Managing Managing Greenhouse Greenhouse

NutritionNutritionPaul A. Thomas and Bodie V. Paul A. Thomas and Bodie V.

Pennisi Pennisi Extension Horticulture Specialists Extension Horticulture Specialists

- Floriculture- FloricultureThe University of GeorgiaThe University of Georgia

Modern Modern ProductionProduction

Modern Modern ProductionProduction

Growers Growers should should

NOT NOT have have

nutritionnutritional al

problemproblemss

Why do we still have Why do we still have problems?problems?

Focus on solving problemsFocus on solving problems

Need to shift focus to Need to shift focus to PREVENTING problemsPREVENTING problems

What to What to Look ForLook For

Things that will impact plant nutritionThings that will impact plant nutrition Chemical characteristicsChemical characteristics

pH - water, fertilizer solutionpH - water, fertilizer solution EC - water, fertilizer solutionEC - water, fertilizer solution alkalinity - water, fertilizer solutionalkalinity - water, fertilizer solution

Nutritional valueNutritional value macronutrients, micronutriensmacronutrients, micronutriens

Non-nutritional elements – possible toxicitiesNon-nutritional elements – possible toxicities Na, Cl, F, AlNa, Cl, F, Al

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

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

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

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

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

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

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

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

6.0

6.5

7.0

7.5

0% 15% 35% 55%

Poinsettia Crop 10 Weeks After PlantingPoinsettia Crop 10 Weeks After Planting(adopted from (adopted from Greenhouse GrowerGreenhouse Grower, January 2001, p.72), January 2001, p.72)

Leaching FractionLeaching Fraction

Med

ia p

HM

edia

pH

The more water applied to the crop, the greater The more water applied to the crop, the greater effect high alkalinity water will have on media pH.effect high alkalinity water will have on media pH.

Initial media pH = 6.0Initial media pH = 6.0Water alkalinity = 320 ppm CaCOWater alkalinity = 320 ppm CaCO33

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

Dealing With Dealing With High And Low High And Low

Water Water AlkalinityAlkalinity

Dealing With Dealing With High And Low High And Low

Water Water AlkalinityAlkalinity

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

If acid injection required, use the Alkalinity If acid injection required, use the Alkalinity Calculator found on:Calculator found on:

www.ces.ncsu.edu/depts/hort/floriculture/www.ces.ncsu.edu/depts/hort/floriculture/software/software/

Correcting High AlkalinityCorrecting High AlkalinityCorrecting High AlkalinityCorrecting High Alkalinity

Most commonly used acids: sulfuric, Most commonly used acids: sulfuric, phosphoric, nitric.phosphoric, nitric.

Need to consider the extra phosphorus (P), Need to consider the extra phosphorus (P), nitrogen (N), or sulfur (S) in the acid when nitrogen (N), or sulfur (S) in the acid when selecting fertilizer.selecting fertilizer.

3.4 fl oz of 85% phosphoric acid/100 gal 3.4 fl oz of 85% phosphoric acid/100 gal adds 122 ppm P to the irrigation wateradds 122 ppm P to the irrigation water

If acid is changed, nutritional program needs If acid is changed, nutritional program needs to be re-evaluated.to be re-evaluated.

Correcting High AlkalinityCorrecting High AlkalinityCorrecting High AlkalinityCorrecting High Alkalinity

Other FactorsOther Factors

SalinitySalinitySalinitySalinity

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

Managing High Salinity in Managing High Salinity in Water SupplyWater Supply

Managing High Salinity in Managing High Salinity in Water SupplyWater Supply

DiluteDilute with collected rainwater or with collected rainwater or other low salinity water sourcesother low salinity water sources

Use reverse osmosis water Use reverse osmosis water treatment, particularly for misting treatment, particularly for misting cuttings, irrigating seedlings, and cuttings, irrigating seedlings, and salt-sensitive cropssalt-sensitive crops

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 …

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.

Commercial Commercial LabLab

1.1. Need test for alkalinityNeed test for alkalinity2.2. Need Need Fluorine (F) and/or Chlorine Fluorine (F) and/or Chlorine

(Cl) if high levels are suspected.(Cl) if high levels are suspected.

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 & Charts for recording pH & ECEC

Guidelines for cropsGuidelines for crops

Procedures to keep on trackProcedures to keep on track

Measuring Measuring TechniqueTechnique

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

Monitoring Monitoring QuestionsQuestions

Number of samples?Number of samples?

How often?How often?

Options?Options?

How to How to MonitorMonitor

Sample plants with different Sample plants with different requirements separatelyrequirements separately

pH: acidic vs basicpH: acidic vs basic EC: high vs lowEC: high vs low

Randomly select plantsRandomly select plants

Select plants from interior Select plants from interior of benchof bench

Monitoring: the Monitoring: the Key ...Key ...

Have a manageable planHave a manageable plan

Consider monitor and Consider monitor and managing to be your insurance managing to be your insurance policypolicy

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

High pH Action High pH Action StepsSteps

Acidify water to pH of 5.8Acidify water to pH of 5.8

Switch from NOSwitch from NO33-- to NH to NH44

++

Apply an iron sulfate drenchApply an iron sulfate drench 3 lb per 100 gallons3 lb per 100 gallons

mist solution off of foliagemist solution off of foliage

Acidify water to pH of 5.1Acidify water to pH of 5.1

Low pH Action Low pH Action StepsSteps

Stop neutralizing alkalinity in waterStop neutralizing alkalinity in water

Switch from NHSwitch from NH44++ to NO to NO33

--

Apply flowable limestone products:Apply flowable limestone products:

start with 1 quart per 100 start with 1 quart per 100

gallonsgallons

mist solution off of foliagemist solution off of foliage

Monitoring Monitoring ECEC

Set target EC ranges for Set target EC ranges for crop being growncrop being grown

Account for growth stagesAccount for growth stages Establishment, active Establishment, active growth, and bloomgrowth, and bloom

Set upper and lower rangesSet upper and lower ranges

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

PourThru PourThru EC’sEC’s

Crops vary in requirementsCrops vary in requirements Low: 1.0 - 2.6 mS/cmLow: 1.0 - 2.6 mS/cm

begonia, cineraria, begonia, cineraria, impatiensimpatiens

Moderate: 2.0 - 3.5 mS/cmModerate: 2.0 - 3.5 mS/cm Easter lily, geranium, kaleEaster lily, geranium, kale

Heavy: 2.6 - 4.6 mS/cmHeavy: 2.6 - 4.6 mS/cm chrysanthemum, chrysanthemum, poinsettiapoinsettia

High EC Action High EC Action StepsSteps

Decrease fertilization rateDecrease fertilization rate

Decrease fertilization frequencyDecrease fertilization frequency

LeachLeach

Low EC Action Low EC Action StepsSteps

Increase fertilization rateIncrease fertilization rate

Increase fertilization Increase fertilization

frequencyfrequency

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

Species Effect Species Effect on pHon pH

Marigold (African)Marigold (African)

pHpHStarting pHStarting pH

SpeciesSpecies

88

77

66

55

44

PansyPansy

VincaVincaZinniaZinnia

CelosiaCelosiaBegoniaBegonia

DianthusDianthusTomatoTomato

The Four Most The Four Most Common MistakesCommon Mistakes

1.1. Adoption of a single-fertilizer Adoption of a single-fertilizer formula for a given crop - formula for a given crop - Sticking to 20-20-20Sticking to 20-20-20

2.2. Trusting the fertilizer injectorTrusting the fertilizer injector

3.3. Not testing soil frequentlyNot testing soil frequently

4.4. Not testing the irrigation waterNot testing the irrigation water

5.5. Not performing foliar analysis Not performing foliar analysis mid-crop.mid-crop.

Pre-test irrigation water and media before Pre-test irrigation water and media before planting.planting.

Stock up on pH-adjusting chemicals and Stock up on pH-adjusting chemicals and basic fertilizers.basic fertilizers.

Use a water test analysis to select the Use a water test analysis to select the fertilizer and decide whether to acidify fertilizer and decide whether to acidify irrigation water.irrigation water.

Set up a pH, EC and nutrient monitoring Set up a pH, EC and nutrient monitoring program. program.

Testing The Testing The Foliage …Foliage …