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pH & Soil

by Sunny Datko

What is pH?

The pH scale measures how acidic or basic a substance is. It ranges from 0 to 14. A pH of 7.0 is neutral. A pH less than 7.0 is acidic, and a pH greater than 7.0 is basic. Each whole pH value below 7.0 is ten times more acidic than the next higher value. For example, a pH of 4.0 is ten times more acidic than a pH of 5.0 and 100 times (10 times 10) more acidic than a pH of 6.0. The same holds true for pH values above 7.0, each of which is ten times more alkaline—another way to say basic—than the next lower whole value. For example, a pH of 10.0 is ten times more alkaline than a pH of 9.0.

Why care about pH?

In soils or growing media, pH strongly influences the availability of nutrients and the presence of microorganisms and plants in the soil. Certain plants require a particular pH range to enable the required nutrients to be consistently available to the plant. If the solution is too acidic or too alkaline it can cause “lock up” – a situation that restricts certain elements essential for growth from being absorbed by the root structure. This in turn reduces plant heath and performance. Deficiencies in the required elements become apparent in plant growth and can lead to crop failure.

pH & Your Soil

Outdoors, soils have a natural tendency to acidify, thanks to rainwater. You may have heard that acid rain is a form of pollution—and it is—but all rain is slightly acidic, with a pH of about 5. That’s because the hydrogen in rainwater reacts with the carbon dioxide in air to form carbonic acid. Extreme pollution can drop the pH of rain to 4.  Minerals in soils can also affect their pH. A chalky soil has plenty of calcium carbonate, a famous antacid, which buffers the pH of soil and keeps it from becoming acidic.

How do you test the pH of your Soil?

There are a few different ways to test pH levels in soil. The most accurate but also most expensive route is to use an electronic pH meter, such as the Bluelab Soil pH Probe. This is a device that is inserted into the soil and gives an accurate digital reading. If you want to do things a little more basic, you can use litmus paper. The downside of this method is that it doesn’t give you an exact pH reading; it merely tells you whether your soil is acidic or alkaline.

Bluelab Soil pH Probe

bluelab soil ph probe ph meterThis non-refillable soil pH probe is used to measure the pH levels of soil or media of cropping, pasture, containerized plants, home gardens, propagation culture, or anywhere that the soils pH requires testing.  This probe can be used for direct pH measurements in soils.   The soil probe is supplied with a ‘dibber’ – the green spear pictured to the right. The ‘dibber’ is inserted into the media/soil prior to inserting the pH probe to ensure no damage occurs to the probe tip from coarse soil particles or stones.

Main Features:

  • Fully waterproof
  • Supplied in a lockable protective case
  • Calibration solutions included
  • Simple push button calibration
  • Auto turn off function (extends battery life)
  • Large easy to read LCD display
  • Low battery indicator
  • 2 x Alkaline AAA batteries included
  • Lightweight and portable
  • 5 year Bluelab Guarantee (6 month guarantee for probe)

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