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PH is an indication of the acidity or alkalinity in a medium. It is measured on a scale of 0-14, 0 being extremely acidic (think more acidic than stomach acid), and 14 being extremely alkaline (think more alkaline than ammonia or lime). The effect of pH is huge on the solubility of minerals or nutrients. Since 14 out of the 17 essential plant nutrients are obtained through the root zone, they must be dissolved, and soluble for proper uptake. Most of these are more available in acidic conditions than neutral and alkaline environments. The ideal pH for plant nutrient uptake is between 5.5 and 6.5. It is important to understand that it functions on an logarithmic scale, which means that from a pH of 1 to a pH of 2 there is a 10 fold increase.; thus, making testing all the more important.
Because of the specific requirements for proper mineral uptake it is important to test the pH pf three things: your water, your fertilizer solution and your growing medium. Litmus paper, and pH drops are reliable enough for generalizations and maintaining a healthy system. However, if a problem is noticed, then a more accurate method should be employed. A high quality pH meter can be used to test water, fertilizer solution, as well as growth medium. The most popular tool used to test pH is BlueLab pH Pen because of its versatility and ease of use. We also suggest the Myron L Ultrapen PT2 for the most accurate reading. Unlike its competitors it reads the pH to the hundredths place, which can be very important when you consider that pH is a logarithmic scale. For a more in depth look at your solution’s total dissolved solids, we suggest the BlueLab Combo Meter. This meter measures pH, EC, has a replaceable probe and a 5 year warranty.
In fertilizer solutions, using a pH up or down solution may be required in order to achieve the preferred acidity or alkalinity. PH up generally consists of Potassium Bicarbonate and/or Sodium Bicarbonate. PH down is most popularly Phosphoric Acid and/or Citric Acid. The ingredients of the pH solution used, as well as the ingredients of the nutrient solution will determine short term and long term stability of the pH of the solution. Bicarbonates can have long lasting effects on the media environment and should be used in hydroponic gardening, or very sparingly for soil. In soil, Dolomite Lime should be the go-to ingredient for long term pH stabilization. Phosphoric Acid, which is ideal for hydroponics, can keep solutions stable for much longer than a Citric Acid based pH solution, but may not be better to acidify a soil grow. One of our favorite organic pH adjusters is Earth Juice DoubleUp and Earth Juice DoubleDown.