LaMotte MAGNESIUM & MANGANESE SOIL TESTS MODULE C - Manual (Page 2)

EX TRAC TION PRO CE DURE
1.
Fill a test tube (0755) to line 7 with *Universal Extracting Solution
(5173).
2. Use the 0.5 g spoon (0698) to add four level measures of soil to the
test tube. Cap and shake for one minute.
NOTE:
When adding samples with high concentrations of
carbonates to *Universal Extracting Solution (5173), swirl tube to
mix for 30 seconds before capping to allow gases to escape.
3. Fold a piece of filter paper (0465) in half, then in half again. Press
corners together to form a cone. Place in funnel (0459). Pour
extract solution into funnel, collecting extract. This clear extract is
used for the test.
MAG NE SIUM TEST
1.
Use a transfer pipet (0364) to add ten drops of soil extract to a
large depression on a spot plate (0159).
2. Add one drop of *Magnesium Test Solution (5140). Stir with a
stirring rod (0519). Solution will turn pale yellow.
3. Add one drop of *Manganese-Magnesium Solution #2 (5145WT).
Stir with a stirring rod. Compare to color standards on Magnesium
in Soil Color Chart (1306). Continue adding *Manganese-
Magnesium Test Solution #2 one drop at a time until sample color
matches a color standard. Record as ppm Magnesium.
NOTE:
It usually requires 2 drops of *Manganese-Magnesium Test
Solution #2 to cause color change.
IN TER PRE TA TION OF MAG NE SIUM TEST
Soils giving a very low test should be treated with dolomitic lime or
fertilizers, such as double-manure salts, which contain considerable
magnesia. Soils giving high, or very high, magnesium tests, with low
calcium tests, should receive applications of gypsum or high calcic lime,
in order to prevent calcium deficiency, due to over-balance of
magnesium.