pH in a Hydroponic System

 
Balancing the pH in your hydroponics system is incredibly important to the health and vitality of your crop. If the pH is not in the correct range then essential nutrients and micro nutrients will not be available for uptake by your plant. This can lead to nutrient deficiencies and eventually death.
 

The definition of pH

 

pH

piːˈeɪtʃ/
noun CHEMISTRY
       

    1. a figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline. The pH is equal to −log10c, where c is the hydrogen ion concentration in moles per litre

       
      Less technically, it is the potential hydrogen-hydroxyl ion content of the solution. Solutions ionise to positive (hydrogen) and negative ions (hydroxyl) bonds. If the solution has more positive ions in the solution then it is said to be acidic, and has a pH in the range 1-6.9. If the solution has more negative ions in the solution then it is said to be alkaline, and has a pH in the range of 7.1-14.
       

      So why is pH Important?

       

      PlantpH Range
      Asparagus
      Basil
      Beans
      Broccoli
      Cabbage
      Carrots
      Cauliflower
      Chives
      Cucumbers
      Garlic
      Ginger
      Leek
      Lettuce
      Onions
      Peas
      Pumpkin
      Strawberries
      Tomatoes
      6.0-8.0
      5.5-6.5
      6.0-6.5
      6.0-6.5
      6.5-7.5
      5.8-6.4
      6.0-6.5
      5.5-6.5
      5.8-6.0
      6.0-6.5
      6.0-8.0
      6.0-8.0
      6.0-6.5
      6.5-7.0
      6.0-7.5
      5.0-6.5
      5.5-6.5
      5.5-6.5

      If the pH levels are outside of the optimum range then the plants will lose the ability to absorb some of the essential elements required for steady growth.

      The optimum pH levels of plants varies, with most preferring slightly acidic growing conditions – although most can survive in the range (5.0-7.5). A few commonly grown hydroponic vegetables and their optimum pH range are listed to the right and shows the variation in levels.

      Above pH 6.5 many nutrients and micro nutrients precipitate out of solution and stick to the walls of the hydroponic reservoir.

      In order for your plants to feed from the nutrients you are adding they need to be dissolved in solution. In the event of the nutrients precipitating out of solution your plants are unable to absorb them and suffer nutrient deficiencies if not quickly corrected.

      The availability of these nutrients and minerals can also be effected by in increase in pH levels. A chart can be seen below indicating the availability of different nutrients to plants at varying pH levels.
       

      nutrient availability in plants pH

       

      Testing the pH of your System

       
      So we know that the pH levels of your hydroponic nutrient solution is extremely important in order to keep the right availability of nutrient uptake for your plants. But how do you go about testing the pH levels of the solution?

      There are a number of options, ranging from the cheap & inaccurate to the expensive and highly accurate measurements.

      The cheapest option is to use a paper test kit, this is a strip of litmus paper – a water soluble mixture of different dyes extracted from lichens, that when dipped in your solution will change colour. This colour is then compared to a colour comparison chart to determine the correct pH level. These kits are throw away and very inexpensive, however due to the slight discrepancies between colours it can prove to be difficult to judge the correct levels.
       

      pH litmus test

      pH litmus test


       
      Liquid test kits can also be used, they work through a similar colour comparison method – a few drops of solution are added to the liquid test kit and the colour compared. These kits are more popular as the offer greater accuracy in the interpretation of results.

      ph Dosing pumpThe most popular choice among hobby indoor gardeners is the use of a digi pH pen, these meters are accurate with a digital read out, though you will need to calibrate regularly.

      Automatic pH meters are the most accurate when calibrated correctly and offer continuous monitoring often with the possibility of data logging and taking into account temperature fluctuations, which can effect the calculation of pH levels.
       

      Adjusting the pH of your Hydroponic Solution

       
      Using a pH up and down solution in small quantities allows for the control of the pH in your reservoir. Levels should always be checked after nutrient solutions have been added to the reservoir as they contribute to changes in the pH levels.

      pH adjusters can be added manually or automatically using a pH dosing pump.

      The automatic pH dosing pumps allow for the continuous and automatic control of the pH level in your hydroponic solution. Once calibrated the pumps pH measuring probe is added to the solution and starts measuring the pH levels. The pH range is programmed into the pump and whenever the probe detects the solution being out of the range it will begin adding pH up or down to correct the levels and bring back into a safe operating zone.
       
      pH automatic dosing set up
       

      How Else can you Improve Nutrient Uptake?

       
      You can improve nutrients uptake in your plants by using Humic an Fulvic acids. Easy Grow stock a range of humic acids and fulvic acids to aid the uptake of nutrients in your plants, chelating valuable minerals and making them more readily available to your plants. Green Planet Nutrients GPH and GPF is humic acid and fulvic acid in solution, ready mixed to add to your reservoir. RAW Humic and Fulvic acids are water soluble powders available to dilute in solution and add to your reservoir.  Follow the links to learn more about these fantastic products.
       
      GPF UptakeGPHRaw Humic Acid GroupRaw Full Up Group
       
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