LaMotte SMART 3 Electronic Soil Lab - Manual (Page 82)

82 SMART3 Soil 1.11
PROCEDURE
Press and hold 1. until colorimeter turns on.
Press 2. ENTER to select TESTING MENU.
Select 3. ALL TESTS (or another sequence containing 083 Potassium) from
TESTING MENU.
Scroll to and select
4. 083 Potassium from menu.
Use the 1 mL pipet (0354) to add 2 ml of the soil extract to a clean tube 5.
(0290) and dilute to the 10 mL line with deionized water.
Insert tube into chamber, close lid and select SCAN BLANK.
6.
Remove tube from colorimeter. Add 4 drops of *Sodium Hydroxide, 1.0N 7.
(4004WT). Cap and mix.
Use the 0.05 g spoon (0696) to add one measure of *Tetraphenylboron
8.
Powder (6364). Cap and shake vigorously until all of the powder has
dissolved. Wait 5 minutes.
At end of 5 minute waiting period, mix tube again to suspend any settled
9.
precipitate. Insert tube into chamber, close lid and select SCAN SAMPLE.
Multiply the result by 50 to determine the potassium concentration in lb/acre.
Press
10. to turn the colorimeter off or press
EXIT
to exit to a previous
menu or make another menu selection.
NOTES:
For best possible results, a reagent blank should be determined to account
for any contribution to the test result by the reagent system. To determine the
reagent blank, follow the above test procedure to scan a distilled or deionized
water blank. Then follow the above procedure to perform the test on a distilled
or deionized water sample. This test result is the reagent blank. Subtract
the reagent blank from all subsequent test results of unknown samples. It
is necessary to determine the reagent blank only when a new lot number of
reagents are obtained.
For the most accurate results, the sample and reagents should be at 25±4°C.
POTASSIUM CONCENTRATION CHART
POUNDS PER ACRE RANGE
0-44 lb/acre Very Low
50-76 lb/acre Low
82-143 lb/acre Medium
144-281 lb/acre High
Over 294 lb/acre Very High
Test P
rocedures