LaMotte SMART 2 Electronic Soil Lab - Manual (Page 50)

SOLUBLE SALTS
(TOTAL DISSOLVED SALTS)
Most plants will get along well at soluble salts concentrations of below 1000
parts per million. However, greenhouse 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.
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). 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. Determine the TDS reading of the sample by following the instructions for
the TDS 5 Meter.
6. To convert conductivity to Soluble Salts (Total Dissolved Solids), use the
following formula.
ppm Soluble Solids (Total Dissolved Solids) =
Micromhos/cm @ 25
°C x 0.7
50 SMART2 SOIL MANUAL 1.07