Biological buffering maintains stable pH from acidic to alkaline conditions in single nutrient source hydroponics

A newly designed single-nutrient source hydroponic solution allows precise nutrient manipulation but presents challenges in maintaining stable pH, a key factor in controlled plant nutrition studies and commercial hydroponic systems. The objectives of this study were to evaluate soybean (Glycine max (L.) Merr.) grown with 2-(N-morpholino)ethanesulfonic acid (MES) as a biological buffer to manage pH in the new system. Plants were grown in a single-nutrient source hydroponic solution amended with MES at concentrations of 0, 6, 8, 12, 60, and 80 mM. Increasing MES concentrations lowered and stabilized solution pH, with average values of 8.0, 7.5, 6.5, 5.8, 5.0, and 4.8, respectively. The pH stability was increased with increasing MES concentrations, with reasonable to excellent buffering ≥ 8 mM MES. The highest two MES concentrations resulted in phytotoxicity. The use of MES effectively stabilizes pH in the single-source hydroponic system, supporting healthy soybean growth across a range of acidic to alkaline conditions. Concentrations between 6 and 12 mM are recommended for soybean to improve system utility and enable controlled nutrient deficiency studies.