LaMotte Soil Chemistry Test Equipment - Manual (Page 6)

SOIL pH
The pH scale is a numerical system used to measure the acidity of
alkalinity of a soil. Plants will not thrive on soil that is either too acid or too
alkaline because the soil pH directly affects the availability of mineral
nutrients which plants need for optimum growth. For example, if the pH is
too low, phosphates may be chemically bound and not readily available to
the plant and bacterial action responsible for the production of nitrates
may be reduced. The key to good crop production is to maintain the pH
within the range where plants and microbiological activity can function at
their most efficient level.
To simplify the classification of plants according to their soil pH preference,
they have been divided into two main groups. Those plants preferring soils
whose pH is within the neutral range, 6.0 to 8.0, are placed in Group A.
Plants preferring slightly acid soil are placed in Group B, range 5.0 to 6.0.
Acid
(Sour) Neutral Alkaline
(Sweet)
3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
Group B
Plants
Group A
Plants
The Plant-Soil Preference List indicates pH preferences for over 100
common plants. Since most garden hobbyists cultivate a variety of plants,
achieving optimum soil conditions may involve using a different treatment
program in different areas of a lawn or garden. It is important to establish
distinct sampling areas, so that test results may be interpreted in terms of
the plants to be grown in each area.
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