The most recent publicly made statement from the National Organic Program (NOP) is that hydroponics may be certified because the NOP regulations do not prohibit hydroponics. There are several certified organic hydroponic operations in the United States that are certified by USDA accredited certifying agents.
The National Organic Standards Board (NOSB) came out with a recommendation in April of 2010 recommending rulemaking for production standards for terrestrial plants in containers and enclosures. Final NOSB Recommendation on Terrestrial Plants. The NOP responded to the NOSB recommendation by saying they would develop a proposed rule on greenhouse standards (including hydroponics) based on the NOSB final recommendation.
NOP is considering specific standards for organic hydroponic operations, but we have not seen a proposed rule to date. In the meantime, hydroponic operations certified under the NOP must comply with the organic crop regulations as they are written. OTA will continue to monitor the process and engage members in the comment process as soon as the proposed rule is released.