The soluble salts test should be requested if:
- "black dirt" has been hauled in and poor growth is observed
- there is possible damage from salt used on streets and sidewalks or excess application of fertilizer
- the grass looks burned even when adequate water is present
- the soil is poorly drained and located in the south central or western part of Minnesota
- for golf greens - since golf greens must be heavily fertilized - the salt content should be monitored and taken into consideration when making fertilizer recommendations
Soil samples are evaluated for salinity by first determining the electrical conductivity (E.C.) of a 1:1 suspension. Two 10 gram scoops are mixed with 20 milliliters deionized water to form a slurry, which is stirred intermittently for 30 minutes. The E.C. is determined by the Orion Star A212 conductivity meter, and is reported in units of millimhos per centimeter (mmohs/cm).
Slightly to strongly saline soils (conductivity more than 0.9 millimhos) are subjected to a more precise test. A saturated soil paste is prepared by slowly adding deionized water to about 50 cubic centimeters of soil until the mixture is a thick paste. After an equilibration time of two hours, the saturation paste is filtered under suction. The electrical conductivity is determined on the filtrate with the Orion Star A212 conductivity meter, and is reported as mmohs/cm.