PURPOSE: To provide a fertilizing system for hydroponics excellent in plant growing effect through securing oxygen feed from plant roots without unnecessary loss, by evaporation, of a nutrient-contg. liquid fertilizer.

CONSTITUTION: The system is made up of (A) a reservoir 1 for a liquid fertilizer prepared by dissolving nutrients required for plant growth and (B) a porous ceramic vessel 10 communicating, via a pipe 6, with the reservoir 1, located below the reservoir, and capable of suction of a liquid fertilizer externally through the attractive force of plant roots. Thereby, plant roots are spread around the ceramic vessel 10 filled with a liquid fertilizer and the fertilizer is brought to suction by the attractive force of these roots; therefore, the liquid fertilizer itself does not come to direct contact with the air and oxygen becomes suppliable from part of the plant roots at all times.