Red:Blue ratios differently change yield, nutritional quality and water use efficiency of twelve microgreen crops

Abstract Microgreens are young seedlings harvested at the first true leaf stage and are valued for their concentrated flavour and phytonutrients. Their short growth cycle and high planting density make them well-suited for Totally Controlled Environment Agriculture (TCEA), which shields crop performance from external weather and water scarcity. However, species-specific water footprints for these juvenile crops remain limited, which inhibits accurate sustainability claims. This study evaluated twelve culinary microgreen species representing Amaryllidaceae, Asteraceae, Brassicaceae, Cucurbitaceae, Fabaceae and Lamiaceae , cultivated in a micro-TCEA unit under two LED spectra with contrasting Red:Blue ratios (5.08 vs 2.33; 255 µmol m −2 s −1 ; 14 h photoperiod). Ranking species by days to harvest and cumulative water use produced a multidimensional efficiency matrix linking physiology to resource demands. The analysis revealed clear interspecific differences in growth duration and water consumption, which directly affected water-use efficiency (ranging from 73 to 154 g biomass L −1 ). Spectral treatment did not alter biomass, water use efficiency, nitrate, or phenolic content, confirming nutritional parity across light regimes. The observed variability among species in crop length and water budget highlights that early-stage demand is primarily driven by intrinsic physiological traits. Adopting species-specific irrigation set points offers a high-leverage route to maximise yield while minimising water withdrawal, providing a practical framework for cultivar choice, scheduling, and climate-adaptive strategies in precise horticulture.