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