COIROLOGY JOURNAL · Substrate chemistry
Coir chemistry: salts, buffering and CEC
Coir has both a physical structure and chemical behaviour. Understanding the difference between dissolved salts and exchangeable ions makes product specifications more useful.
What the husk contributes
Horticultural coir comes from the coconut husk. It contains structural plant material, including cellulose and lignin, alongside mineral constituents. The source and processing affect the finished material.
Avoid treating a single chemical composition table as a universal specification. Ask for results relevant to the actual product and intended application.
Dissolved salts and EC
Electrical conductivity, or EC, indicates the combined electrical contribution of dissolved ions in the measured solution. It cannot identify how much of an individual nutrient or unwanted ion is present.
A result also depends on sample preparation and extraction. Record the method, units and sample reference rather than comparing isolated numbers from different reports.
Washing and buffering do different jobs
Washing can remove soluble salts when they dissolve and the water drains away. Adding water without removing it mainly dilutes the solution; it does not make the total salt content disappear.
Coir also has negatively charged exchange sites that retain cations. Buffering with a suitable calcium-containing treatment changes their occupancy, exchanging some potassium and sodium for calcium. The released ions still need to be managed through the process.
Chloride is an anion, so it should not be described as a cation displaced by calcium from these sites. It is relevant to the soluble-salt part of the picture.
CEC is not a complete feeding programme
Cation exchange capacity describes a capacity to retain exchangeable positive ions. It is not the same as the quantity of all nutrients available to a plant, and it does not prevent all leaching.
ISHS research on coir highlights why exchangeable cations matter to processing and fertilisation. For a purchase, ask which treatment and analytical checks apply rather than relying on the word buffered alone.
Turn chemistry into a useful specification
Separate questions about pH, soluble salts, particular ions and processing. Decide which analysis answers the issue you actually have.
Explore the conceptual models on Substrate Science, or discuss a sample with SubstrateLab. Laboratory findings still need interpretation in the crop and irrigation context.
Sources & further reading
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