EC, also displayed as mS/cm, refers to the electrical conductivity of a nutrient solution. It is directly proportional to the amount of ions dissolved in water. For the sake of simplicity, the higher the EC, the stronger the nutrient solution is.
The EC of a nutrient solution is derived from two main things, mineral ions and organic ions. Mineral ions are the core of plant nutrition and are usually the biggest contributing factor to the overall EC of a nutrient solution. The major mineral ions are Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulfur and Iron. Each of these minerals has a specific electrical charge and some of them are stronger than others. Increasing or decreasing any of these elements will change the overall EC of the nutrient solution.
EC is also derived from organic ions like humic/fulvic acids, amino acids and kelps. These organic ingredients will increase the EC of your nutrient solution without necessarily adding additional mineral nutrients (or food). The higher the EC is, the harder it is for a plant to absorb the water it needs from the nutrient solution.
If you already use EC or mS/cm, perfect! If you aren’t, you really should start. EC is both simple to use and universal. 1.5 EC will always be 1.5 EC – in every country, in every situation and with every meter. There really isn’t any better measurement!