter or ppm bicarbonate Milliequivalents alkalinity 1 2 3 4 5 50 100 150 200 250 60 122 183 244 305

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