Nutrition Management: Nutrition What do we monitor? Management

1/24/2012

1

Nutrition

Management

John Freeborn

Virginia Tech Floriculture

Nutrition Management:

What do we monitor?

Why do we monitor?

How do we monitor?

Pour thru technique for monitoring

Nutrition Management:

Monitoring pH and the EC of the substrate

Nutrition Management:

Monitoring pH and the EC of the substrate

pH—Concentration of Hydrogen Ions

Based on a 14 point scale

Scale is logarithmic (10x per number)

Controls nutrient availability

pH: pH:

C. Jones and J. Jacobsen, 2001, Plant Nutrition and Soil Fertility, Montana State University

Extension Service. Document can be downloaded from:

http://www.montana.edu/wwwpb/pubs/mt4449.html.

1/24/2012

2

pH Ranges:

Figure 2. Sugge sted substrate pH ranges for spe cific gre enhouse crops grown in soilless substrate .

Species

pH Range

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

Easter Lily

Celosia

Dianthus

Geranium

Marigold, African

Hydrangea (Pink)

General Crops

Pansy

Petunia

Salvia

Snapdragon

Vinca

Hydrangea (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

(tak e corrective steps so the pH moves back into the

acceptable range)

Target Range

Nutrition Management:

Monitoring Electrical Conductivity (EC)

Concentration of dissolved salts in water

Units are typically mS/cm

EC Values from a Pour Thru:

EC Value (mS/cm) Indication

0.0 to 1.0 Very Low

1.0 to 2.6 Low

2.6 to 4.6 Normal

4.6 to 6.5 High

6. 5 + Very High

EC Ranges:

Lower Fertility Moderate Fertility Higher Fertility

0.75 – 2.00 2.01 – 3.5 3.6 – 5.0

Asclepias

Azalea

Caladium

Calla Lily

Coleus

Cuttings while rooting

Cyclamen

Gloxinia

Impatiens

Pansy

Alyssum

Carnation

Cleome

Dahlia

Dianthus

Petunia

Phlox

Rose

Tomato

Chrysanthemum

Penstemon x ‘Sour

Grapes’

Poinsettia

Salvia nemerosa

Nutrition Management:

Importance of pH and EC in crop

development

Fertilization (CLF) is a frequent opportunity

to help (or harm)

Varies by crop, season, and time

Nutrition Management:

Importance of pH and

EC in crop

development

Fertilization (CLF) is a

frequent opportunity

to help (or harm)

1/24/2012

3

Nutrition Management:

Now, how do we monitor pH and EC?

Monitoring Equipment:

Hanna Meter

Pour Thru Technique

pH, EC and TDS

$200.00

Replaceable

electrode

Monitoring Equipment:

Direct Stick Probes

$ 365.00

Replaceable probe

Test directly in media

Monitoring Equipment:

Others

Monitoring pH and EC:

How?

Pour Thru technique

Direct stick probes

Where?

At the hose end

Substrate (pots or trays)

At the Hose End:

Check monthly

Examine injector(s)

1/24/2012

4

At the Hose End:

Check monthly

Examine injector(s)

Injection rate

Final product

Volume

EC (pH?)

Verify on Fertilizer Bag

Example: Peter’s Professional 20-10-20 GP

200 ppm N

concentration (desired)

Injector ratio of 1:100

Target EC in final

solution = 1.32 mS/cm

Peter’s Professional 20-10-20 GP

Check the Label

Ounces of Peters Professional 20-10-20

Per Gallon of Concentration

ppm Injector Ratio E.C.

Nitrogen 1:15 1:100 1:128 1:200 mS/cm

50 0.50 3.38 4.32 6.75 0.33

100 1.00 6.75 8.64 13.50 0.66

150 1.50 10.13 12.96 20.25 1.00

200 2.00 13.50 17.28 27.00 1.32

250 2.50 16.88 21.60 33.75 1.65

300 3.00 20.25 25.92 40.50 1.98

350 3.50 23.63 30.24 47.25 2.31

400 4.00 27.00 34.56 54.00 2.64

Substrate Monitoring:

Pour Thru Technique

Pour Thru Technique:

Water normally

Wait patiently for 60 minutes

Put saucer under pot or cell pack

Calibrate probe for pH and EC

Water with known volume of distilled water

Pour Thru Technique:

“Trade” gallon: 100 ml

Full gallon+: 125-150 ml

Quart: 75 ml

1/24/2012

5

Pour Thru Technique:

Water normally

Wait patiently for 60 minutes

Put saucer under pot or cell pack

Calibrate probe for pH and EC

Water with known volume of distilled water

Collect leachate with saucer

Sample leachate

Record EC and pH

Tips:

Be consistent with irrigation

Using distilled water and rinsing probe

between measurements

Do at least five different pots from the

same crop and chart

Testing either weekly or biweekly

Do not allow electrode to dry out

Questions?