Perhaps the most overlooked aspect of gardening is pH.
pH is very important in hydroponic as well as regular "soil" gardening. pH is measured on a scale of 1-14 with 7 being "neutral". Acids are lower than 7 and alkalis (bases) are above 7.
A plant grown in a hydroponic or soil garden must have a pH balance to the specific plant's optimal pH range or the plant will suffer. At best, if the pH range is not compatible with the plant, the plant will grow poorly, be more susceptible to disease, have lower yields or have blossoms that aren't as brilliant or fragrant. At worst, if the pH range is not compatible with the plant, "The Death Penalty" is the verdict. An unbalanced pH will cause a condition known as "nutrient lockout". This is a condition where the plant loses its ability to absorb some of the essential elements required for healthy growth.
When the pH of a plant is unbalanced and nutrient lockout occurs the plant mimics classic plant guide deficiencies or excesses due to certain elements being deprived from the plant. A good example is where a suffering plant has an unbalanced pH and is showing classic signs of a nitrogen deficiency; the leaves at the bottom of the plant are yellowed and falling off. So what do you do? Naturally you increase the amount of nitrogen in your nutrient solution even though it already has an adequate level. The problem is that your plant has nutrient lockout and can't absorb that nitrogen because of the unbalanced pH of the nutrient solution. The result is that your plant dies from nitrogen deficiency or is extremely stunted or stressed.
All plants have a particular pH level that produces optimum results. This pH level varies from plant to plant, but generally most plants prefer slightly acidic growing conditions (between 6.0 - 6.5), although most plants can still survive in an environment with a pH of 5.0 to 7.5.
Pure water has a balance of hydrogen (H+) and hydroxyl (OH-) ions and is therefore pH neutral (pH of 7.0). When the water is less than pure it can have a pH either higher or lower than 7.0.
When you are growing hydroponically checking and adjusting pH is a simple matter. Checking and adjusting pH when growing in soil is more complicated and involves other procedures not covered in this article. There are several ways to check the pH of the nutrient solution in your hydroponic system.
Paper test strips are the most inexpensive way to check the pH of a nutrient solution with liquid pH test kits costing a little more. Both of these products rely on a pH sensitive dye that changes color when dipped into or mixed with nutrient solution. The resultant color is then compared to a color chart to determine the pH range of the solution being checked. Both of these products are relatively inexpensive, but can be hard to read, because the differences in colors can be subtle thus making them somewhat inaccurate and are more for 'ball parking" your pH level. Other issues for color comparisons are affected by the nutrient solution being checked already being colored from the various nutrients and supplements added to the solution.
The most accurate way to check pH is to use a digital meter. Digital meters come in a huge array of sizes and prices and are very handy and easy to use. You simply dip the electrode into the nutrient solution for a few moments and the pH value is displayed on a LCD display.
Digital pH meters are very accurate and fast. They need to be cared for properly or they will quit working. The glass bulb electrode must be kept clean and wet at all times.
To ensure accuracy pH meters should be calibrated on a regular basis, as the meters can "drift". The tip needs to be stored in an electrode storage solution or in a buffer solution. The tip should never be allowed to dry out.
Several products used by the hobby gardener to adjust pH can be found at your local hydroponic supply store. The pH adjusters are diluted to a level that is reasonably safe and easy to use. Many of the products have phosphoric acid (to lower pH), and potassium hydroxide (to raise pH). Both of these chemicals are relatively safe, although they can cause burns and should never come in contact with the eyes.
Always add the nutrients and supplements to the water before checking and adjusting the pH of your nutrient solution. The nutrients lower the pH of the water due to its elemental makeup. After adding nutrients and supplements and mixing the solution, check the pH using. If the pH needs to be adjusted, add the appropriate adjuster. Use small amounts of pH adjuster until you get familiar with the process. Recheck the pH and repeat the above steps until the pH level is reached.
The pH of the nutrient solution will have a tendency to rise as the plants use the nutrients so the pH needs to be checked periodically (and adjusted as necessary). To start out I suggest that you check pH on a daily basis. Each system will change pH at a different rate depending on a variety of factors such as the type of growing medium used; the weather, and the kind of plants and even the age of the plants all affect the pH.
And you thought pH was just to keep your pools, spas, and hot tubs clear and clean smelling.
Don and Sandy Landers are owners of Dream Garden Hydroponics, LLC.