Two numbers on a coco peat specification sheet decide more about how a crop starts than any other: EC and pH. Both describe the water that sits in the growing media, the water the roots actually drink. This guide explains what each number measures, why propagation growers ask for Low EC blocks, and how to check a delivery yourself.
What EC measures
EC, or electrical conductivity, tells you how much dissolved salt is in the media’s moisture. Pure water barely conducts electricity; add salts and the reading rises. Specification sheets usually give it in millisiemens per centimetre (mS/cm), which is the same value as decisiemens per metre (dS/m).
Coconut husk carries soluble salts naturally, mainly potassium, sodium and chloride. Left in the pith, those salts reach the roots before any fertiliser does, so the EC of the media is the starting point for every feed you plan.
Why Low EC matters for young roots
Seedlings, cuttings and young plugs are the most sensitive stage of a crop. High salt levels around fresh roots make it harder for them to take up water, which can slow germination and rooting or scorch tender tips. That is why nurseries, greenhouse propagators and hydroponic growers usually ask for Low EC media: they want to control exactly what the roots receive, through their own nutrient solution.
Established plants in open ground are more forgiving. When coco peat is mixed into soil for conditioning, landscaping or bed preparation, irrigation and rain carry much of the salt away, so a High EC (unwashed) block is often the practical, lower-cost choice.
How washing brings EC down
Salts in coir pith are soluble, so they can be rinsed out. At SM Coir, pith for the Low EC block is washed on our own washing beds before it is dried, sieved and pressed. The High EC block skips this step.
| Feature | Low EC block | High EC block |
|---|---|---|
| Washing | Washed | Unwashed |
| EC | Less than 0.6 mS/cm | Not specified |
| pH | 5.5 – 6.5 | 5.5 – 6.5 |
| Typical use | Propagation, greenhouses, hydroponics | Soil conditioning, horticulture, landscaping |
Washing is not the same as buffering. Buffering treats the pith with a calcium solution so that calcium takes the place of potassium and sodium held on the fibre. If your crop or system needs buffered media, say so in your enquiry and ask how the supplier handles it.
What pH tells you
pH measures how acidic or alkaline the media is, on a scale where 7 is neutral. Most crops take up nutrients best when the root zone is slightly acidic, and a range of about 5.5 to 6.5 is a common target for soilless growing. Both SM Coir blocks are specified at pH 5.5 – 6.5, in every grade.
pH and EC work together. A media can sit in the right pH range and still carry too much salt, so read both numbers rather than either one alone.
Reading the numbers on a specification sheet
- Check the unit. EC should be in mS/cm or dS/m. A figure given in another unit cannot be compared directly.
- Ask how it was measured. EC and pH are read on a water extract of the media, and different extraction methods give different numbers for the same material. When comparing suppliers, compare like with like.
- Look at every grade. Fine, Standard and Coarse grades differ in expansion, moisture and fibre content. On our sheet, EC and pH are the same across all three grades of each product.
Checking a block yourself
You do not need a laboratory for a first check, just a calibrated EC meter, a pH meter and distilled water.
- Expand a sample of the block in water and let it settle, so you test the loose media rather than a compressed chunk.
- Mix a measured volume of media with distilled water, using the same ratio each time you test.
- Stir, leave it to stand, then strain off the liquid.
- Read EC and pH on the liquid with meters you have calibrated that day.
Keep a note of the ratio and the readings. The value of a home test is in comparing one delivery with the next, using the same method every time.
Which block to choose
- Propagation trays, seedling mixes, hydroponics, greenhouse grow bags: start with Low EC.
- Soil conditioning, landscaping, open-field beds: High EC is usually enough.
- Blending your own potting mix: either, depending on how sensitive the end crop is and how you will feed it.
If you are unsure, tell us the crop and growing system in your enquiry and we will confirm the product and grade on the quotation. You can compare every value grade by grade on our Products & Specifications page.
