If you’re flushing your system and replacing the nutrient at least once every 2 weeks, you’re probably managing the PH levels quite effectively, however, it’s worthwhile going to the next level if you want to get the best results.
Get yourself any ordinary pool chemical test kit, and test the PH level once p/week.
The optimal PH range is between 5.2 – 6.2
How to minimize pH fluctuation in recirculating systems1. Use a nutrient brand that is highly pH buffered, particularly when using very alkaline water.
2. Supply at least 10 litres (2.5 gal) of nutrient for each large plant. Failure to do this will magnify pH (and EC) fluctuations, especially during hot and dry weather when water uptake and evaporation are both excessive. To avoid excess water uptake and high evaporation rates, keep the air temperature below 30OC (86OF) and relative humidity above 50%.
How to adjust pHStep 1. Measure the pH: Use either a liquid pH indicator or an electronic pH meter. Before measuring the pH, ensure that the nutrient is well stirred and that the sampling container is clean.
Step 2. Choose a target pH: It is inconvenient and unnecessary to hold pH at a single point value so choose a target pH that provides both a safety margin and minimizes the amount of pH maintenance. For example:
– If your pH tends to continuously rise (the most common trend), then at each adjustment, reduce the pH to about 5.0 using pH Down. This will give you a much larger pH “safety” margin than, for example, 5.8.
– If pH tends to fall, at each adjustment increase the pH to about 6.0 using pH Up.
Step 3. Adjust the pH: Add a small amount (e.g. 1ml per 50 litres) of pH Down / pH Up. Then stir well and check pH. Repeat this process until the target pH is reached. When using pH Up, ensure to pre-dilute the dose at least 100-fold with water before adding to the nutrient.
Adjusting pH by trial-and-error can be tedious, especially for large reservoir volumes. Refer to Note 1 for an alternative method.
Pre-adjusting the pH of water
Do not pre-adjust the pH of raw water before adding nutrient unless the make-up water has high alkalinity. If you do attempt this procedure, because natural waters have a low buffering capacity you will typically get wild pH swings either side of the pH target without ever landing on the target value.
Note that the pH values being discussed in this chapter are the values of the working nutrient solution – not the make-up water.
The pH of the nutrient solution is a major determinant of nutrient uptake by the plant. If the pH wanders outside the optimum range of between pH 5.1 and pH 6.2, then nutritional deficiency and/or toxicity problems can occur. For hydroponic nutrient solutions used with inert media, keep the pH at 5.2-5.5 for optimal elemental uptake. It is at this point that roots most readily assimilate nutrients. These pH and TDS/EC recommendations may seem low relative to the normally suggested range, but are based upon information garnered from “Hydroponic Nutrients” by M. Edward Muckle and Practical Hydroponics and Greenhouses. They both document the low pH resulting in increased nutrient uptake and my experience has shown discernible health and yield improvements at a ph of 5.2 over higher levels.