Bulk Electrical Conductivity and Water Use as Indicators of Root-Zone Nutrient Balance

This poster was presented at CANVAS 2026 in Portland, Oregon, November 1–4, 2026. It reports ground tests of bulk electrical conductivity (EC) and water use as indicators of root-zone nutrient status during two successive leafy-green crop cycles in the zero-discharge Utah Reusable Root Module (URRM) simulator. Bulk EC and water use were evaluated alongside root-zone solution EC, nitrate-N concentrations, and nutrient removal in harvested biomass. During the final two weeks of the second crop cycle, root-zone solution nitrate-N fell below the analytical detection limit of 0.5 mg N L⁻¹ across all leafy-green crops. Bulk EC was more closely related to solution EC than to nitrate-N concentration, highlighting the limits of bulk EC for detecting nitrate depletion. These findings inform nutrient monitoring for repeated vegetable production in reusable root modules designed for the International Space Station.