LaMotte STH Series - Manual (Page 17)

Aluminum
All soils contain significant amounts of aluminum in inorganic
colloidal material and in the form of undecomposed minerals. In
neutral, slightly alkaline, or slightly acid soils, this aluminum is in
inert combinations that do not affect plant growth. In more acidic
soils, aluminum can form soluble salts toxic to plant growth. A
high test result indicates an undesirable acid soil. Plants which
normally thrive on acid soils may fail on a soil with a high active
aluminum test reading. A medium test result is generally tolerable
- especially for grasses, corn, oats, potatoes, and tobacco. A low or
negative aluminum test result is preferable.
Procedure:
1. Use a transfer pipet (0364) to transfer two drops of the
general soil extract to one of the larger depressions on a spot
plate (0159).
2. Add two drops of *Universal Extracting Solution (5173).
3. Add one drop of *Aluminum Test Solution (5101).
4. Stir with a clean stirring rod (0519). Allow to stand for one
minute.
5. Match the resulting color with the Active Aluminum Color
Chart (1301). The test result is expressed in relative values of
active aluminum from very low to very high. For approximate
corresponding values in parts per million or pounds per acre,
see page 22.
15