Splendor of Sustainable Agriculture: Effects of Salt on Soil Sedimentation- Soil Structure/Texture

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 by Peter Emau

For a farmer dedicated to sustainable agriculture, one question to ask is what effects the massive amounts of salt (applied on the roads and driveways to melt snow ice in Winter) has on natural soil structure or texture.  As the snow melts, salt is carried away into nearby land where it may affect soil structure.  Soil texture affects growth of plant roots and growth soil microbes- both of which are the basis or healthy gardening and pasture for animals.

Therefore, I tested the effects using simple soil sedimentation test.  Basically, get soil from up to 20 cm depth in the pasture, add it to jars up to a third of the jar, then add different amounts of salt.  Jar #2 has no salt.  Jar #4 has a quarter teaspoon of salt.  Jar #6 has half teaspoon of salt. Add water to all jars bring total volume to 500 milliters and shake to create a soil suspension so that soil is approximately 25%(v/v). Assuming 1 teaspoon is 5.7grams of salt,  the final concentration of salt in jar #4 is 2.8 mg/milliters.  Jar # 6 has 5.7 mg/milliters. 

Then, let the jars sit for 3 days and check sedimentation as shown in pictures below:

Jar No 2 has no salt; Jar  No 4 has 2.8 mg/mL salt


Jar #2 has no salt; Jar # 4 has 2.8 mg/mL salt; Jar # 6 has 5.7 mg/mL salt


The results are clear. Without salt, sedimentation test shows clearly the sand, silt and clay layers since these particles sedimentation at different rates due to their differences in size, weight and electrical charges, which is neutralized by as little as 2.8 mg/milliters concentration of salt used on driveways or roads to melt ice. Similar effects are produced by table salt. The salt appears to exert its effect by neutralizing the differences in the rate of sedimentation of clay and silt.



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