LaMotte SMART 2 Electronic Soil Lab - Manual (Page 74)

PROCEDURE
1. Press and hold ON button until colorimeter turns on.
2. Press ENTER to start.
3. Press ENTER to select TESTING MENU.
4. Select ALL TESTS (or another sequence containing 78 Phosphate L)
from TESTING MENU.
5. Scroll to and select 78 Phosphate L from menu.
6. Use the 1 mL pipet (0354) to add 1 mL of the soil extract to a clean tube
(0290) and dilute to the 10 mL line with deionized water.
7. Insert tube into chamber, close lid and select SCAN BLANK.
8. Remove tube from colorimeter. Use 1.0 mL pipet (0354) to add 1.0 mL of
*Phosphate Acid Reagent (V-6282). Cap and mix.
9. Use the 0.1 g spoon (0699) to add one measure of *Phosphate Reducing
Reagent (V-6283). Cap and shake until powder dissolves. Wait 5 minutes
for full color development. Solution will turn blue if phosphorus is present.
10. At end of 5 minute waiting period, mix, insert tube into chamber, close lid
and select SCAN SAMPLE. Multiply the result by 32 to determine the
phosphorus concentration in lb/acre.
11. Press OFF button to turn colorimeter off or press EXIT button to exit to a
previous menu or make another menu selection.
PHOSPHORUS IN ALKALINE SOILS
A special extraction procedure is used for determining the available
phosphorus content of Western U.S. alkaline soils where the pH value is above
7.0.
EXTRACTION PROCEDURE
1. Use the 1 mL pipet (0354) to add 1 mL of the *Special NF Extracting
Solution (6362) to the test tube (0701) then add deionized water to the
graduation.
2. Add 3 one gram measures of soil using the 1 g spoon (0697) to the
extracting solution in the vial.
3. Cap the vial and shake for a period of 5 minutes.
4. Filter using the funnel (0459) and filter paper (0463). Collect all of the
filtrate.
5. Perform the Phosphorus test according to the Phosphorus procedure given
above.
74 SMART2 SOIL MANUAL 1.07