LaMotte STH Outfit - Manual (Page 12)

12
Magnesium
Magnesium is a constituent of chlorophyll, and chlorosis can result from
magnesium defi ciency. Like calcium, magnesium cations play a role in
base or cation exchange. Magnesium is subject to more leaching than
calcium. Soils giving a low test reading should receive dolomitic lime
or fertilizer which contain considerable magnesia. Soils giving high
magnesium tests and low calcium tests should receive gypsum or high
calcic lime, in order to restore the calcium-magnesium balance.
PROCEDURE
1. Use a transfer pipet (0364) to transfer ten drops of the general soil
extract to one of the larger depressions on a spot plate (0159).
2. Add one drop of *Magnesium Test Solution 1 (5140). Stir with
a clean rod (0519). A pale yellow color will develop.
3. Add *Magnesium and Manganese Test Solution 2 (5145WT) one
drop at a time with stirring, until the pale yellow color changes to
one of the darker shades indicated on the Magnesium Color Chart
(1306). About two drops are usually required. Under some conditions,
a precipitate will form shortly after *Manganese-Magnesium Test
Solution #2 has been added. This will not effect the test reading.
The test result is expressed in relative values of Magnesium from
very low to very high. For approximate corresponding value in parts
per million or pounds per acre, see page 19.