A Guide to pH and EC of Nutrient Solutions

In simple terms, these are the basics of ph and ec in your nutrient solution.

pH of the Nutrient Solution

pH is a measure of how basic or acidic a solution in terms of dissolved Hydrogen ion (H+) concentration. So why do you need to monitor and maintain the pH? The answer is simple – it determines the availability and absorption of nutrients by your plants. The optimal pH range of a hydroponic nutrient solution should be 5.5-6.3 and roots assimilate nutrients best within this range.

Consequences of pH Fluctuation

Problems crop up when the pH deviates from this range. If it drops below 5.5, then the solution becomes vulnerable to micronutrient toxicity. This happens because the acidic salts bind to the core nutrients (especially calcium and magnesium) which then become non-absorbent by roots. When the pH goes beyond 6.5 (too basic), the micronutrients and other nutrients precipitate and accumulate on the walls of the reservoir and the growing medium. If the nutrients precipitate out of the solution, plants cannot absorb them. In short plants are stressed when pH is incorrect. That was the significance of monitoring pH for growing high value crops.

Adjusting pH

The pH is adjusted with the help of a pH meter. You can buy a kit for this purpose. Read the instructions explained in the manual before using the pH meter. Make sure that you have mixed the nutrients properly with water before checking the pH. Dip the pH meter in the nutrient solution and observe the readings. If the pH is higher than the desired level, then add either phosphoric acid or sulfuric acid to lower it. Similarly, if it’s lower than the desired level, then you need to add potassium hydroxide to raise it. Add the acid or the alkali solution very carefully in order to achieve the accurate range without much effort. It is quite possible to not get the ideal range in the first chance and for this you need to practice the technique of adding the acid or alkali to a spare solution. You need to monitor the pH frequently in a closed system because the same solution is recycled to your plants.

CF/EC/TDS of the Nutrient Solution

  • CF: Conductivity Factor
  • EC: Electrical Conductivity
  • TDS: Total Dissolved Salts

CF is the capacity of the solution to conduct electric current. Simply put, EC measures the level of fertilizer salts present in the nutrient solution. The strength of the nutrient solution is measured either by an EC meter, CF meter or a TDS meter. The units used for measuring these values are PPM (Parts Per Million), µS (MicroSiemens) and mS (MilliSiemens). Your high value crop grows happily within 0.75 to 1.5EC and TDS 500-1000ppm. Growth rate of plants gets affected adversely if the EC fluctuates from this range. Electrical conductivity of a nutrient solution is largely dependent on temperature (68-78 degree F).

Another important aspect that you must check is the calibration of the EC, CF and TDS meter. Read the instructions carefully and then use it. Also ensure that it is water resistant, energy efficient and has good quality of electrodes and batteries.

Fluctuation of EC

If the EC goes beyond the normal range, then the root zone of the plants will be damaged severely. Therefore, it is suggested to begin with a relatively weak solution so that the EC remains within the normal range even if the water evaporates.

EC values in different stages of Growth

  • Transplantation of seedlings: 500-600ppm
  • Peak vegetative growth: 800-900ppm
  • Transition from early to heavy flowering: 1000-1100ppm
  • Flushing or Harvesting: 400-500ppm

The bottom line is using an EC meter along with a pH meter helps determine the optimum nutrient dose of plants without over fertilization. And therefore you must maintain the optimum values throughout growing.

9 thoughts on “A Guide to pH and EC of Nutrient Solutions

    • Vanessa says:

      Hello Mike,

      The ppm scale is 500, sorry you were unable to reach anyone and for the inconvenience. Feel free to email us at any time with any questions you have. Have a wonderful day!

    • Ty Harvest says:

      Hi Stephen,
      pH 7 is defined as neutral, below 7 is acidic and above 7 is alkaline. Pure water is pH 7. For many hydroponic plants, including cannabis, the optimal pH range is between 5.5 and 6.5. In soil, you want a pH level that is slightly acidic or between 6.0-6.5.

  1. BC Stargazer says:

    Do you ad the calmag to the reservoir with the A&B, honeychome, etc..? Or are you supposed to use the calmag by itself with just plain water? The instructions say “water days only” seems vague, What’s that mean exactly? How can you use it without water? Same question for the strudy stalk. Having serious issues with the Emerald Harvest nutrient line up.

    • erik.barton says:

      Hello BC Stargazer,

      Yes Cal-Mag can be added to the reservoir with all or even some of the other additives and should not cause any issues. Typically Cal-Mag is only recommended as a supplement if you are feeding your plants and beginning with RO water. Sturdy Stalk can also be added as a supplement with all or even some of the other additives but it should always be mixed with the water first before the other additive. We are currently in the process of updating the feeding chart to clear up some of the confusion.

      – Emerald Harvest

    • Ty Harvest says:

      No – actually with our nutrients being so clean and chelated, they absorb very well into the plant. So residuals are extremely low and not noticeable – we usually don’t recommend flushing. But you may do as you please – just don’t waste King Kola or Honey Chome by adding during flushing as there is no need. Thnx.

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