Home › News › Specification

Cocopeat EC and pH: Preparing Substrate for Horticulture Buyers

Cocopeat is sold on two numbers. Both are achievable, both cost money to achieve, and one of them is routinely confused with a completely different process.

Cocopeat — coir pith — is the fine material left when fibre is separated from coconut husk. As a growing substrate it holds water well, drains well and resists compaction. It also arrives, untreated, carrying salt.

What EC measures, and why growers care

Electrical conductivity measures dissolved salts. In coir the salts of concern are mainly potassium and sodium — naturally present in the husk, and increased where husks have been retted in brackish or sea water, or simply stored near the coast.

Raw, untreated coir pith commonly sits somewhere around 2 to 6 mS/cm. That is high enough to injure seedlings and to disrupt a carefully planned fertigation programme in a professional greenhouse. A grower dosing nutrient precisely does not want an unknown quantity of potassium arriving free with the substrate.

European growers typically ask for EC below 0.5 mS/cm in a 1:1.5 water extract; some propagation specialists ask for lower. Note the method — EC figures are meaningless without it, because a 1:5 extract and a 1:1.5 extract on the same material give different numbers. A supplier quoting EC without naming the extraction ratio is quoting nothing.

Washing and buffering are not the same thing

This distinction is worth more than any other paragraph on this page, and it is where most confusion lives.

Washing

Washing means flushing the pith with fresh water to carry away soluble salts. It lowers EC. It requires a lot of clean water, and time for the material to drain and dry back to a packable moisture level.

Buffering

Buffering is chemistry, not rinsing. Coir has cation exchange capacity — sites that hold positively charged ions. Sodium and potassium occupy those sites, and washing alone does not remove them, because they are held rather than dissolved. Treating the pith with a calcium solution — calcium nitrate is common — displaces the sodium and potassium from those sites so they can then be rinsed out.

Why it matters to a grower: unbuffered coir can test at a comfortable EC on delivery and then release sodium and potassium later, when calcium and magnesium from the grower's own feed displace them. The substrate passed the incoming test and still disrupted the crop.

If your crop is sensitive, ask for buffered — not merely washed low-EC. They are different products at different prices, and some suppliers use the words interchangeably.

pH, and the other specifications

Coir sits naturally in a reasonable range for most crops, typically around pH 5.5 to 6.8. It is rarely the problem EC is, but it belongs on the specification.

Parameter	Typical requirement	Note
EC	≤ 0.5 mS/cm	State the extraction ratio, e.g. 1:1.5
pH	5.5–6.8	Same extract
Moisture	≤ 15%	Higher risks mould in a sealed container
Compression	5:1 typical	Determines blocks per container
Sand / silt	Low, stated	The contaminant most often ignored
Fibre content	As agreed	Affects air porosity

The honest cost of low EC

Low EC is not a quality a supplier either has or lacks. It is bought with fresh water, tank space and time — sometimes weeks of soaking, draining and re-drying before the material can be pressed into blocks.

Which is why a quotation offering EC below 0.5 at the same price as untreated pith deserves a second look. Either the process happened and the price does not reflect it, or the process did not happen and the number came from somewhere else.

What to ask

• Washed, or washed and buffered? If they treat these as synonyms, keep asking.
• EC at what extraction ratio, by what method?
• Was fresh water used? Washing coir in brackish water is not washing.
• Sand content? Cheap pith is often cheap because of what came with it.
• Batch certificate, or a typical value?

What we do

We produce cocopeat blocks at our site in Baubau, currently 21 tonnes a month, screened to remove long fibre and sand. Low EC is available on request — and we will quote it as what it is: a process that costs water and time, not a line on a specification sheet. Samples are free, and they ship with the batch certificate so you can test against your own lab.