Understanding EC.

Liz Filmer
10 Sep 2021

EC stands for electrical conductivity. Electrical conductivity is the ability of an object or, in this case, a solution to conduct an electrical current. Water that has had nothing added to it will have pretty much no conductivity at all. It is when you start adding other things to it that it gets interesting. 

In hydroponic growing, your nutrients are made up of mineral salts that are dissolved in water. The more salts in the water (nutrients added), the higher EC will be because the salts act as a conductor for electricity. You can therefore check if your nutrient contents correct by reviewing the EC of your feed solution. 

Like pH, you must understand EC and control it to manage your nutrient and water application correctly. Different plants need different levels of nutrients to grow to their optimum potential. By knowing the EC strength of your feed solution, you can provide your plant's with the perfect root zone conditions, which means that the plant is taking up the right amount of nutrients at the correct times. 

How do you do this? You use an EC reader. An EC reader features two electrodes distanced 1cm apart. You place the stick in the solution, and a current passes from one electrode to another. The reader will then tell you how much electrical current flows between these electrodes, giving you the result as a number. 

The higher the number, the higher the solution's conductivity (EC). The higher the conductivity, the higher the level of nutrients in the feed solution is. Once you have the result, you can then manipulate your nutrient feed to get it to/keep it at the desired EC level. 

EC correction is pretty uncomplicated. Start with a flush of pure water as most of the time, the cause of a too high EC is excessive nutrient doses. Following this, adjust your feed levels and be sure to monitor the EC. A light feed with added supplements like enzymes and carbs is the best way to get everything back where it should be.

EC value varies slightly depending on the strain. Generally, you will find that heavy-feeding Indicas like higher EC values of 2.5+. In contrast, you will find that some light-feeding Sativas prefer a low EC of 1.0; otherwise, they are at risk of over-fertilisation. As a general rule, the following is where your EC should roughly be for each stage of development. 0.8-1.3 for seedlings; 0.5-1.3 for clones; 1.3-1.7 for vegetative phase; 1.2-2 for flowering. However, you should. always check your specific strain for any differences.

You should monitor nutrient doses and evaluate pH and EC at every feed for accuracy, and fluctuations should be avoided wherever possible. EC should be gradually increased as your plant's behaviour dictates. You should also test runoff water weekly to prevent any salt build-ups, which is very important for hydro growers.


Liz Filmer