EC/CF in a Nutrient Solution
The function of a nutrient solution is to supply the plant roots with water, dissolved oxygen and essential mineral elements in soluble form. The success of a hydroponic system depends heavily on the correct control of this nutrient solution in terms of strength.
Each plant has its preferred solution concentration to facilitate the absorption process to the roots. Choosing the correct strength at each growing phase of the plant will result in optimum growth. See Chart 2 optimum pH/EC levels (below).
We most commonly measure a nutrient's concentration by measuring in EC, CF and ppm (parts per million) values. Nutrient solutions must be monitored as frequently as possible. The warmer your growroom the more water the plant will use and transpire, thus increasing the nutrient strength. As water evaporates or is used by your plants transpiring, the salt level will increase meaning your EC/CF value will rise. High EC/CF values, mean a high nutrient concentration which if too high can be toxic to the root zone and will cause poor and stunted growth. At extreme levels, too high a level will cause actual death in the root zone. When planting out you start with a weak solution then increase nutrient EC/CF levels gradually over time rather than suddenly and all at once.
How to Measure EC/CF
EC/CF in a Rockwool Slab System
CF Standard (CF28)