Different types of hydroponic systems run at slightly different maximum levels as the roots are fed in slightly different ways.

It is impossible to give specific figures as there are so many variations, but general guidelines are given below. If the specific figure for a plant cannot be found then you will have to work it out by trial and error, slowly increasing the conductivity level of the nutrient solution.

EBB AND FLOOD (OR FLOOD AND DRMN)

Although ebb and flood systems usually use a growing medium the roots are not always exposed to the nutrient solution, so the average figures should be used.

NUTRIENT FILM TECHNIOUE (N.F.T.)

As N.F.T. systems have no growing medium and the roots are exposed to the nutrient solution for most of the time a higher conductivity level can be maintained.

HYDRO-POTS ETC.

Growing mediums (such as expanded clay pebbles etc) are slightly alkaline and they can also ‘hold’ on to nutrients. In order to compensate for this, systems using such growing mediums should be run at slightly lower conductivity levels.

The table below shows the maximum conductivity levels for a plant with a range of C.F. 16 — 24, grown in the different types of hydroponic systems.