Recirculating System Dosing Controllers
Recirculating Hydroponic systems are those which have a central mixing tank from which the crop is fed. The nutrient solution then returns to that tank via gravity or pump.
Examples of this include:
NFT Hydroponic Systems – A pump runs 24 hours a day, 7 days a week to draw nutrient solution from the central tank and pumps it out to above ground growing benches. The nutrient solution then flows down these growing benches and gravity feeds back to the central mixing tank.
Ebb and Flow Systems – A pump runs intermittently i.e. 4 times a day for 10 minutes each time to draw nutrient solution from the central tank and pump it out to above ground growing benches. The nutrient solution then floods these growing benches for a set period of time. The pump is then shut off and the solution drains from the tables via special valves and gravity feeds back to the central mixing tank.
In both situations the nutrient solution has an altered EC and pH state when it is returned to the mixing tank. I.e. the EC is lower and the pH has risen due to the feeding activity of the crop.
The grower then needs to replenish this solution with more A & B nutrient stock solutions or acid.
If too much time elapses between doses then the EC and pH will drift too far outside of the desired range for the crop. This will slow growth or result in nutrient deficiencies.
If a grower is dosing the tank manually it must be done at regular intervals and with sufficient patience to ensure the solution is well mixed before each additional dose to prevent overshooting your EC setpoint or, more importantly, to prevent the pH dropping too rapidly and damaging the root zone of the crop (root burn).
A recirculating system controller removes this risk by dosing in smaller, regular increments automatically. This safeguards the health of the crop, increases yield, and frees up the grower to focus on the more important aspects of their business.