Electrical Conductivity: How it Works?

Stephen Andrews
04 Feb 2022

Electrical conductivity or EC is the ability of an object or, in this case, a solution to conduct an electrical current. Water without any additives in it has no conductivity, but when you pour in stuff like nutrients, such as with other properties, EC changes, too.

When growing in a hydroponic setting, your nutrients consist of mineral salts dissolved in water. The more salts/nutrients added to the water, the higher the EC, and for a simple reason: salts act as a conductor for electricity. Checking the nutrient contents can help determine if EC is stable or whether you need to make corrections. 

As with pH, growers must know EC and control it in order to manage a balanced nutrient and water uptake in cannabis plants. With an optimal EC strength of your feed solution, growers can provide crops with the perfect root zone conditions, which helps the plant take up the correct amount of nutrients at preferred time intervals. 

The tool you need here? An EC reader or EC meter. It's a simple stick that uses two electrodes to measure the current in the solution. The reader will then tell you how much electrical current flows between these electrodes, giving you the result as a number. 

A higher number means a higher conductivity (EC) in the solution. Or, in other words, there's a higher level of nutrients in the feed solution. When you know the result, you can take steps to correct the nutrient feed and establish a more appropriate EC level. 

EC correction is simple. The most common reason for disbalance is excess nutrient doses. That is why you need to start with a flush of pure water to eliminate the excess. After you flush, readjust the feed levels and continue monitoring the EC numbers. Use a light feed with added supplements such as enzymes and carbs to balance things out. 

EC values are slightly different for specific strains. However, while you should always consider what strain you are growing, there are some general rules to follow where the EC number roughly should be. For example:

  • Heavy-feeding Indicas appreciate higher EC values of 2.5+.
  • Light-feeding Sativas do well with a low EC of 1.0.

As per stage of growth, the following values are applicable:

  • For seedlings: 0.8-1.3
  • For clones: 0.5-1.3
  • During vegetative phase: 1.3-1.7
  • During flowering: 1.2-2

It's recommended that you monitor nutrient doses and assess pH and EC values at every feed for accuracy, and avoid fluctuations where possible. Electrical conductivity should be gradually increased as your plant's behavior dictates. It's also recommended that you test runoff water to prevent salt build-ups, essential when growing in hydroponics. 

Stephen Andrews