LaMotte STH Series - Manual (Page 9)

Potassium (Potash)
The role of potassium (potash) in plant nutrition is discussed in
the LaMotte Soil Handbook. For interpretation of test results, see
the LaMotte Soil Handbook and page 22 of this manual.
When present in large amounts, ammonia salts will produce a
precipitate similar to that produced by the potassium. If fertilizer
containing ammonia salts has recently been applied, or if the soil
pH is below pH 5.0, perform the Ammonia Nitrogen test (page
19) before performing the potassium test. A high ammonia
nitrogen test result will alert the operator to a probable false high
reading in the potassium test; actual potassium levels will be
somewhat lower.
It is important that the temperature of the test sample and the
*Potassium Reagent C (5162) be in the range of 20-27°C
(68-80°F). On warm days, prior to Step 3 below, cool both the
test sample in the Potash “A” Tube and the Reagent C contained
by placing them in cool water.
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