USDA/ARS Hydroponics/Aquaculture Effluents Project (fwd)

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From: "Gary L. Jensen" gjensen@morrill.esusda.gov

The following is a summmary of research into uses of rainbow trout effluent and manure for plant production and water treatment provided by the research staff at the USDA-ARS Appalchian Fruit Research Station in Kearneysville, WV. I encourage you to contact the persons listed for more details about this work if interested.

Gary Jensen

We have developed plant production systems that are highly productive and effectively remove polluting nutrients from aquaculture waste water. Because greenhouse space is expensive, productivity is critical for a profitable operation. We term our production system the "conveyor production system". In the conveyor system, young plants are positioned near the solution inlet of a hydroponic trough and are moved progressively towards the outlet as they grow. In this thin-film technology, phosphorus is removed to levels less than 10 ppb by lettuce and basil without a reduction in yield or quality. In the conveyor system, luxury consumption of P by young plants early in their development sustains them at later stages of growth as the phosphorus concentration decreases in the effluent. In a sense, the plant has a nutrient savings account with early deposits and withdrawls delayed until nutrient levels in the effluent are insufficient to meet daily needs. We developed a mechanistic approach because it provides a framework to direct research and identify the data that needs to be collected so experiments based on different effluent sources can have more general application.

We have expanded this concept to hydroponic production of strawberries using vertically-stacked pots. In this system, containers of vermiculite media are stacked to a six foot height (24 plants/stack). The effluent is delivered to the top container using a pulse irrigation system (Intertec, Lynchburg, VA) and drips through the lower containers, supplying water and nutrients. Plug plants of 'Chandler' yielded over 600 g/plant from January to March while reducing effluent P from 700ppm to less than 100 ppm. Neither the conveyor or vertical pot system recycle the effluent, the effluent passes through the plant system only once.

The aquaculture solids (manure and feed) were composted and the compost used as planting media for lettuce production. We found that compost fish waste was as good or better than sponge or rock wool due to the nutrients it contained and it provided disease suppression of water-borne pathogens (Pythium species), a trait not found in inert media. Composting the fish waste eliminated a disposal problem and further recycled the by-products of aquaculture into money making uses.

For further information contact:

Paul Adler-Horticulturist ext 352 ftakeda@asrr.arsusda.gov

Michael Glenn-Soil Scientist ext 321 dglenn@asrr.arsusda.gov

 USDA-ARS Appalachian Fruit Research Station
 45 Wiltshire Road
 Kearneysville, WV 25430
 304-725-3451

  GARY L. JENSEN
  USDA/CSREES/PAPPP
  Ag Box 2204
  Suite 302-C, Aerospace Center
  Washington, DC 20250-2204
  tel: 202/401-6802
  fax: 202/401-1602
  internet: gjensen@reeusda.gov
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