Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001631
11/12/99

Soil pH problems


Soil pH determines the availability of the nutrients in
the soil solution. Some plants, such as rhododendron or
azalea, have difficulty absorbing iron unless the soil pH
is between 4.5 and 5.5. Pin oak and holly will show iron
deficiency symptoms at a pH above 7.5. On maples,
manganese deficiency is more common than iron deficiency

Correcting a high soil pH over the entire area of a tree's
root zone may not be worth the effort. Maintaining a low
pH for a small number of shrubs is more feasible.

Lower the pH by applying sulfur. Use the table as a guide
for sulfur rates. You need to know the existing pH and
the soil type to use the table properly.

Quantity of sulfur required to reduce soil pH for a
depth of 7 inches.
--------------------------------------------------------
Desired pH Sands Sandy Loams Loams Clay Loams Organic
Change -----------lb sulfur/100 square feet-----------

7.0-6.0 0.7 1.2 1.6 2.5 3.9
6.0-5.0 1.8 2.8 3.2 3.2 6.3
5.0-4.0 1.8 2.8 3.2 4.1 10.3
----------------------------------------------------------

Avoid sulfur applications to lawns during hot weather to
minimize the possibility of burning the grass.

Other materials, such as aluminum sulfate, are also used
to reduce soil pH, but more of the alternative materials
is needed to obtain the same change in pH.


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