Target EC, ppm (500 & 700 scale) and pH by growth stage. Every row traces to published university controlled-environment research.
| Crop & stage | EC (mS/cm) | ppm (500) | ppm (700) | pH | Source |
|---|---|---|---|---|---|
| Leafy greens & herbs | |||||
| Lettuce — seedling | 0.8–1.2 | 400–600 | 560–840 | 5.6–6.0 | Cornell CEA |
| Lettuce — mature head | 1.4–1.8 | 700–900 | 980–1260 | 5.6–6.0 | Cornell CEA |
| Leafy greens — kale, chard, spinach, arugula | 1.2–1.8 | 600–900 | 840–1260 | 5.8–6.2 | Penn State |
| Basil | 1.4–1.8 | 700–900 | 980–1260 | 5.5–6.0 | Penn State |
| Leafy herbs — cilantro, parsley, mint, chives | 1.4–1.8 | 700–900 | 980–1260 | 5.5–6.0 | Penn State |
| Microgreens — all cultivars | 1.0–1.8 | 500–900 | 700–1260 | 5.8–6.2 | Produce Grower |
| Fruiting crops | |||||
| Strawberry | 1.2–1.8 | 600–900 | 840–1260 | 5.8–6.2 | UF/IFAS |
| Pepper — bell & chili | 1.8–2.4 | 900–1200 | 1260–1680 | 5.8–6.2 | Cornell CEA |
| Cucumber | 1.8–2.4 | 900–1200 | 1260–1680 | 5.8–6.2 | UF/IFAS |
| Tomato — seedling | 1.2–1.6 | 600–800 | 840–1120 | 5.8–6.2 | Penn State |
| Tomato — vegetative | 1.8–2.2 | 900–1100 | 1260–1540 | 5.8–6.2 | UF/IFAS |
| Tomato — fruit set | 2.2–2.8 | 1100–1400 | 1540–1960 | 5.8–6.2 | UF/IFAS |
EC is the source value — the two ppm columns are just conversions: 500 scale = EC × 500 (Hanna, Bluelab); 700 scale = EC × 700 (Truncheon, HM Digital). The same solution reads a bigger number on the 700 scale, so match the column to your meter. Run the low end early (young roots are salt-sensitive), raise EC through vegetative growth, and shift fruiting crops toward more potassium at fruit set. Subtract your source-water ppm before dosing. Most hydroponic vegetables and herbs feed best at pH 5.5–6.5.