4 Things About pH

Techno speak says that "pH" is a unit of measure which describes the degree of acidity or alkalinity of a solution. It is measured on a scale of 0 to 14, with 7 on that scale being neutral.

The term pH is derived from "p", the mathematical symbol of the negative logarithm, and "H", the chemical symbol of Hydrogen. The formal definition of pH is the negative logarithm of the Hydrogen ion activity. A little simpler and easier to remember is that the "p" stands for "potential" and "H" means Hydrogen. So that pH means the potential of hydrogen to do its thing, which is to facilitate the transfer of ions easily or not. Wow!

In even simpler terms, that means that pH is a scale (like yards on a football field) to understand the relationship between alkalinity or acidity. On the scale, "0" is the most acidic and "14" is the most alkaline. Neutral is pH 7, or in the football terms, on the 50 yard line. From your fabulous seat on the 50, the end-zone to your right is ACIDS and to the left, it is the ALKALINES. Go team go!

pH and soils

Soils generally range from an extremely acidic pH measurement of 3 to a very alkaline pH of 10. Most plants that we might have in our landscape like a slightly acidic condition with a pH around 6.5. Some plants including rhododendrons, azaleas, blueberries, like a very acidic pH of 4.5 — 5.5.

How does a soil's pH effect a plant?

While the up or down pH measurement doesn't directly effect plants, it does create situations in the soil that effects the long term vitality of a plant. Depending on the soil's pH, determines how soil nutrients become available or unavailable.

For example, if you look at a young leaf and notice a yellowing between the veins of that leaf, this is an indication of iron deficiency in the plant. Not necessarily a deficiency of iron in the soil, but a problem with the plant to absorb the available iron because the soil's acidity is too low. The low acidity, or low pH, won't allow the transfer of ions through a particular plants molecular root structure. When the proper acidity level is reached for that plant, the chemical reaction can occur and the transfer is able to be completed.

How do you change the pH to suit your plants?

Before making any changes, you must know your soil's current level. This will determine how much is needed to raise or lower the pH, if at all. Soil tests can be done at home, a private soil-testing laboratory, or your local county extension office. This will give you an accurate measurement of your soil and how you need to adjust it to bring it in to an optimal reading.

Limestone is used to raise the pH and sulfur lowers it. Both of these elements are available in pelletized form which is easy to apply with a lawn spreader. Avoid using the powders.

Why monitor the pH?

Ideal pH for the plants you are growing requires regular monitoring to maintain that levels. Soils that are naturally alkaline or acidic will tend to go back to those levels over time. Fertilizers applied to the beds can also cause shifts in the pH. Do the soil testing every few years or so.