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Old 05-15-2015, 06:08 AM
jon1978 jon1978 is offline
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Join Date: Mar 2015
Posts: 10

Originally Posted by GpsFrontier View Post
On smaller scale recirculating systems, they simply change the nutrient solution regularly to ensure a balanced nutrient solution. On large scale recirculating and water culture systems where it's not reasonable to change out large volumes of water regularly. Either the water or the plant's foliage is lab tested (regularly) to determine if the nutrient solution is balanced. If not, then only the depleted mineral salts are added back. Through regular testing it's fairly easy to see a pattern in order to add specific mineral salts at specific times to maintain a balanced nutrient solution for a specific crop.
But if I use a circulating system it won't be a uniform dose because the first plants will have more nutrition than the ones on the last end. If I use a circulating system I will ensure a uniform dose, all plants will recieve the same. If I flush the reservoir each night the problem you describe does not really seem to apply.

Typically with computer controlled systems that use a reservoir the EC and pH is monitored and/or adjusted in the reservoir. Not in feed lines to plants unless the system/computer is capable of determining and adjusting the injection ratio variables on a continues basis. But plants don't use nutrients evenly, they take what they need and leave the rest. That means even if your EC readings are at the same level when your nutrients were fresh, over time the balance of those nutrients will change. Eventually you will have deficiencies of some, and others will be at toxic levels, even though the EC reading is exactly the same. That's why injectors aren't typically used in recirculating systems except to adjust pH, or add specific mineral salts at specific times that are known to be depleted quicker through lab testing. Each different mineral salt and pH adjustor (up/down) will need it's own injector and feed lines.
So how do you automate a recirculating system if not by dosers?

Are you planing to change the nutrient solution in the reservoir each day? Or is this a non-recurlating system. Where does the water go once it reaches the end of the NFT gullies/tubes?
I don't plan to change the nutriton solution every day but I want to be able to do it if I want to. The water is supposed to go back to the reservoir but I simply add a flush valve to a solenoid so every night at 3 AM the reservoir empties out and I start adding new water for the morning. If I dimension the reservoir to the size of the line properly it will not be much water that empties out and in a large system I can reclaim it if necessary through photoalgaeic treatment.
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