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Nutrient depletion and replenishment

Posted by chuck Z10,SW FL ( on
Thu, Oct 18, 12 at 4:25

I had thought that I might be able to replenish the nutrients as they are used by the plants, but I suspect the ratios of the various components are constantly changing. So, to restore the nutrient mix to its original levels, a chemical analysis would be required. Perhaps in a large operation, replenishing the nutrient solution may be cost effective. My system has around 100 gallons nutrient mix that circulates through it. I use the special hydroponic mix sold by Southern Agriculture. It comes in 25 pound bags and runs under $30 dollars. For mixing up 50 gallons of mutrients, I use 1 cup of this product along with 1/4 cup of epsom salt, and 1/2 cup of calcium nitrate. I get a TDS reading of around 800, up from a reading of 130 for city tap water. I haven't figured out the exact cost per gallon, but I think it comes out to be less than 5 cents a gallon.

The cost is low enough that I think the best procedure will be to dump the entire mix once a week and mix up a new batch. I found small bags (4 pounds) of calcium nitrate on ebay, and epsom salts can be found in any big store.

Follow-Up Postings:

RE: Nutrient depletion and replenishment

buy calcium nitrate from the same people you get the soluble hydro from or from a landscape supply company. I think it runs about $50 for a 50lb bag. your TDS sounds about right with what I typically run.(620ppm) you don't need to change it weekly. you're dumping to much fertilizer into to ground that way. When the water runs low, check the EC and add water or concentrated solution to bring it back to normal or a balanced solution if it is normal. only change it every two weeks to one month. You can actually run it that way longer if you wish, but then you may start to see more effects from an imbalanced nutrient solution. (I've run them 2+ months that way)
To be truly environmentally friendly you collect your "leftover"'s after each change out in a larger container. After you've accumulated enough (say 10 changes) you have that bulk mixture tested and balance it back to what you need. But for a home grower that is probably a bit much.

RE: Nutrient depletion and replenishment

It would be a lot easier if your nutrient solution was not exposed to light and air. You don't really know what your plants are using, versus what water you are losing to evaporation and what nutrients you are feeding to algae.

RE: Nutrient depletion and replenishment

I use Maxibloom from General Hydroponics which comes out to 8 cents a gal when mixed 1 tsp per gal of water.

RE: Nutrient depletion and replenishment

^^ I have also used the Maxiseries dry nutrients by General Hydroponics. Here is a cucumber grow in a DWC with the Maxi
nutrients ONLY:


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