Know Your Know Your Water SourceWater Source
Paul A. Thomas Paul A. Thomas Extension Horticulture Specialist Extension Horticulture Specialist
- Floriculture- FloricultureThe University of GeorgiaThe University of Georgia
Where Does Where Does The Water The Water
Come From ?Come From ?
Soil ZoneSoil ZoneSand and Gravel Sand and Gravel
AquiferAquifer
Limestone or Limestone or Granite AquiferGranite Aquifer
Sandstone Sandstone AquiferAquifer
Examples of Variation in Groundwater Examples of Variation in Groundwater QualityQuality
Examples of Variation in Groundwater Examples of Variation in Groundwater QualityQuality
Well # 1 Well # 2 Well # 3
25
20
15
10
5
0
Fre
qu
ency
%
Irrigation Water Alkalinity concentrations Irrigation Water Alkalinity concentrations (ppm CaCO(ppm CaCO33) from Florida) from Florida
<40
40–8
0
80-2
0
120-
160
160-
200
200-
240
240-
280
280-
320
320-
360
360-
400
>40
0
Testing The Testing The Waters …Waters …
Calcium and magnesium are the major Calcium and magnesium are the major contributorscontributors
“ “hard water” has a high Ca and/or Mghard water” has a high Ca and/or Mg “ “hard water” is hard water” is generallygenerally associated associated with high alkalinitywith high alkalinity can have hard water and low can have hard water and low alkalinity – water high in CaClalkalinity – water high in CaCl2 2 and/orand/or
MgClMgCl22
HardnessHardnessHardnessHardness
CaMg(COCaMg(CO33))22
Dolomitic Dolomitic
limestonelimestone
CaCa2+2+ + Mg + Mg2+2+ + 2CO + 2CO332-2-
HardnessHardness
AlkalinityAlkalinity
Hardness and Alkalinity Generally Hardness and Alkalinity Generally Go Hand-In-Hand but They Are Go Hand-In-Hand but They Are
NOT One and the SameNOT One and the Same
You Can Use the Water Hardness You Can Use the Water Hardness to Estimate Its Alkalinityto Estimate Its Alkalinity
A measure of water’s ability to A measure of water’s ability to neutralize acids – a buffering abilityneutralize acids – a buffering ability
Mostly carbonates and Mostly carbonates and bicarbonates – associated with Ca bicarbonates – associated with Ca and Mg (limestone) and Mg (limestone)
May cause pH to rise in media May cause pH to rise in media over time, especially in small over time, especially in small containerscontainers
AlkalinityAlkalinityAlkalinityAlkalinity
Note: Alkalinity “controls” Note: Alkalinity “controls” pHpH
Must know alkalinity to Must know alkalinity to manage pHmanage pH
Expressed in ppm, mg/L, meq/LExpressed in ppm, mg/L, meq/L
Expressed as CaCOExpressed as CaCO3 3 or HCOor HCO33--
AlkalinityAlkalinityAlkalinityAlkalinity
Irrigation water should have Irrigation water should have an alkalinity of less than 100ppm; an alkalinity of less than 100ppm; if higher than 150 ppm, if higher than 150 ppm, acidification is neededacidification is needed
If you have hard water:If you have hard water: check Ca and Mg concentrationscheck Ca and Mg concentrations
if high use less limeif high use less lime monitor pH !monitor pH !
check Ca : Mg ratiocheck Ca : Mg ratio ideal ratio is 3:1 if expressed in meq/Lideal ratio is 3:1 if expressed in meq/L ideal ratio is 5:1 if expressed in ppmideal ratio is 5:1 if expressed in ppm
HardnessHardnessHardnessHardness
HH22COCO332CO2CO332- 2- + 2H + 2H ++
HH22O + COO + CO22
Substrate Substrate AcidityAcidity
AlkalinityAlkalinity
Both the alkalinity and Both the alkalinity and the acidity are neutralizedthe acidity are neutralized
pH affects the solubility of fertilizers, pH affects the solubility of fertilizers, and the efficacy of pesticides and and the efficacy of pesticides and growth regulators.growth regulators.
the higher the water pH the less the higher the water pH the less soluble these materials aresoluble these materials are
pH pH pH pH
Sample ASample A Sample BSample B
pH = 9pH = 9 pH = 7pH = 7
One drop of acid to get pH 6One drop of acid to get pH 6 Ten drops of acid to get pH 6Ten drops of acid to get pH 6
The Effect of Water Alkalinity on Media The Effect of Water Alkalinity on Media pH and Acid RequirementpH and Acid Requirement
The Effect of Water Alkalinity on Media The Effect of Water Alkalinity on Media pH and Acid RequirementpH and Acid Requirement
Little or no effect on the Little or no effect on the growing medium pHgrowing medium pH
Increases growing medium Increases growing medium pHpH
Alk = 50 Alk = 50 ppmppm Alk = 300 Alk = 300 ppmppm
Testing Water Quality Testing Water Quality In-HouseIn-HouseTesting Water Quality Testing Water Quality In-HouseIn-House
Range 0-8 meq/L (0-400 ppm Range 0-8 meq/L (0-400 ppm alkalinity expressed as CaCOalkalinity expressed as CaCO33))
Accuracy Accuracy 0.4 meq/L or better 0.4 meq/L or better Kits from $30 for 100 tests toKits from $30 for 100 tests to
$155 for 100 tests. $155 for 100 tests.
Alkalinity TermsAlkalinity TermsAlkalinity TermsAlkalinity Terms
Milliequivalents Milliequivalents alkalinity alkalinity
mg/liter or mg/liter or ppm CaCOppm CaCO33 of alkalinity of alkalinity
11
22
33
44
55
mg/liter or mg/liter or ppm ppm
bicarbonate bicarbonate
5050
100100
150150
200200
250250
6060
122122
183183
244244
305305
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