A measure of the concentration of dissolved nutrients in a feed solution. Higher EC indicates a stronger nutrient solution; too low an EC can lead to nutrient deficiency.
Mr. Q diagnosed the CO2 room clones as likely suffering from too-low EC in addition to overwatering, citing nitrogen-deficient and pale new growth as evidence. Dakota's solution was to step up the EC on the next feeding round. Later, Dakota confirmed he cranked up EC along with cal-mag when the plants recovered.