The electrical conductivity (EC) is a measure of potential transport of an electrical charge in water.
In gardening this measure is used to know the amount of nutrients in a fertilizer solution, although the fact that a solution having a certain EC level does not mean containing salts which have nutritional value for plants. For example, tap water can contain chlorides, which increase the EC level but do not provide nutrition to plants.
To maintain an optimal level of salt exchange between the medium and the plant must comply EC levels increasingly. The reason is that the salts attract water through a process called hydrolysis, so that, adding a nutrient solution to the plant salts it contains attract water from the substrate and hinder the root can absorb it, so when we talk about excess of fertilization it is in fact a difficulty for plants to hydrate.
Part of the nutrients absorbed by the plant will be transformed into amino acids, proteins, etc., but part of them will join the sap, increasing its internal EC. This increase in EC facilitates the absorption of water by the plant, enabling increased nutrient solution EC in each irrigation thus meeting the growing needs of this during its early stages.
Increase of EC must be controlled from the last third of plant life, since then it has absorbed a large amount of nutrients and there’s a risk of a dramatically increase of the substrate EC, so in the latter period fertilization of culture medium should be reduced, since if the substrate has not enough water could greatly increase salt concentration, preventing the hydration of the plant.