Testing for Salinity in Soils
Sampling Protocol to Assess Possible Saline Soil Conditions
“Field Screening”
The following procedure should be used for testing soils when a ‘salt’ problem is suspected. To nsure accurate interpretation, it is important that the sampling procedure be followed. A sample submittal form has been prepared for use with this “field screening” endeavor. A form should be completed as accurately as possible for each site sampled.
The sampling protocol is as follows:
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A site that is suspected of having a ‘salt’ problem is selected and identified with GPS coordinates.
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The sample submittal form is completed with the following information:
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a. Sampling site identification
b. GPS coordinates, Latitude and Longitude- decimal degree format
c. Date of sampling
d. Name of the person taking the sample
e. Address, telephone number and email address of the person
sampling
f. Sampling depths ( 0-3, 3-6 and 6 -12 inches), as appropriate, refer to
#6
g. Record E C meter reading, refer to #6
h. Descriptive name of the sampling site
i. Estimated or known depth of the flood waters received at the site
j. Days since flood waters have fully drained
k. Previous crop or Next crop
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Create a composite sample of eight cores (from the 0 – 3 inch depth) within a six foot diameter of the site; placing the cores into a clean, dry plastic container. Mix the composite sample thoroughly. If the soil is sticky or clod, cut or break the soil cores into one-quarter inch sized pieces before mixing.
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Place approximately one-fourth cup of the mixed sample into a plastic jar (with a lid). Place an equal volume of distilled water into the container. Put the lid on the jar and shake it vigorously until the soil aggregate is completely dispersed.
- Open the jar. Remove the protective cap on the bottom portion of the E C meter. Turn the meter on and insert the meter electrodes into the soil-water mixture. Do not immerse the meter electrodes above the immersion indicator level.
- Take the reading while the soil particles are still suspended in solution. Allow the reading to stabilize (reading remains about the same for about 10 seconds). Record the reading and the units of measure on the “Field Screening” form. Turn the meter off. Thoroughly rinse the lower portion of the meter and the two electrodes with distilled water and replace the protective cap on the meter. If the E C reading of the 0 - 3 inch sample is lower than 1.5 dS/m there is no ‘salt’ problem at this site.
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If the E C value is greater than 1.5 dS/m, appreciable ‘salt’ accumulation may have occurred at the site. For further testing, collect the 0 - 3 inch sample and go back into the same sampling locations (holes) for 3 -6 inch and 6 – 12 inch samples. As with the 0-3 inch sampling, collect composite samples, place them into plastic bags and use a waterproof marker to identify them by site location and sampling depth.
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Samples collected for this “Field Screening” with the appropriate completed form, and a check ($5.00 for each sample collected) can be delivered to your local LSU AgCenter Extension Office or mailed directly to the LSU AgCenter Soil Testing and Plant Analysis Laboratory at the address below. Results should be available within four days after the laboratory receives the sample.
Soil Testing Plant Analysis Laboratory
104 Sturgis Hall
LSU AgCenter
Baton Rouge, LA 70803- 2110
Please address questions on field screening for salinity in soils to:
Mr. J. Chester Stevens, Soil Specialist
Louisiana Cooperative Extension Service
Phone: 318-427-4424
Cell: 318-308-0754
Email: jstevens@agcenter.lsu.edu