LaMotte STH Outfit - Manual (Page 10)

10
Phosphorus
The role of phosphorus in plant nutrition is discussed in the LaMotte
Soil Handbook. For interpretation of test results see the LaMotte Soil
Handbook.
The Phosphorus test is extremely sensitive. Special precautions should
be taken to prevent contamination. In particular, exposure of the test
components to fertilizer dust must be scrupulously avoided. The operator’s
hands and clothing, the work surface, and the testing area in general
must be clean and free of fertilizer residues.
LaMotte offers the Model NF Test Kit (Code 5090) for Phosphorus in
Alkaline Soils, to be used in place of the test described below when the
soils are predominantly alkaline (above pH 7.0).
PROCEDURE
1. Use a transfer pipet (0364) to fi ll a “Phosphorus B” Tube (0244) to
the line with the general soil extract.
2. Add 6 drops of *Phosphorus Reagent 2 (5156). Cap and shake
to mix.
3. Add one *Phosphorus Test Tablet (5706A). Cap and shake until
dissolved.
4. Immediately compare the color that develops in the test tube against
the Phosphorus Color Chart (1312). Hold the tube about one inch in
front of the white surface in the center of the color chart. View the
chart and sample under natural light for optimum color comparison.
The test result is read in pounds per acre
Available Phosphorus.