Gravimetric methods, measuring differences in pot mass to determine plant water use and irrigation amount, are used to study water stress physiology and associated yield reductions in crop species. These methods however cause undesirable assumptions, and are expensive and labourious. To avoid these disadvantages a novel bottom-watering culture system was developed. It was constructed of plastic pipes and utilises passive flow to maintain specific volumetric soil water content (VSWC) while tracking plant water use. VSWC in the rooting zone is controlled by altering the height of the water table in the bottom 50-cm portion, as controlled by an external float valve. Water stress induced in this manner reduced VSWC by 50% and soybean biomass accumulation by 53%.