In hydroponics, the pH level of a nutrient solution can become essential for proper plant growth. Each species of plant has its ideal pH level. The availability of essential nutrients and elements for that plant is also dependent on pH.

As pH increases, elements such as iron, manganese and zinc can precipitate out of solution and become unavailable to the plants. Even if your nutrient solution has the ideal concentration of these elements at high pH, the plants may not absorb them, resulting in a deficiency. To overcome this problem, many advanced plant fertilizers incorporate special chelating agents which ensure that iron and other nutrients remain in the solutions at higher pH levels.

The few elements like phosphorous and molybdenum can become unavailable to plants at low levels of pH, and when the pH dips below 5.0, there is also a danger of root burnings and the destruction of root tissue.

Levels of pH are easily corrected through the addition of either alkaline or acidic solutions. The diluted solution of potassium hydroxide (KOA) it is commonly used to raise the levels in hydroponic nutrient solutions. Phosphoric acid and nitric acid are commonly used to lower levels of pH. Add diluted pH adjusters slowly over time to a well mixed nutrient tank.

Ideal pH Ranges for Hydroponic Plants

Lettuce

      5.6 - 6.2

Tomatoes

      5.7 - 6.1

Strawberries

      5.9 - 6.3

Peppers

      5.8 - 6.3

Beans

      5.7 - 6.3

Cucumbers

      5.7 - 6.1

Basil / Herbs

      5.6 - 6.1

Melons

      5.4 - 5.6

Cabbage

      6.3 - 6.6

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