LaMotte IRON, ALUMINUM, & SULFATE SOIL TESTS MODULE D - Manual (Page 3)

ALU MI NUM TEST
1.
Use the transfer pipet (0364) to add two drops of clear filtrate to a
large depression on the spot plate (0159).
2. Use a plastic pipet (0352) to add two drops of *Universal
Extracting Solution (5173).
3. Use a second plastic pipet (0352) to add one drop of *Aluminum
Test Solution (5101). Stir with a stirring rod (0519). Wait one
minute.
4. Match sample color to a color standard on the Active Aluminum
Color Chart (1301).
IN TER PRE TA TION OF ALU MI NUM TEST
Aluminum occurs in large amounts in all soils in the form of
undecomposed minerals, and in the inorganic colloidal materials. In
neutral, slightly alkaline or slightly acid soils, the element is in inert
combinations that have no effect on plant growth. At greater degrees of
acidity, aluminum becomes active, capable of combining as soluble salts,
and thus exerting a toxic effect upon the growth of many plants,
especially those that are benefited by liming, when grown on acid soils.
A high, or very high, test is a certain index of an undesirable acid soil,
upon which acid-sensitive crops are almost certain to fail. A medium
test is not so serious, especially with grasses, corn, oats, potatoes and
tobacco. A low, or negative, test is desirable, except for distinctly
acid-tolerant plants.
SUL FATE TEST
1.
Use the transfer pipet (0364) to add five drops of clear filtrate to
turbidity vial (0242).
2. Use capped pipet (0392) to add one drop of *Sulfate Test Solution
(5171). Gently swirl to mix.
3. Lay Sulfate Color Chart (1314) under neutral light. Hold turbidity
vial one-half inch above black strip in middle of chart. Look down
through turbid sample. Match sample turbidity to a turbidity
standard. Record as ppm Sulfate.
IN TER PRE TA TION OF SUL FATE TEST
Plants obtain the sulfur which they require from the sulfates in the soils.
Sulfates are usually present in the soil, although a deficiency may exist
in some localities. Unless present in excessive quantities, sulfates are not
harmful to plants. High tests may indicate recent addition of sulfur or
sulfate compounds to soil.