The EC meter measures the amount of water soluble (mainly fertilizers). The higher the concentration of fertilizers in the irrigation solution, the higher the EC value. An EC meter measures the potential for an electrical current to be transported through water. When we add nutrients (salts) to water, we increase the conductive potential for current through water, and thus increase the EC value. The EC is affected by temperture also. Pure water is a poor conductor of electricity, which is why an EC meter will read 0.0 in rainwater, reverse osmosis water or de-mineralized water. Salty seawater, on the other hand, is a much better conductor.
Fertiliser is made up of nutritional salts.
The plants use the water of the irrigation and also the nutrients/salts/fertilizers that we supply them. So actually they take salts out of the irrigation solution and lowering the EC. If we supply the plants too much salts than they can handle, in each irrigation, we gradually salting the roots enviroment, which will end in a suffocation of the plants, and slowing down their growth rate, and even damaging it, because as the solution becomes saltier the plants have more and more difficulty consuming the water. If the EC becomes too high, especially in hot climate conditions, the plants may not be able to consume enough water Even for their basic needs. The leaves will begin to wither, their tips will turn brown, and at this point, if the problem is not resolved immediately, the salt will begin to ‘pump’ the water from the plant roots which will cause the plant to wither.
One of the most common mistakes that beginner growers make is over-fertilization. Different plants prefer different levels of fertilizer and all plants prefer different levels as they progress in their growth stages. For example, plants in the vegetative stage (growth stage) will prefer lower fertilizer levels, which means that our solution will be more diluted with water. Low-medium EC levels, promotes vegetative growth and facilitates the young plants in the process of water absorption and nutrients. In the vegetative growth phase it is recommended to maintain an EC value in the range of 1.2-1.6. Mature plants, can deal with EC at full power as they enter the flowering and embalming phase of the fruit. The EC value of a full-strength fertilizer solution intended for the flowering and fruiting stages will be about 1.8 – 2.2.
If you reach an EC value of 3.0 and above, its too high, you will need, for one time, to double the irrigation dose with only water and wash the soil, and you will need to lower the EC level, if by raising the water dose at each irrigation or by adding less fertilizers. It is advisable to check the EC, on daily basis.
The presence of EC alone does not necessarily indicate that the water contains nutritional salts, that will help plants. Tap water can contain sodium and chloride, for example, which have an EC value but no nutritional value for plants. There are places that the tap water themselves, already have a high EC of 1.5 or more, usually water that are sucked up from wells.
The solution, that we use to measure the EC, is extracted from the near enviroment of the plant’s roots in the soil, using the soil water sampler, or in hydroponics from the runoff water that is coming out of the pot.
Sodium (Na) and chloride (Cl-) are harmful components that are dissolved in the roots and come, in most cases, from irrigation water. Care must be taken with the irrigation interface, that will prevent the increase in their concentration.
Excess chlorine creates stress conditions for the plant.
At values above 300ppm of chloride, rinsing is recommended – a double dose of water, than the regular dose of irrigation.