The short answer: all coco peat starts out salty. Washing rinses the loose salts out with water and brings EC down. Buffering goes one step further: coir is soaked in a calcium solution (usually calcium nitrate) so that calcium takes the place of the potassium and sodium held on the fibre. Well-washed, low-EC coco peat is enough for many uses, especially blending, propagation and organic growing. Buffered coir is mainly chosen for salt-sensitive, fertigated crops in slabs and grow bags. Whichever you buy, the number that matters is EC measured by a stated method. Without the method, an EC figure on a datasheet cannot be compared with another supplier's.
Key facts
- Raw coir EC: "3–6 mS/cm" has been seen, and "6 mS/cm or higher" in a 1:1.5 extract (Hort Americas; Klasmann-Deilmann).
- Washed coir: "< 1 mS/cm" (Klasmann-Deilmann); a commercial washed grade is specified at "<0.7", a buffered grade at "<0.5" (Profile Products).
- "If coir is washed well and its EC is below 0.5 mS/cm or lower, then the coir shouldn't have to be buffered for most crops" (Dr Hugh Poole, via Hort Americas).
- Calcium-nitrate-buffered coir "is not able to be used in organic crop production" (Profile Products).
Unwashed, washed and buffered coco peat compared
Coco peat (also called cocopeat, coir pith or coco coir) is the fine, spongy material left when the long fibre is separated from the coconut husk. Straight from the husk it is too salty for most crops. Suppliers sell it in three broad conditions:
| Unwashed (raw) | Washed | Buffered | |
|---|---|---|---|
| What was done | Nothing; sometimes only sieved | Rinsed repeatedly with fresh water | Washed, then soaked in a calcium (often calcium + magnesium) solution and rinsed again |
| Typical EC | Up to 6 mS/cm or higher (1:1.5) | Below 1 mS/cm; good grades below 0.5–0.7 | Below 0.5 mS/cm (1:1.5) |
| Sodium (Na) | 200–1000 ppm | 30–50 ppm (washed + buffered) | 30–50 ppm (washed + buffered) |
| Potassium (K) | 1500–7000 ppm | 100–500 ppm (washed + buffered) | 100–500 ppm (washed + buffered) |
| pH | 5.5–6.5 | 5.5–6.8 | 5.5–6.5 |
| Organic production | Not suitable as is | Suitable (check with your certifier) | Not when buffered with calcium nitrate |
| Typical use | Further processing only | Blending, potting mixes, propagation, organic growing, many grow-bag crops | Salt-sensitive fertigated crops in slabs and bags |
Sources: EC ranges from Klasmann-Deilmann (1:1.5 extract) and Profile Products technical data sheets; Na, K and pH from HORIBA, which reports raw coir against a combined "washed and buffered" column, so it does not separate the two. Ranges vary with the raw material and the test method.
Why raw coir needs treatment
Coir naturally contains salts, and how much varies a lot with origin and handling. Published surveys of coir from different countries show how much it varies: one study of 12 coir dust sources reported EC from 0.3 to 2.9 mS/cm, potassium from 19 to 948 mg/L and chloride from 26 to 1636 mg/L (Evans, Konduru & Stamps, HortScience, 1996). Another study of 13 coir dusts from Asia, America and Africa found salinity from 0.39 to 5.97 mS/cm (Abad et al., Bioresource Technology, 2002).
The salt sits in two places:
- Loose (soluble) salts in the water held by the pith, mostly sodium, potassium and chloride. These raise EC and are what washing removes.
- Ions held on the exchange sites of the fibre. Coir has a cation exchange capacity: it holds positively charged nutrients on its surface. Straight from the husk, those sites are mostly occupied by potassium and sodium.
What goes wrong with unbuffered coir
When you feed a crop growing in coir whose exchange sites are loaded with potassium and sodium, the coir swaps some of them for the calcium and magnesium in your nutrient solution. The plant sees less calcium and magnesium than you are feeding. Dr Hugh Poole described a grower feeding 50 ppm calcium whose leachate "may only contain 10 ppm calcium" (Hort Americas). This is why some growers see calcium or magnesium deficiency early in the crop and why "Cal-Mag" advice is common with coco.
Whether this matters depends on how much potassium and sodium is left after washing, on your crop and on your feed.
How washing works, and where it stops
Washing means soaking and rinsing the pith with fresh water, often in several cycles, then draining and drying it before it is compressed into blocks, briquettes or bags. It removes the loose salts and is the main way EC is brought down.
Two things limit what washing can do:
- The water. Washing with water that is itself salty or hard leaves salts behind. When you compare suppliers, a low EC result matters more than the number of washes claimed.
- The exchange sites. Water alone removes loose salts much more easily than the potassium and sodium held on the fibre. That is why Klasmann-Deilmann classes washed coir as "< 1 mS/cm" but treats buffered coir as a separate grade.
A buffering trial from the University of Peradeniya, Sri Lanka, illustrates this. Water-only treatment left available sodium and potassium at 138 and 287 mg/L, while the best buffer tested brought them down to 71 and 91 mg/L (Ranaweera et al., 2015).
At CVM Fiber and Industries, coco peat is washed with water to reduce EC. No calcium nitrate or other chemicals are used. If your crop needs buffered coir, read the next two sections before you decide, and talk to your agronomist about the calcium and magnesium in your feed.
How buffering works
Buffering saturates the coir's exchange sites with calcium (and often magnesium) so they no longer pull these nutrients out of your feed. In practice:
- The coir is washed first.
- It is soaked in a calcium solution. Calcium nitrate is the most common; Klasmann-Deilmann's technical note shows calcium nitrate and magnesium sulphate.
- Calcium displaces potassium and sodium from the exchange sites.
- The coir is rinsed again to wash out the released potassium and sodium, then tested.
Published rates and soaking times differ widely between suppliers and patents, so treat any single "recipe" with care. What a buyer should ask for is the result: EC, and if possible sodium and potassium on the certificate of analysis.
What buffering does not do
- It does not make coir a fertiliser. Buffered coir still needs a complete feed.
- It does not fix poorly washed coir. Buffering only works on coir that has already been washed.
- It is not always better. Growing-media blenders often prefer washed, unbuffered coir so they can set the chemistry of their mix themselves.
Buffered coir and organic growing
Two independent sources say calcium-nitrate buffering rules coir out of organic production:
- "Buffering is not an option for organic growers" (Dr Hugh Poole, via Hort Americas).
- Profile Products' buffered grade is "treated with calcium nitrate… This product is not able to be used in organic crop production" (technical data sheet).
Organic growers therefore usually specify well-washed, low-EC coir with no chemical treatment and manage calcium and magnesium through permitted inputs. Whether a particular growing medium is accepted is decided by your organic certification body, so send them the supplier's composition and treatment statement before you order.
EC grades and test methods
Common EC bands
Many sellers use three bands for coco peat blocks, for example "<0.5"* for low EC and *">0.8" for high EC (The Coco Depot):
| Band | EC (mS/cm) | Typical use |
|---|---|---|
| Low EC | below 0.5 | Propagation, seedlings, salt-sensitive crops, grow bags |
| Medium EC | 0.5–0.8 | Potting mixes, blending, less sensitive crops |
| High EC | above 0.8 | Mulch, landscaping, further washing |
These bands only mean something if the test method is stated.
Why two labs give two different numbers
EC is measured on a water extract of the coir, and the amount of water used changes the reading:
- 1:1.5 by volume. Common in coir and greenhouse horticulture. CANNA's procedure, for example, uses 150 ml demineralised water topped up with coco to 250 ml, left to settle for at least two hours, then measured (CANNA).
- 1:5 by volume. The European standard method for growing media, EN 13038. pH is measured by EN 13037.
- Saturated media extract (SME), 1:2 and pour-through are also used.
The same sample reads lower at 1:5 than at 1:1.5, simply because the salts are more diluted. There is no published conversion factor for coir between the two, so don't convert. Ask for the method instead. Also note that EC targets quoted for growing crops (fed substrate, for example CANNA's 1.1–1.3 at 1:1.5) are not raw-material specifications. Don't mix the two.
Which treatment for which crop and system
This table is general guidance. Your crop, water quality and feed decide the final choice.
| Crop or system | Usually specified | Why |
|---|---|---|
| Tomatoes, cucumbers, peppers in slabs or grow bags | Low-EC; buffered by many growers | Fertigated, salt-sensitive start; buffering avoids early Ca/Mg drawdown |
| Strawberries and soft fruit in grow bags | Low-EC; buffered or washed with an adjusted feed | Sensitive to sodium; long season |
| Propagation, seedlings, plugs | Lowest EC available (below 0.5) | Young roots are the most salt-sensitive |
| Potting mixes and nursery blending | Washed, low or medium EC, unbuffered | The blender sets the chemistry of the mix |
| Organic production | Washed, low-EC, no chemical treatment | Calcium-nitrate buffering is not permitted |
| Mulch, landscaping, erosion control | Medium or high EC | Salt matters less |
Does the treatment change the format?
Treatment and format are separate choices. The same washed coco peat can be supplied as:
- 5 kg coco peat blocks: compressed blocks for bulk shipping; you hydrate and expand them on site. Ask the supplier for the expansion in litres and how it was measured, because published figures for a 5 kg block range widely.
- 650 g briquettes: small bricks for propagation and retail.
- Grow bags and open-top slabs: pre-filled for greenhouse crops.
- Coconut husk chips: coarser, airier pieces of husk; washing matters just as much here.
What to put in your purchase specification
A clear spec avoids disputes when the container arrives. A template you can copy:
| Parameter | What to ask for |
|---|---|
| Treatment | Washed / buffered, and the buffering agent if any (or "no chemical treatment") |
| EC | Maximum value and the method (e.g. "EC ≤ 0.5 mS/cm, 1:1.5 v/v") |
| pH | Range and method (e.g. EN 13037) |
| Sodium and potassium | Maximum values and the extraction used, if your crop is sensitive |
| Moisture | Maximum % at dispatch |
| Sand and foreign matter | Maximum % |
| Expansion | Litres per block and how it is measured |
| Particle grade | Fine pith, or pith with fibre or chips, and any ratio |
| Documents | Certificate of analysis per lot; export documents your country requires |
| Sampling | Pre-shipment samples or retained samples per lot |
Where the published numbers disagree
Be wary of any guide, including this one, that presents a single "correct" number:
- EC cut-offs differ: below 0.5, below 0.7 and below 1 mS/cm are all used for "washed" or "low EC", often without a method.
- pH for coir is quoted anywhere from about 5.5 to 7.
- Block expansion claims for a 5 kg block vary a lot between listings.
- Buffering rates (kilograms of calcium nitrate per cubic metre, soaking hours) vary from source to source.
The way through is the same every time: agree the parameter, the limit and the test method with your supplier, and check the certificate for each lot.
FAQ
What is the difference between washed and buffered coco peat?
Washed coco peat has been rinsed with fresh water to remove loose salts and lower EC. Buffered coco peat has also been soaked in a calcium solution, usually calcium nitrate, so that calcium replaces the potassium and sodium held on the fibre. Buffering is an extra step after washing, not a replacement for it.
Does coco peat need to be buffered?
Not always. If coir is washed well and its EC is below about 0.5 mS/cm, many crops grow well in it without buffering, provided the feed supplies enough calcium and magnesium. Buffering is mainly chosen for salt-sensitive, fertigated crops in slabs and grow bags. Blenders and organic growers usually prefer washed, unbuffered coir.
What EC should low EC coco peat have, and how is it measured?
Low EC coco peat is commonly sold as below 0.5 mS/cm. The figure depends on the test method: a 1:1.5 volume extract is common in horticulture, while the European standard EN 13038 uses a 1:5 extract, which gives a lower reading for the same sample. Always ask which method was used.
Why does unbuffered coco coir cause calcium and magnesium deficiency?
Raw coir holds potassium and sodium on its exchange sites. When you feed it, the coir takes up calcium and magnesium from the nutrient solution in exchange, so less reaches the plant. In one reported case a feed with 50 ppm calcium gave only about 10 ppm calcium in the leachate. Raising calcium and magnesium in the feed, or using buffered coir, avoids this.
How is coco peat buffered commercially?
The coir is washed, soaked in a calcium solution (most often calcium nitrate, sometimes with magnesium sulphate), rinsed again to remove the displaced potassium and sodium, then dried and tested. Rates and soaking times differ between suppliers, so judge the result on the certificate of analysis rather than the recipe.
Can buffered coco coir be used in certified organic growing?
Coir buffered with calcium nitrate is generally not accepted in organic production. Organic growers usually specify washed, low-EC coir with no chemical treatment. Your organic certification body makes the final decision, so share the supplier's treatment statement with them before ordering.
Is CVM coco peat buffered?
No. CVM Fiber and Industries washes its coco peat with water to reduce EC and does not use calcium nitrate or other chemicals. If your crop needs a calcium and magnesium adjustment, make it in your feed as your agronomist advises.
How can I check whether a delivery matches my spec?
Ask for a certificate of analysis for each lot that states EC, pH and the test methods, plus sodium and potassium if your crop is sensitive. On arrival, run your own EC and pH test with the same method on a sample from several blocks or bags. If the method matches, the numbers should be comparable.
Sources
- Hort Americas / Dr Hugh Poole: Buffering coir not necessary if it's processed properly
- Klasmann-Deilmann: Coir chemically (technical note)
- Profile Products: Coir Grade A Washed and Coir Buffered technical data sheets
- HORIBA: Rapid pH and nutrient analysis of coco coir and coco peat
- Ranaweera, Dharmakeerthi & Gunasena (2015), University of Peradeniya: buffering trial abstract
- Evans, Konduru & Stamps (1996), HortScience 31(6): 965–967: abstract
- Abad et al. (2002), Bioresource Technology 82: 241–245: abstract
- CANNA: Measuring coco: the extraction method
- The Coco Depot: Low EC and high EC coco peat
Comparing coir with peat moss? See our coco coir vs peat comparison. Ready to order or want a sample of our washed, low-EC coco peat? Contact our export team.