Hanna Instruments HI 993310 User Manual

Page 5

NUTRITIVE SOLUTIONS
The nutritive solutions constitute one of the most important factors in
determining the plant’s growth and yield. Hence, putting the right
solution at the plant’s disposal is indispensable to get the best result.
Conductivity (EC) of nutritive solutions must be checked regularly to ensure
that it agrees with plant’s requirements. The plants also have seasonal
preferences, typically requiring lower concentrations in the summer.

Melon
Potato
Pepper
Pea

1.50-2.50 mS/cm
2.00-3.00 mS/cm
2.00-3.00 mS/cm
1.00-1.50 mS/cm

Tomato
Celery
Marrow

2.50-5.00 mS/cm
2.00-2.50 mS/cm
2.00-2.50 mS/cm

Asparagus

Watermelon

Carrot

Cabbage
Cucumber
Chrysanthemum

1.50-2.00 mS/cm
1.50-2.50 mS/cm
1.50-2.00 mS/cm

2.00-3.00 mS/cm
2.00-3.00 mS/cm

1.50-2.50 mS/cm

PLANT

PREFERRED EC VALUES

Onion
Bean

Strawberry

2.00-2.50 mS/cm

Lettuce

Egg plant

1.00-1.50 mS/cm

2.50-3.00 mS/cm

1.50-2.00 mS/cm

Class I: This type of water can be used without any quantity limitation.
Class II: Only a limited quantity should be used depending on the

irrigation techniques and the crop.

Class III: May be used occasionally, but only for tolerant plants and/or

well-drained soils.

Class IV: To be used only if there is no other alternative and as little as

possible.

IRRIGATION WATER
The irrigation water must be checked regularly, especially in the hydro-
ponics industry. Conductivity is the most important parameter to check
since plants can be seriously damaged by too high EC value.
Water used for irrigation has been classified in four classes, depending on
its conductivity:

Class I
Class II
Class III
Class IV

EC < 0.75 mS/cm

EC = 0.75 to 2.50 mS/cm
EC = 2.50 to 4.00 mS/cm

EC > 4.00 mS/cm

WATER CONDUCTIVITY

SATURATED SOIL-PASTE CONDUCTIVITY
The conductivity value of the saturated soil-paste can be used for
classifying the salinity level of the soil and also provides indications
about the soil productivity, depending on plants (see also the table
on next page for reference).

Response of cultivations depends also from different saturated soil-
paste conductivity values.
Find below a schematic classification made by the

U.S. Salinity Lab.

Riverside - CA.
• EC = 0 mS/cm : the salinity effect is negligible.
• EC = 2 mS/cm : the crop of the more sensible cultivations can be

reduced.

• EC = 4 mS/cm : the crop of many cultivations is reduced.
• EC = 8 mS/cm : only tolerant plants produce a satisfactory crop.
• EC = 16 mS/cm : only a few very tolerant plants produce a

satisfactory crop.