Hydroponics is an excellent technique for the cultivation of vegetable crops and other plants, but organic
fertilizers cannot be used in conventional hydroponic systems, which generally use only inorganic fertilizers,
because organic compounds in the hydroponic solutions generally have phytotoxic effects that lead to poor
plant growth. Few microorganisms are present in hydroponic solutions to mineralize the organic compounds
into inorganic nutrients. In this article a novel and practical hydroponic culture method that uses
microorganisms to degrade organic fertilizer in the hydroponic solution has been developed. Soil
microorganisms were cultured by regulating the amounts of organic fertilizer and inoculum, with moderate
aeration. The microorganisms mineralized organic nitrogen via ammonification and nitrification into nitrate
at an efficiency of 97.6%. The culture solution containing the microorganisms was usable as a hydroponic
solution, and organic fertilizer could be directly added to it during vegetable cultivation. Vegetables grew well
in the organic hydroponic system. Organic hydroponics based on this method is therefore a practical tool for
the utilization of organic sources of fertilizer.