Electrical Conductivity (EC)

EC is reported in three forms agronomists routinely encounter: ECiw (irrigation water EC, measured at the well or canal), ECe (electrical conductivity of saturated soil paste extract, the lab gold-standard), and EC1:5 (a quicker 1:5 soil-to-water suspension; multiply by ~2 to approximate ECe in coarse soils). All three correlate but are not interchangeable; published crop-tolerance tables (Ayers & Westcot 1985, FAO DP29 Table 1) use ECe.

Crop salt-tolerance is published as an ECe threshold + slope (% yield decline per dS/m above the threshold). Date palms tolerate ECe up to 8 dS/m before yield declines at 3.6%/dS/m; olives 4.0 with 9.5%/dS/m; wheat 6.0 with 7.1%/dS/m; lettuce just 1.3 with 13%/dS/m. Maas-Hoffman classifications group crops into sensitive (<1.5), moderate (1.5–4.0), tolerant (4.0–8.0), and halophyte (>8.0). On saline farms, choosing a salt-tolerant crop is more economically powerful than any amendment — barley over wheat, date palm over citrus, sugar beet over potato.

Management strategies in saline conditions: (1) calculate a leaching fraction so each irrigation cycle delivers extra water to flush salts below the root zone; (2) blend high-EC well water with rainwater or municipal supply to reduce ECiw at the emitter; (3) increase irrigation frequency under drip to keep soil EC near the wetting front low; (4) acid-flush drip lines monthly above EC 2.0 dS/m to prevent emitter clogging from carbonate precipitation. WiseYield's lab-analyses module captures EC at the well, soil, and leaf level and feeds the value into the irrigation advisor's leaching-fraction calc.