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

The Goal Is To The Goal Is To Achieve A Achieve A

Stable Medium Stable Medium pH Over TimepH Over Time

The Goal Is To The Goal Is To Achieve A Achieve A

Stable Medium Stable Medium pH Over TimepH Over Time

Plant Growth CyclePlant Growth Cycle

Poinsettia Growth Over Time

0

5

10

15

20

0 3 6 9 12 15

Weeks After Potting

Plan

t Dry

Wt (

g) Active GrowthActive GrowthEst

ab

lish

men

tEst

ab

lish

men

t

Matu

reM

atu

re

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

pH DriftpH Drift

Alkaline WaterAlkaline Water

pHpH

NHNH44++ fertilizers fertilizers

TimeTime

8.58.58.08.07.57.57.07.06.56.56.06.05.55.55.05.04.54.5

““Optimum” RangeOptimum” Range

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” pHNote: Alkalinity “controls” pHMust 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

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

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

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

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

Action Steps To Correct High AlkalinityAction Steps To Correct High AlkalinityAction Steps To Correct High AlkalinityAction Steps To Correct High Alkalinity

reverse osmosis

acid injection

acid fertilizer and/or

none

less lime

Alkalinity Alkalinity (ppm) (ppm)

bicarbonatebicarbonate

480480

180180

120120

SalinitySalinitySalinity is measured by Salinity is measured by

Electro-conductivity Electro-conductivity

SalinitySalinitySalinity is measured by Salinity is measured by

Electro-conductivity Electro-conductivity

Total Dissolved Salts (TDS) – all salts Total Dissolved Salts (TDS) – all salts present in the water (1 mMho/cm=640 ppm)present in the water (1 mMho/cm=640 ppm) less than 0.75 less than 0.75 mMhomMho /cm for plugs /cm for plugs less than 1.0 less than 1.0 mMhomMho /cm for other /cm for other

greenhouse cropsgreenhouse crops less than 2.0 less than 2.0 mMhomMho /cm for other nursery /cm for other nursery

cropscrops

Testing The Testing The Soil Solution !Soil Solution !

Simple technique for Simple technique for measuring pH and ECmeasuring pH and EC

Charts for recording pH & ECCharts for recording pH & EC

Guidelines for cropsGuidelines for crops

Procedures to keep on trackProcedures to keep on track

Pour Thru Pour Thru MethodMethod

6 or 8-inch saucers are adequate for 6 or 8-inch saucers are adequate for collecting the leachatecollecting the leachate

Distilled Water Distilled Water VolumesVolumes

4 inch4 inch5 inch5 inch6 inch6 inch6.5 inch6.5 inch1 Qt1 Qt4 Qt4 Qt12 Qt12 Qt

757575757575

1001007575

150150350350

2.52.52.52.52.52.53.53.52.52.55.05.0

12.012.0

Pot SizePot Size mlml ozoz

Flats: Use 50 ml Distilled Flats: Use 50 ml Distilled WaterWater

EC EC ComparisonsComparisons

0 to 0.30 to 0.3

0.3 to 0.80.3 to 0.8

0.8 to 1.30.8 to 1.3

1.3 to 1.81.3 to 1.8

1.8 to 2.31.8 to 2.3

> 2.3> 2.3

1:21:2 SMESME PourThruPourThruIndicationIndication

0 to 0.80 to 0.8

0.8 to 2.00.8 to 2.0

2.0 to 3.52.0 to 3.5

3.5 to 5.03.5 to 5.0

5.0 to 6.05.0 to 6.0

> 6.0> 6.0

0 to 1.00 to 1.0

1.0 to 2.61.0 to 2.6

2.6 to 4.62.6 to 4.6

4.6 to 6.54.6 to 6.5

6.6 to 7.86.6 to 7.8

> 7.8> 7.8

Very LowVery Low

LowLow

NormalNormal

HighHigh

Very HighVery High

ExtremeExtreme

Initial Initial ECEC

0

0.5

1

1.5

2

2.5

3

1 2 3

Irrigations

DaysHours

Crop pH RangesCrop pH RangesFigure 2. Suggested substrate pH ranges for specific greenhouse crops grown in soilless substrate.

Species

pH Range4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7.0

Easter Lily

CelosiaDianthusGeraniumMarigold, African

Hydrangea (Pink)

General CropsPansyPetuniaSalviaSnapdragonVincaHydrangea (Blue)

Azalea

4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7.0

M&M KeyManagement Decision Range(take corrective steps so the pH moves back into theacceptable range)

Target Range

4.2

4.4

8.0

7.6

7.2

6.8

6.4

6.0

5.6

5.2

4.8

Week

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Crop _____________________________ Target pH Range _______

Starting Date (week 0) ________ Upper pH Decision Range_____

Ending Date ___________ Lower pH Decision Range_____

4.6

5.8

5.0

5.4

6.2

6.6

7.0

7.4

7.8

4.0

pH

Geraniums (6” pinched)

1/28

5/01

6.0 to 6.6

6.6 to 6.8

5.8 to 6.0