Why Coco "Steals" Calcium and Magnesium
Fresh coco coir contains sodium and potassium — residues from sea-water processing. When irrigated with a solution containing Ca and Mg, ion exchange occurs: coco releases Na and K and in return binds Ca and Mg from the solution. This process can continue for weeks.
Buffering Before Planting
Standard procedure:
- Soak in a Ca/Mg fertiliser solution (EC 2.0–2.5, Ca:Mg ≈ 3:1) for 8–24 hours
- Drain and rinse with clean water until drainage EC ≤ 1.0
Without buffering, the first 2–3 weeks are always unpredictable — you never know how much Ca and Mg the substrate is pulling from your solution.
Drainage EC as an Indicator
Normal range: drainage EC 0.3–0.5 above the input solution EC.
Measurement frequency: daily for the first two weeks, then once a week.
Three Mistakes That Cost the Most
- Skipping buffering — a plain water rinse does not substitute for buffering with Ca/Mg
- Not accounting for coco's Ca/Mg contribution in the recipe — properly buffered coco partially satisfies the plant's Ca and Mg demand
- Flushing on a fixed schedule rather than based on EC — flush only when drainage EC has actually risen
Signs the Substrate Is Ready
- Drainage EC ≤ 1.0
- Drainage pH 5.8–6.2