01 · Direct answer.
It depends on the crop's salt tolerance. In Carve's line, Natural coir pith measures 0.8 to 1.5 mS/cm (1:5 extract) and suits coffee, clonal eucalyptus, citrus, landscaping and leafy vegetables. Washed is below 0.7 mS/cm and suits potted ornamentals, forestry seedlings and soilless vegetables. Buffered is below 0.5 mS/cm and is the grade for strawberry, tomato, flowers, orchids, seed sowing and organic production.[4] EC is measured on every lot and the limit goes into the contract.
| Grade | EC (1:5) | Suited crops |
|---|---|---|
| Natural (unwashed) | 0.8-1.5 mS/cm | Coffee, clonal eucalyptus, citrus, landscaping, leafy vegetables |
| Washed | < 0.7 mS/cm | Potted ornamentals, forestry seedlings, soilless vegetables |
| Buffered | < 0.5 mS/cm | Strawberry, tomato, flowers, orchids, seed sowing, organics |
Bands as published on Carve's Coir Pith data sheet and Import Coir from Brazil. All three grades are available; EC is measured per lot and the grade is defined in the contract with the buyer.
02 · Why coconut husk EC varies.
Raw dry coconut husk has a documented EC of 0.4 to 6.0 mS/cm (1:5) in the EMBRAPA literature, a fifteen-fold range within the same material.[1] The salts are part of the husk itself, not external contamination:
- Potassium 1.60 %, chlorine 1.80 % and sodium 0.38 % in dry husk, according to EMBRAPA's Table 1.[1]
- The pH of raw dry husk runs 4.9 to 6.0.[1]
- The washing target cited by EMBRAPA is EC below 1.0 mS/cm.[1]
This is why no serious data sheet publishes a single EC value for raw pith: what can be published is the band of each grade and a measurement on each lot.
Where the husk comes from sets the starting point. Carve's raw material is dry mature husk, rain-aged inland and never retted in brackish water; washing uses low-conductivity well water, and EC is measured on every lot.[6] Most coir traded internationally is made from husk retted in brackish coastal lagoons, and research on Indian and Sri Lankan coir found coefficients of variation in EC of 39 % to 165 % between batches.[6] The origin comparison is covered in Brazilian coir vs Asian coir.
03 · Which crops are salt-sensitive.
Adalberto Romero, with more than 20 years in the coir substrate industry, lists lettuce, strawberry and blueberry among the salt-sensitive crops, and explains the mechanism that separates washed from buffered pith:[2]
- Water alone does not displace the sodium and potassium held in coir's organic complex. Only calcium or magnesium does.[2]
- In a sensitive crop grown on pith that was only washed, fertigation with calcium and magnesium performs that displacement inside the crop, and the released sodium and potassium reach the roots.[2]
- The calcium or magnesium treatment uses one of the two, not both, and a final wash removes the excess.[2]
- This is why strawberry, tomato, flowers, orchids and seed sowing are matched to Buffered in Carve's table, not only to Washed.[4]
David Cadena, a Mexican coir substrate specialist, adds that coir gives the grower a management buffer for EC and pH that synthetic substrates do not, and that when a nursery crop later moves to production in coir, coir in both phases is ideal.[3] The detail of each process is in Washed vs unwashed coir pith.
04 · How EC is measured and reported.
- Method: 1:5 extraction by volume, calibrated conductivity meter, on every lot.[4]
- The extract ratio changes the reading: a 1:1.5 extraction gives different values from a 1:5 extraction. Compare data sheets only when the ratio is the same.[5]
- The result is printed on the label and opened by the QR code on each bag, together with pH, moisture, bulk density and particle size.[4]
- A lot outside the contracted limit does not ship.[4]
What appears on the lot report and how to check each number is in Coir pith lot report (COA).
05 · How to fix EC in the contract.
- State the crop and the phase (sowing, seedling, production). The table in section 01 points to the grade.
- Choose the grade by process (Natural, Washed or Buffered), not by an isolated number.
- Write an EC ceiling (1:5) into the contract. Substrate manufacturers often set a ceiling and correct EC in their final blend.[4]
- Ask for the lot report before the container is stuffed and check the QR on arrival.
Company registration and location data are on Company facts; the full purchase checklist (moisture basis, expansion, packing, HS code, transit) is in the specification checklist.
06 · Frequently asked questions.
Can Natural coir pith be used for strawberries?
Not as the standard recommendation: for strawberry Carve recommends Buffered coir pith, with EC below 0.5 mS/cm (1:5). Strawberry is among the salt-sensitive crops cited by Adalberto Romero, and in those crops pith that was only washed carries a risk: when the grower fertigates with calcium and magnesium, those ions displace the sodium and potassium held in coir's organic structure, which return to the root zone.
What EC does coir pith need for tomatoes?
In Carve's line the grade for tomato is Buffered, with EC below 0.5 mS/cm (1:5), the same grade recommended for strawberry, flowers, orchids, seed sowing and organic production. Soilless vegetables in general use Washed, below 0.7 mS/cm. The exact limit is fixed in the contract and checked on the report of each lot.
What EC does coir pith need for seedlings and nurseries?
Forestry seedlings and potted ornamentals use Washed, with EC below 0.7 mS/cm (1:5). Clonal eucalyptus, coffee and citrus are among the crops suited to Natural, 0.8 to 1.5 mS/cm, with a limit in the contract. Seed sowing of sensitive crops uses Buffered, below 0.5 mS/cm.
Are EC 1:5 and EC 1:1.5 the same thing?
No. The substrate-to-water ratio of the extract changes the number read on the conductivity meter, and a 1:1.5 ratio gives different values from a 1:5 ratio. All bands on this page and Carve's lot report use the 1:5 extract by volume. When comparing data sheets from different suppliers, check the ratio before comparing the numbers.
Why does Carve not publish a single EC value for its coir pith?
Because raw dry coconut husk has a documented EC of 0.4 to 6.0 mS/cm (1:5) in the EMBRAPA literature, a fifteen-fold range that comes from the husk's own natural salts (potassium 1.60 %, chlorine 1.80 %, sodium 0.38 %). A single value would not describe the material. Carve publishes the band of each grade, measures every lot and fixes the limit in the contract.
07 · Sources.
- EMBRAPA Tabuleiros Costeiros, Comunicado Técnico 226 (COT-226-19): raw dry husk EC 0.4-6.0 mS/cm, pH 4.9-6.0, washing target below 1.0 mS/cm, composition K 1.60 % / Cl 1.80 % / Na 0.38 % of dry husk.
- Ing. Adalberto Romero webinar (Science Fetti / El Semillero, Colombia, 2025): salt-sensitive crops, water does not displace Na/K from the organic complex, calcium or magnesium treatment, risk of washed-only pith in sensitive crops.
- Lic. David Cadena webinar (Mexico, hosted by Riego Rotoplas, 2026): coir as an EC and pH management buffer, coir-to-coir recommendation between nursery and production.
- Carve public specification: Coir Pith and Quality pages: bands by grade, 1:5 method, measurement per lot, QR on every bag.
- Carve bench procedure: the extract ratio is stated on every result, because 1:1.5 and 1:5 give different readings.
- Carve raw-material description on Import Coir from Brazil (dry inland husk, never retted, artesian well water for washing); Prasad, M. (1997), Acta Horticulturae 450 (EC variation in Indian and Sri Lankan coir); Raviv, M., Lieth, J.H. & Bar-Tal, A. (2019), Soilless Culture, 2nd ed., ch. 8.