Completely Passive, Non-Recirculating Hydroponic Systems : Some Tips for Large Plants

On yesterday's post I talked about the existence of completely passive, non-recirculating hydroponic systems and how they can be successfully used for the growth of almost any hydroponic crop you can imagine. Following on this post's idea today I want to share with you some tips to use this type of system with larger plants so that you can effectively setup your own hydroponic passive farm with the least amount of effort and chance of failure. On today's post I will talk about the media and system characteristics for the raising of large plants, particularly plants like tomatoes, cucumbers and bell peppers which require large amounts of oxygen, nutrients and solid media support.

If you read the previous post you might remember that when using large plants -like the ones mentioned above - the best thing is to use a media filled container in which the nutrient solution is first close to the surface and then slowly gets used and evaporates from the nutrient solution. However it is also important here to say that there are some specific requirements for the media and some important changes that can be made to guarantee that success will be much more likely to happen.

The solid media used is better divided in two, the first media is a highly absorbent, capillary efficient media (like rice husk combined with sand 1:1) which is put in a small cup or container while the second media is a non-absorbent very capillary deficient media like gravel which is used to occupy the rest of the available space. Other coarse media can also be used to fill the rest of the container like vermiculite or other types of rocks. The important thing here is that the whole media must NOT be efficient at capillary absorption because this will make the whole media wet all the time and it will drown the roots since the "air space" will be non-existent.
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You can follow the diagram above to build a system for a large plant. Note that the container for a large cucumber or tomato plant must be at least 5 gallons and solution needs to be added at a rate of about 1 gallon a month through the crops full life. Note that inserting a small PVC pipe to control volume within the container is always a good idea since you don't want to put so much solution to drown the roots and make the plant die. Mature tomato plants require a space of at least 50cm of air roots when they are older for their proper development so make sure the container you use is about 70-100 cm tall when you build your system.

Hopefully with this advice you will be able to start your first passive large-plant hydroponic garden without using any electricity. Also remember that this setup requires absolutely no EC or pH adjustments since once added the solution won't be able to be modified. This however does not cause any problems since the plants adapt to the solution and pH levels acquired. You can also increase the EC or change the nutrient ratios depending on the plant's stage when you perform the monthly nutrient solution additions to your plant's personal reservoir. Please feel free to leave any comments with your experiences with this technique !

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10 Responses

  1. Adley
    Hi! Im interesting on this idea, but i have a question that could not use any substrate to achieve this?
  2. Daniel
    Hello Adley,<br /><br />Thank you for your comment, however I do not understand your question very well. The system can be used without substrate (only the capillary substrate within the cup where the plant is placed) if there is enough structural support to hold the plant. However if the plant is very big the whole system should contain substrate as it is shown above. I hope this answers your inquiry,<br /><br />Best Regards,<br /><br />Daniel
  3. Adley
    Hello Daniel, <br /><br />Thank you for your reply. My whole idea is that I want to use a water bottle as container which filled with water. And put the plant to touch the water. I am not really sure that will be ok? <br /><br />Thank you.
  4. Daniel
    Hello Adley,<br /><br />No, that won't work. You need a top capillary media in the beginning so that plants can have an initial "wet space" that also contains oxygen, then as they grow into the solution and take water the evaporation causes the creation of an air-buffer zone where the roots can take in oxygen. In a water bottle with the roots initially within the solution and no initial capillary media the roots would simply die because of lack of oxygen. Also the very limited volume of a bottle means you would only be able to grow very small plants, plants like lettuce at most. I hope this helps,<br /><br />Best Regards,<br /><br />Daniel
  5. Adley
    Hi Daniel,<br /><br />Thank you very much! If I use the bubble generators, would solve the oxygen-lack problem? <br /><br />Adley
  6. Daniel
    Hello Adley,<br /><br />Sure, that would solve the problem but then the system would need electricity and it would not be totally passive. However if your objective is to grow a plant in a bottle that might work. However you will still be restricted to small plants because of the volume,<br /><br />Best Regards,<br /><br />Daniel
  7. Mike Smith
    Daniel, I realize that for this to work some portion of the roots must be "air roots". I am confused how you are maintaining enough roots in the air. It seems like the mass of the root ball will be on the bottom of the reservoir. What method are you using to maintain the "air roots" if I can trouble you to ask. Thanks in advance, Mike
  8. kaveh
    hi, please let me know which kind of filtration needs for water recycle treatment in closed hydroponic system? if possible send me a hydroponic commercial greenhouse design for recycling water system.thanks
  9. Cyprian
    It is interesting to learn that one can grow tomatoes through hydroponic without electricity. Please can I have more information on options of run a hydroponic without electricity as it will be greatly suitable for my environment in Africa where there is no regular electric power supply
    • GROWA
      Hi Cyprian, You can easily grow hydroponics outdoors. The cheapest system is using a kids pool as a reservoir or an open top tank, shade cloth over top, then using a ball valve garden timer to feed through a 120 micron disc filter, then through pressure compensating drippers, (TORO 2LP/HR is the best) Just us low dense poly and 4mm spaghetti to connect. You can drip feed a few times a day into just straight coco peat or soil and perlite or sand or just dirt and mulch mixed anything the will give some airation and drainage so that not too much water is hanging around the roots for too long. Though spraying phosponic acid every 2 weeks will prevent any of that. Design you nutrient solution as direct addition keeping it in powder form as a + b. drop a into a 70L garbage bin full of water and stir with a short paddle for about 30 seconds, once diluted then bucket it into the reservoir and mix it about a half wirlpool rotation, repeat with part b, ph adjustment and a couple of full rotations from both ends stirring, check EC at both ends to ensure even mix and its done.

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