LaMotte DCL-20 Colorimeter - Manual (Page 9)

SOLUBLE SALTS (TOTAL DISSOLVED SALTS)
PROCEDURE
1. Fill a 50 mL beaker (0944) with the soil to be tested, tapping it lightly to eliminate any trapped air and then strike off
the surface.
2. Empty the contents of the beaker into the 300 mL bottle (0991) and add 100 mL of deionized water.
3. Cap the bottle and shake vigorously. Allow to stand for thirty minutes. During the thirty minute waiting period the
bottle should be shaken vigorously three or four times.
4. Filter the contents of the bottle using funnel (0459) and filter paper (0463) and collect the filtrate in a 100 mL bottle
(0990) which is then used as a conductivity chamber.
5. Take conductivity reading according to method given for General Operating Procedure.
6. To convert conductivity to Soluble Salts (Total Dissolved Salts), use the following formula.
Micromhos/cm @ 25°C x 0.7 = ppm of sol u ble salts (to tal dis solved salts)
SOLUBLE SALTS
Below 1000 parts per million most plants will get along well. However, green-house and many sensitive garden plants may
be damaged if the soluble salts are over 500 parts per million of chlorides, particularly some of the most sensitive legumes. If
the soluble salts are greater that 1000 parts per million, the chlorides and sulfates should be determined to learn whether
the soluble salts are chlorides or sulfates. In calcareous soils, the sulfates represent gypsum and have little effect on the
production of plants.
9
1985-01 • 10/01