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pH Explained

acids_01pH is a very important factor to the horticulture world because plants depend on the proper pH in order to uptake nutrients correctly.

pH measures the acidity or basicity of the feed water, soil or medium. pH is also a measure of the concentration of hydrogen atoms in a liquid solution. The pH scale ranges from 1 to 14, 7 being neutral; the lower the pH the more acidic the solution or nutrient is.

As the number of hydrogen ions decrease from a solution, pH climbs to a base level. Inversely, when the quantity of hydrogen ions increases in solution, pH drops indicating an increase in acidity. Each point change in pH, for example 6 to 7, is a ten-fold change in the pH of the solution.

Each nutrient manufacturer usually has a recommended pH value to feed nutrients at. As pH varies, so does the availability in the quantity of nutrients in a solution. This means at different levels of pH, a chemical like nitrogen can be too readily available to the plant creating a potentially toxic level of nitrogen. This effect occurs on all macro and micro nutrients, thus the importance of obtaining and maintaining a proper pH.

A pH of 6.5 allows all nutrients to be appropriately available for plants to absorb.

Low pH

  • decreases availability of nitrogen, potassium, sulfate, calcium, magnesium, pHospHorus, molybednum, copper, boron.
  • increases the availablility of Iron and manganese zinc

High pH

  • restricts availability of iron and manganese, copper, and zinc.
  • increases availability to possible toxic levels of calcium, magnesium molybendum

For more indoor,outdoor, and hydroponics information, please visit San Diego Hydroponics & Organics website.

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