Last Updated on July 12, 2020
Hydroponics is an extremely popular way of growing plants without using soil. Instead of soil, hydroponic cultivation involves using a water solvent containing mineral nutrient solutions. Experts suggest that maintaining precision is extremely important for a successful hydroponic project.
Various factors have a significant impact on plant health within a growing system. These factors include crop selection, design of the system, humidity, temperature, pH, and many others. In order to achieve optimum results, parameters such as humidity, temperature, pH, etc. must be maintained within a specific range.
In this discussion, our focus will be on the nutrient solution’s pH in hydroponics.
What is pH?
The term pH may be defined as a logarithmic scale used for expressing any solution’s acidity or alkalinity. The measurement is done on a scale of 0-14, with 7 being the neutral value. Anything above 7 is alkaline and less than 7 is acidic. As the pH scale is logarithmic, pH 5 refers to ten times higher acidity compared to pH 6.
Measurement of pH:
There are many convenient ways to measure the pH of a solution.
- Test strips: These paper strips have a coating of special compounds capable of changing the color when they are dipped in a solution, depending on its acidity or alkalinity. The kits come with a color chart that is used to determine the pH of the solution by comparing the strip’s color with it.
- Test Kits: The testing kits comprise of a pH test indicator solution. The pH of the test solution is determined by adding a few drops of the indicator solution to the sampling solution. A comparison between the color chart provided with the kit and the coloration of the solution determines the pH of the test solution.
- pH Meter: These digital instruments are dipped in the solution to measure its pH. Though relatively expensive, this method provides higher accuracy and is easier to use.
Importance of pH in Hydroponics:
In hydroponic cultivation, the solubility of the nutrient salts, as well as the uptake of nutrients by the plants, is determined by the pH of the nutrient solution.
For example, if the pH goes beyond the range of 5.5-6.5, the amount of iron received by the plants is reduced. This may lead to iron deficiency, even if it is present in the solution. Higher pH also leads to calcium deficiency because it precipitates into an insoluble form.
The availability of all essential nutrients is fairly optimal within the pH range of 5.5 to 6.5 for almost all plants. Any deviations either way may lead to a deficiency in terms of one or more essential nutrients.
Adjusting pH in Hydroponics:
Adjustment of the pH of the nutrient solution is essential for achieving the optimal range for the plants being grown. Naturally, this is done by increasing or reducing the pH of the solution.
Please remember that hard water is resistant to pH changes in the solution due to the presence of carbonates. On the other hand, soft water offers almost no resistance to pH change.
- Acid Addition: When an acid is added to the nutrient solution, its pH comes down. Therefore, if the solution has a pH higher than the desired range, a suitable acid can be added to bring it to the right range. Though any acid can be used from a technical standpoint, it is important to opt for one that is safe for the plants as well as people handling it. In general, a 2-5% solution of phosphoric acid is considered to be the best option for this purpose.
- Alkali Addition: If the pH of the nutrient solution is less than what is required, an alkali can be added to achieve the desired range. Out of all types of alkalis, potassium hydroxide is widely used because it also provides potassium to the plants.
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