| Chapter 12 |
| PH |
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PH is the measure of acid-alkalinity balance of a solution. It is measured on a scale of 1-14 with 1 being most acidic. 7 is neutral and 14 is most alkaline. Most nutrients are soluble in a limited range of acidity from about 6-7. Should the water become too acid or alkaline, the nutrients dissolved in the water precipitate and become unavailable to the plants. When nutrients are locked up, the plants cannot grow. Typically, a plant growing in an environment with a low pH is very small, often growing only a few inches in several months. Plants growing in a high pH environment will look pale and sickly and also have stunted growth. PH is measured using aquarium or garden pH chemical test kits pH paper or a pH meter. PH meters are the most convenient to use. The probe is placed in the water or medium and indicates pH. These items are available at plant stores and hi-tech garden centers and are easy to use. Once the water is tested gardeners adjust it if it is not in the ideal range of 6.2-6.8. Hydroponic supply companies sell pH adjusters which are convenient and highly recommended. The solution can also be adjusted using common household chemicals. The pH of highly acidic solutions can be raised using bicarbonate of soda, wood ash or hydrated lime. Alkaline water can be adjusted using nitric or sulphuric acid, citric acid or vinegar. Once a standard measure of how much chemical is needed to adjust the water, the process becomes fast and easy to do. Plants affect the pH of the water solution as they remove various nutrients. Microbes growing in the medium also change the pH. PH is adjusted whenever the water is changed or added. Since the medium and plants affect the water’s pH, growers often take a pH reading of the water after it has passed through the system. Water passing through a low pH medium can be adjusted upwards. High pH mediums such as rockwool are often irrigated using low pH water. Step By Step
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