"Used a coco mat — radish lodged on day three. Switched to peat — basil germinates unevenly and the bottom layer turns sour."
Substrate choice depends on the specific moisture-holding capacity, capillarity, and aeration characteristics of each material.
Quick Glossary
- Jute — natural fibre mats; low water retention, good aeration
- Coco — coconut fibre; high water retention, requires buffering
- Peat — organic substrate; high water retention, acidic pH 3.5–4.5
- Foam — synthetic matrix; inert, stable geometry
Jute
Jute mat suits crops with cycles up to 7–10 days (radish, mustard, rocket). Advantages: no buffering required, good aeration. Downside: jute mats dry out faster than other substrates and require more frequent bottom watering.
Coco
Provides a larger moisture reserve for longer cycles. Requires buffering due to excess sodium and potassium. Quality varies significantly between batches in terms of density and capillarity.
Peat
Inexpensive, but has a natural pH of 3.5–4.5 and requires acidification correction to 5.8–6.5. With dense sowing, peat compacts and restricts oxygen access to the root. Mixing with perlite improves aeration.
Foam
A chemically inert matrix with no organic matter. Does not sour, contains no pathogens. Limitation: weak capillarity — requires direct water contact or top irrigation.
How to Choose
- Short cycle → jute
- Long cycle → coco
- Slow-growing crops → peat with perlite
- Automated systems → foam
Three Critical Mistakes
- Not checking pH before use
- Applying the same irrigation schedule to different substrate materials
- Cutting costs on material quality when scaling up
Signs That the Substrate Is Suitable
- Germination is even across the entire tray surface
- Root is white and odourless
- Bottom layer is moist but not wet
- Harvest is clean with no substrate material clinging to the product