Soil pH Earth
Country: United States
Date: November 2006
What is soil PH? Is it better for the ph to be
high or low.
pH is a measure of soil acidity. Low pH soils are acid and high pH
soils are basic. Soils east of the Mississippi river tend to be acid
while those to the west tend to be basic. The pH controls what minerals
are available for plant growth. Basic soils, for example have less iron
available. Wild plants have adapted to varying soil pH as a way of
For the gardener, soil pH is of great concern depending upon what they
are trying to grow. I have often added ground lime to soils to make
them more basic, or "chelated sulfur" to turn them more acid. Of
course, I move around a lot, too.
The pH is the logarithm of 1/[H+] where [H+] is the concentration of
hydrogen ions. So it is a measure of how acidic or basic a solution is. Low
values: 0 to 7 are acidic. High values 7 to 14 are alkaline. With regard to
which is "better" depends upon what the soil is intended to do. Some plants
grow better in somewhat alkaline conditions. Other plants grow better in
somewhat acidic conditions. So there is no universal "good" or "bad". It
depends upon what the use of the soil is.
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Update: June 2012