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

ALUMINUM TEST
1. Use the transfer pipet (0364) to add two drops of clear fi ltrate 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).
INTERPRETATION OF ALUMINUM 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 benefi ted 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.
SULFATE TEST
1. Use the transfer pipet (0364) to add fi ve drops of clear fi ltrate 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.
INTERPRETATION OF SULFATE TEST
Plants obtain the sulfur which they require from the sulfates in the soils. Sulfates are
usually present in the soil, although a defi ciency 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.