EC (Electrical Conductivity)

EC (electrical conductivity) is the standard global measurement for fertilizer concentration in liquid nutrient solutions, replacing the inferior PPM scale used in older American growing literature. EC measures how readily an electrical current passes through a solution — pure distilled water has near-zero conductivity, while heavily fertilized solutions conduct electricity efficiently because dissolved nutrient ions (N, P, K, Ca, Mg, micronutrients) carry electrical charge. Optimal EC for cannabis varies dramatically by lifecycle stage: Seedlings/clones (0.4-0.8 mS/cm) — minimal nutrients to avoid burning underdeveloped roots; Early veg (1.0-1.4 mS/cm) — moderate feed as root systems develop; Late veg (1.4-1.8 mS/cm) — full nitrogen feed for maximum vegetative growth; Stretch/transition (1.6-2.0 mS/cm) — gradual shift from veg formula to bloom formula; Mid flower (1.8-2.4 mS/cm) — peak nutrient demand during bud development; Late flower (1.6-2.0 mS/cm) — slight reduction as plants shift to ripening; Flush (0.0-0.4 mS/cm) — pure pH-balanced water in the final 7-14 days to clear stored nutrients. EC measurements are taken with a calibrated EC meter or combination pH/EC pen submerged in the nutrient solution. Successful growers track both feed-in EC (what you mix) and runoff EC (what drains from the pot) — runoff EC significantly higher than feed-in indicates nutrient buildup and pending lockout, while runoff EC lower than feed-in indicates rapid uptake and the need to feed more concentrated solution. EC is universal across all hydroponic, coco, and even soil-fertigation systems.