Why Is My Runoff pH So High?
Everyone knows that the pH of a nutrient solution has a fairly strong effect on plant development. Experienced hydroponic experts constantly measure and maintain the optimum pH in their hydroponic systems, and yet sometimes it rises and falls. Why is this happening and how to deal with it? Let’s find out!
Reason 1: High Water pH
The water used to prepare the nutrient solution can have different acidity levels. For example, distilled water, which many people prefer to use, has a pH of 7 units. And the solution is prepared based on this indicator. Meanwhile, in 3-4 hours the pH will drop to 6-5.5 because CO2 has got into the water.
As for tap water, it contains calcium and magnesium salts. When carbon dioxide reacts to such water, the acidity of the solution can change unpredictably. The best way to clean up your tap water is through a process called reverse osmosis. Special adjusters can also be used, but the addition of chemicals can affect the plants, especially young seedlings.
Reason 2: Fertilizers
Many fertilizers contain substances that can influence the acidity of the solution. For example, when calurea is added to a fertilizer, ammonia molecules get into the solution and change the pH level. The amide bond typical for some compounds impacts the acidity of the solution in the same way. In addition, the indicators change when the plant absorbs nutrients. When some ions are absorbed, the pH level falls; when others are absorbed, it increases.
Reason 3: Substrate
Many hydroponic systems (Ebb&Flow, Drip irrigation, Nutrient Film Technique) use one or another substrate. It can be expanded clay, vermiculite, peat, mineral wool, and coconut substrate. And each of these fillers has a different pH level, which affects the acidity of the nutrient solution as well.
How to Stabilize the pH in a Hydroponic System?
Phosphates are often used to stabilize pH. However, sometimes they turn out to be too weak. In addition, such stabilizers can damage plants, since the pH of the plant itself is much higher than that of the nutrient solution, and is usually equal to 7.0-7.2. But new, young roots have a pH of about 4 units. Rough handling of buffers and stabilizers can destroy the plant’s optimal acidity and the optimal root acidity. As a result, the plants die.
When using fertilizers or different substrates, it is still possible to maintain the pH level, if you carefully consider the EC of the solution. If the EC of the water is in the range of 100 ppm, then it is quite possible to keep the pH values at an optimal level.