A soil test is essential to planning for that new garden or changing one to accommodate new conditions. At the
least, a test of the soil’s pH is necessary to determine the health and vitality of the ground into which you
plan to invest your landscape dollars.
Simply put, pH is a chemical term used to express hydrogen ionization in water. The term refers to potential
hydrogen and indicates the breakdown of water (H2O), normally a stable molecule, into a positively-charged
hydrogen ion and a negatively-charged hydrogen-oxygen molecule (HO).
The soil’s acidity or alkalinity is determined by this ionization. It occurs when the various minerals and
organic materials combine with water molecules forcing the soil to change its properties.
We measure this ionization on a scale from 0 to 14. Neutral soils are said to have a pH of 7, or midway up
the scale. Acid soils are those with a pH of less than 7, and alkaline soils are those with a pH above 7.
Soils with an extremely low pH – very acid soils – are said to be "sour" Conversely, soils with a high pH
are said to be "sweet."
So much for the scientific "jargon." What’s important to you is the knowledge that pH directly affects your
soil’s health. And your soil’s health, in turn, directly affects your plant’s health. And finally, your
plant’s health directly affects its susceptibility to disease and insects, which may require you to apply
pesticides which, in turn, may directly affect your health!
Most plants will not tolerate a soil with extremes in pH. The reason for this intolerance is because pH
affects the release of essential elements necessary for the plant’s growth and vitality.
Nitrogen (chemical symbol N) the element we hear about most often. It is the primary element that
affects productivity of plant life. That is, it is directly responsible for vegetative growth in plants.
Without nitrogen, the plant’s leaves lack their lush green color and growth is stunted. In soils with very
low or very high pH, nitrogen is "trapped" – a condition most plants cannot tolerate.
Phosphorous (P) is essential for strong roots, flower and fruit development, and resistance to disease.
It too can be trapped in soils that are excessively "out of neutral" in pH. Recent tests have shown many
soils have excessive amounts of phosphorous that has accumulated by excessive application of synthetic
fertilizers onto tight clay soils. One of the reasons for this accumulation is that these normally high
pH soils prevent the plant from using all the phosphorous that is available.
Potassium (K) is the third important element in soil health. Most often, plants us the form of
potassium known as potash or potassium oxide (K2O). Potassium is essential to the plant’s ability to create
sugars. It is also essential to the plant’s capacity to resist disease, survive cold temperatures, and
provide drought protection. It is less susceptible to variations in soil pH, but can be significantly
trapped when soils are at their extremes in alkalinity or acidity.
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