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

Where Does The Water Come From ?

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

Frequency % Irrigation Water Alkalinity concentrations (ppm CaCO 3 ) from Florida <40 40– >400

Testing The Waters …

 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 CaCl 2 and/or MgCl 2 HardnessHardness

CaMg(CO 3 ) 2 Dolomitic limestone Ca 2+ + Mg CO 3 2- Hardness Alkalinity 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

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

Expressed in ppm, mg/L, meq/L Expressed in ppm, mg/L, meq/L Expressed as CaCO 3 or HCO 3 - Expressed as CaCO 3 or HCO 3 - AlkalinityAlkalinity Irrigation water should have an alkalinity of less than 100ppm; if higher than 150 ppm, acidification is needed Irrigation water should have an alkalinity of less than 100ppm; if higher than 150 ppm, acidification is needed

 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 HardnessHardness

H 2 CO 3 2CO H + H 2 O + CO 2 Substrate Acidity Alkalinity Both the alkalinity and the acidity are neutralized

 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 pHpH

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

Testing Water Quality In-House  Range 0-8 meq/L (0-400 ppm alkalinity expressed as CaCO 3 )  Accuracy  0.4 meq/L or better  Kits from $30 for 100 tests to $155 for 100 tests. $155 for 100 tests.

Alkalinity Terms Milliequivalents alkalinity mg/liter or ppm CaCO 3 of alkalinity mg/liter or ppm bicarbonate