March 31, 2009

Electrical Conductivity (EC)

Posted in definisi tagged , , at 6:56 p03 by himproagro

Electrical Conductivity (EC)

Function:

Soluble salts refer to the total dissolved salts in the root substrate (medium) at any given time and is measured in terms of electrical conductivity (EC). All fertilizer materials contribute to the EC content of the root substrate, most commonly these are nitrates (NO3), ammonium (NH4), phosphates (PO4), potassium (K), calcium (Ca), magnesium (Mg), boron (B), iron (Fe), zinc (Zn), copper (Cu), sulfates (SO4), sodium (Na), bicarbonate (HCO3) and chlorides (Cl). Organic materials also contribute to the EC content after they have been changed from an insoluble to soluble form. Nitrogen and potassium are the fertilizer materials that most often contribute to the EC concentration of the root substrate. In some areas, high sodium in the irrigation water can also be a problem.

Deficiency:

At the opposite end of the spectrum, when the EC content of the root substrate is too low, plant growth is stunted from lack of fertilizer

Excess:

Excess salts accumulate when leaching during irrigation is insufficient, too much fertilizer is applied, or the irrigation water contains a high amount of dissolved elements. Excessively high EC readings are associated with poor plant growth. Plant symptoms often begin on the lower leaves as leaf chlorosis and progress to necrotic leaf tip margins. If the root substrate is allowed to dry down, plants may also exhibit wilting symptoms because of dieback of the root tips, which further inhibit water and fertilizer uptake. High EC has also been linked with the increased incidence of Pythium root rot.

Confirm your actual EC levels by conducting a routine root substrate (medium) test.

Monitoring and Management Strategy for Electrical Conductivity (EC) Fertilization Rate:

1.5 to 2.5 mS/cm. Optimal range is 25% to 50% lower with flood irrigation or reduced leaching fertilization programs.

Options:

Preplant:

Incorporation of fertilizer in the root substrate (medium) for a starter charge.

Continual Fertilization:

  1. Use a fertilizer that provides N. Examples include calcium nitrate (Ca(NO3)2) with potassium nitrate (KNO3), 20-10-20, 15-5-25, Excel® 15-5-15 Cal-Mag and others.
  2. If using calcium nitrate (Ca(NO3)2) and potassium nitrate (KNO3), remember to supply P, Mg, and micro-nutrients to the plants.
  3. If using 20-10-20 or 20-20-20, remember to supply Ca and Mg to the plants.

Corrective Fertilization:

Too High EC:

  1. Decrease the fertilization rate or the frequency of fertilization.
  2. Leaching will reduce the salts level. The root substrate should be irrigated normally, then followed immediately with another irrigation. After this, the root substrate should be allowed to dry to the usual stage, and if further leaching is required, a double-irrigation treatment can be repeated. Check the EC level again to make sure it is within the acceptable range.

Too Low EC:

Increase the fertilization rate or the frequency of fertilization. See target levels listed under nitrogen.

Electro – Conductivity (EC) or Conductivity Factor (cF) can be expressed as either millisiemens (mS), cF or parts per million (ppm).

Example: 1mS = 10cF = 700ppm.

The pH and Electro – Conductivity values specified here are given as a broad range. It should be noted that different seasons and climate will alter the needs of your plant. As a general rule, in cooler grow rooms, the plant requires higher nutrients. With warmer rooms, the plant requires lower levels of nutrients.

Vegetable Crops

L = Low   M = Medium   H = High

Product

pH

Category

cF

ppm

Artichoke

6.5 – 7.5

L

8 – 18

560 – 1260

Asparagus

6.0 – 6.8

L

14 – 18

980 – 1260

Bean (Common)

6.0

H

20 – 40

1400 – 2800

Beetroot

6.0 – 6.5

H

18 – 50

1260 – 3500

Broad Bean

6.0 – 6.5

M

18 – 22

1260 – 1540

Broccoli

6.0 – 6.8

H

28 – 35

1960 – 2450

Brussels Sprout

6.5

H

25 – 30

1750 – 2100

Cabbage

6.5 – 7.0

H

25 – 30

1750 – 2100

Capsicum

6.0 – 6.5

M

18 – 22

1260 – 1540

Carrot

6.3

M

16 – 20

1120 – 1400

Cauliflower

6.5 – 7.0

M

15 – 20

1050 – 1400

Celery

6.5

M

18 – 24

1260 – 1680

Cucumber

5.5

M

17 – 25

1190 – 1750

Eggplant

6.0

H

25 – 35

1750 – 2450

Endive

5.5

M

20 – 24

1400 – 1680

Fodder

6.0

M

18 – 20

1260 – 1400

Garlic

6.0

L

14 – 18

980 – 1260

Leek

6.5 – 7.0

L

14 – 18

980 – 1260

Lettuce

6.0 – 7.0

L

8 – 12

560 – 840

Marrow

6.0

M

18 – 24

1260 – 1680

Okra

6.5

H

20 – 24

1400 – 1680

Onion

6.0 – 6.7

L

14 – 18

980 – 1260

Pak – choi

7.0

M

15 – 20

1050 – 1400

Parsnip

6.0

L

14 – 18

980 – 1260

Pea

6.0 – 7.0

L

8 – 18

980 – 1260

Pepino

6.0 – 6.5

H

20 – 50

1400 – 3500

Potato

5.0 – 6.0

H

20 – 25

1400 – 1750

Pumpkin

5.5 – 7.5

M

18 – 24

1260 – 1680

Radish

6.0 – 7.0

M

16 – 22

840 – 1540

Spinach

6.0 – 7.0

M

18 – 23

1260 – 1610

Silverbeet

6.0 – 7.0

M

18 – 23

1260 – 1610

Sweet Corn

6.0

M

16 – 24

840 – 1680

Sweet Potato

5.5 – 6.0

H

20 – 25

1400 – 1750

Taro

5.0 – 5.5

H

25 – 30

1750 – 2100

Tomato

6.0 – 6.5

H

20 – 50

1400 – 3500

Turnip

6.0 – 6.5

M

18 – 24

1260 – 1680

Zucchini

6.0

M

18 – 24

1260 – 1680

Herbs

Product

pH

Category

cF

ppm

Basil

5.5 – 6.5

L

10 – 16

700 – 1120

Chicory

5.5 – 6.0

H

20 – 24

1400 – 1680

Chives

6.0 – 6.5

M

18 – 22

1260 – 1540

Fennel

6.4 – 6.8

L

10 – 14

700 – 980

Lavender

6.4 – 6.8

L

10 – 14

700 – 980

Lemon Balm

5.5 – 6.5

L

10 – 16

700 – 1120

Marjoram

6.0

M

16 – 20

1120 – 1400

Mint

5.5 – 6.0

H

20 – 24

1400 – 1680

Mustard Cress

6.0 – 6.5

M

12 – 24

840 – 1680

Parsley

5.5 – 6.0

L

8 – 18

560 – 1260

Rosemary

5.5 – 6.0

L

10 – 16

700 – 1120

Sage

5.5 – 6.5

L

10 – 16

700 – 1120

Thyme

5.5 – 7.0

L

8 – 16

560 – 1120

Watercress

6.5 – 6.8

L

4 – 18

280 – 1260

Flower Crops

Product

pH

Category

cF

ppm

African Violet

6.0 – 7.0

L

12 – 15

840 – 1050

Anthurium

5.0 – 6.0

M

16 – 20

1120 – 1400

Antirrhinim

6.5

M

16 – 20

1120 – 1400

Aphelandra

5.0 – 6.0

M

18 – 24

1260 – 1680

Aster

6.0 – 6.5

M

18 – 24

1260 -1680

Begonia

6.5

L

14 – 18

980 – 1260

Bromeliad

5.0 – 7.5

L

8 – 12

560 – 840

Caladium

6.0 – 7.5

M

16 – 20

1120 – 1400

Canna

6.0

M

18 – 24

1260 – 1680

Carnation

6.0

H

20 – 35

1260 – 2450

Chrysanthemum

6.0 – 6.2

H

18 – 25

1400 – 1750

Cymbidium

5.5

L

6 – 10

420 – 560

Dahlia

6.0 – 7.0

M

15 – 20

1050 – 1400

Dieffenbachia

5.0 – 6.0

H

18 – 24

1400 – 1680

Dracaena

5.0 – 6.0

H

18 – 24

1400 – 1680

Fern

6.0

M

16 – 20

1120 – 1400

Ficus

5.5 – 6.0

M

16 – 24

1120 – 1680

Freesia

6.5

M

10 – 20

700 – 1400

Impatien

5.5 – 6.5

M

18 – 20

1260 – 1400

Gerbera

5.0 – 6.5

H

20 – 25

1400 – 1750

Gladiolus

5.5 – 6.5

H

20 – 24

1400 – 1680

Monstera

5.0 – 6.0

H

18 – 24

1400 – 1680

Palm

6.0 – 7.5

M

16 – 20

1120 – 1400

Rose

5.5 – 6.0

M

15 – 25

1050 – 1750

Stock

6.0 – 7.0

M

16 – 20

1120 – 1400

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