Article 13 | Cannabis Cultivation Knowledge Series — Growing Media Comparison
Growing media (substrates) are the most critical foundation in cannabis cultivation. Whether growing in soil or hydroponic systems, choosing the right medium directly affects root structure, aeration, moisture retention, and final yield.
This article compares 9 main types of substrates, complete with scientific data, soil mixing formulas, and a detailed comparison table to help growers make informed decisions.
1. Organic Living Soil
Organic soil remains the most popular substrate, accounting for ~43.7% of the global cannabis cultivation market (2025).
Key Specifications
| Parameter | Value |
|---|---|
| CEC (Cation Exchange Capacity) | 50–150+ meq/100g |
| pH | 6.0–6.5 |
| WHC (Water Holding Capacity) | 60–80% |
| AFP (Air-Filled Porosity) | 10–20% |
Mycorrhizal Fungi
The fungus Rhizophagus irregularis (AMF) creates a mycelial network that expands the root’s nutrient absorption zone. Research from Frontiers in Plant Science (2022) shows that cannabis plants inoculated with AMF produce yields equal to or higher than plants fertilized with chemical NPK.
Trichoderma
Trichoderma longibrachiatum improves soil quality, decomposes organic matter, and competes with soil-borne pathogens.
Recommended Brands
- Fox Farm Ocean Forest
- Roots Organics Original
- BuildASoil 3.0
2. Super Soil Formulas
Subcool Formula (Updated) for 6–8 bags of organic soil
| Ingredients | Dosage |
|---|---|
| Worm castings | 25–30 lbs (~11–14 kg) |
| Bone meal (3-15-0) | 5 lbs (~2.3 kg) |
| Blood meal (12-0-0) | 5 lbs (~2.3 kg) |
| Bat guano (0-7-0) | 5 lbs (~2.3 kg) |
| Epsom salt | 3/4 cup |
| Dolomite lime | 1/2 cup |
| Azomite | 1/2 cup |
| Humic acid | 2 tablespoons |
Cooking time: 4–8 weeks — mix weekly
Coots Mix Ratios
33% peat moss : 33% aeration component : 33% compost/worm castings
Additive Table per cubic foot (28.3 liters)
| Additive | Dosage | Function |
|---|---|---|
| Neem meal | 1/2 cup | Pest control + slow-release nitrogen |
| Kelp meal | 1/2 cup | Potassium + growth hormones |
| Crustacean meal | 1/2 cup | Chitin + Ca + Nitrogen |
| Fish bone meal | 1/2 cup | Phosphorus + Calcium |
| Oyster shell | 1/2 cup | Calcium + pH buffer |
| Basalt rock dust | 1/2 cup | Trace minerals |
| Gypsum | 1/2 cup | Calcium + Sulfur |
| Malted barley | 1/4 cup | Breakdown enzymes |
| Biochar | 1–2 cups | Increases CEC, microbial habitat |
| Mycorrhiza | 1–2 tablespoons | Root zone microbial inoculation |
3. Coco Coir
Coco coir is the most popular alternative substrate in Drain-to-Waste (DTW) systems.
Technical Specifications
| Parameter | Value |
|---|---|
| CEC | 10–30 meq/100g (buffered) |
| WHC | 73–88% |
| AFP | 15–35% |
| pH | 5.5–6.5 |
| Water Absorption | 8–9 times its weight |
| Reusability | Yes, 2–3 cycles |
Quality Assessment via EC
| Grade | EC (mS/cm) | Status |
|---|---|---|
| Raw | 2–6 | Too high — unusable |
| Washed | <1 | Usable |
| Premium | ≤0.5 | Excellent quality |
Calcium Buffering
Use Ca(NO₃)₂ at 7 kg per 1,000 liters of water, soak overnight — to flush out excess sodium and potassium.
Recommended Brands
- CANNA Coco Professional Plus
- Char Coir
- Mother Earth Coco
- Botanicare Cocogro
4. Perlite
Perlite is expanded volcanic rock used to increase aeration in soil mixes.
Grain Sizes and Applications
| Type | Size | Application |
|---|---|---|
| Fine | <3 mm | Seed starting |
| Medium (#3) | 3–6 mm | Mixed with soil/coco |
| Coarse (#4) | 6–13 mm | Hydroponics |
Specifications
| Parameter | Value |
|---|---|
| WHC | 20–35% |
| AFP | 30–55% |
| CEC | ~0 |
| pH | 6.5–7.5 |
Mixing Ratios
- Mixed with soil: 20–30%
- Mixed with coco: 30–50%
- Hempy bucket: 100%
5. Vermiculite vs. Perlite
| Property | Perlite | Vermiculite |
|---|---|---|
| CEC | ~0 | 100–150 meq/100g |
| Drainage | Excellent | Poor |
| Water Retention | Low–Medium | High (50–70%) |
| Aeration | Excellent | Medium |
| Best Fit | Most cannabis cases | Seed starting, dry climates |
6. Rockwool (Mineral Wool)
Rockwool is a staple substrate in commercial hydroponic systems.
Specifications
| Parameter | Value |
|---|---|
| Total Porosity | 96% |
| AFP | 11–15% |
| WHC | 75–91% |
| CEC | 0 |
| pH (untreated) | ~8.0 |
| Reusability | 3–6 cycles |
Pre-treatment
Must be soaked in a pH 5.5 solution before use.
Recommended Brands
- Grodan Hugo / Delta blocks
- Cultilene
- FloraFlex Wool
- VidaWool
Environmental Issues
Rockwool is not biodegradable. Germany and Austria are moving toward banning mineral wool in agriculture.
7. LECA / Clay Pebbles
| Parameter | Value |
|---|---|
| WHC | 10–25% |
| AFP | 35–50% |
| CEC | ~0 |
| pH | ~7.0 |
| Reusability | Permanent |
Best Fit: Ebb & flow systems, recirculating DWC
Recommended Brands
- Mother Earth Hydroton
- Grow!t
- GEOLITE
8. Alternative Substrates (2024–2026)
Parboiled Rice Hulls (PBH)
- AFP: 70%
- WHC: ~23%
- Rich in silica, helps strengthen stems
- Currently replacing perlite at many farms
Pumice
- WHC: ~30%
- AFP: 30–50%
- Permanently durable, heavier than perlite
- Suitable for outdoor growing and high-wind areas
Biochar
- CEC: 15–300+ meq/100g
- Carbon-negative emission
- Mix 5–20% into soil
- Biochar + Trichoderma = 101% increase in tomato yield
9. Comprehensive Comparison Table
| Substrate | WHC% | AFP% | CEC | pH | Reusability |
|---|---|---|---|---|---|
| Soil (peat) | 60–80 | 10–20 | 50–150 | 6.0–6.5 | Limited |
| Coco Coir | 73–88 | 15–35 | 10–30 | 5.5–6.5 | 2–3 cycles |
| Perlite | 20–35 | 30–55 | ~0 | 6.5–7.5 | Limited |
| Vermiculite | 50–70 | 8–15 | 100–150 | 6.0–7.5 | Limited |
| Rockwool | 75–91 | 11–15 | 0 | 7.0–8.0 | 3–6 cycles |
| LECA | 10–25 | 35–50 | ~0 | 5.5–6.5 | Permanent |
| Rice Hulls | 20–23 | 69–70 | 2–10 | 5.5–6.5 | No |
| Pumice | 25–40 | 30–50 | 5–15 | 6.5–7.5 | Permanent |
| Biochar | 40–60 | 15–30 | 15–300+ | 7–10 | Yes |
10. Matching Substrate to System
| Substrate | DTW | Recirculating | Water-only |
|---|---|---|---|
| Coco + Perlite | Best | Not recommended | No |
| Rockwool | Good | Best | No |
| LECA | Medium | Best (ebb & flow) | No |
| Living Soil | Okay | No | Best |
Coco : Perlite Ratios
| Ratio | AFP | Application | Watering Frequency |
|---|---|---|---|
| 70:30 | 25–30% | Industry standard | 1–2 times/day (manual), 3–6 times (auto) |
| 60:40 | 30–35% | High-frequency auto | 6–12 times/day |
| 50:50 | 35–40% | Dutch-style commercial | Mandatory auto |
11. Environmental Sustainability
| Substrate | CO₂e/m³ | Main Concerns |
|---|---|---|
| Compost | 20–50 kg | Local production |
| Rice Hulls | 10–30 kg | Agricultural byproduct |
| Biochar | Negative | Local production dependency |
| Coco Coir | 50–100 kg | Long-distance transport |
| Perlite | 150–300 kg | Mining + 850°C furnace |
| Peat Moss | 200–500 kg | Destruction of peat bogs |
| Rockwool | 150–250 kg | 1,500°C melting, non-degradable |
Conclusion
No single substrate is best for every situation — it depends on your growing system, budget, experience, and sustainability goals.
- Beginners: Pre-packaged organic soil or 70:30 coco + perlite
- Organic Growers: Super Soil / Coots Mix + Living Soil
- Commercial Hydroponics: Rockwool or 50:50 coco + perlite
- Sustainability: Rice hulls + biochar + local compost
Disclaimer
This article is for educational and research purposes only. Cannabis cultivation in Thailand is governed by the Controlled Herbs Act 2025 and Ministerial Regulation B.E. 2569 (effective April 2026). Growers must possess a valid license.
References
- HortGrow Solutions (2025). Coco Coir CEC & Buffering Guide
- Frontiers in Plant Science (2022). AMF vs NPK in Cannabis sativa
- Malik P, Tlustos P (2025). Agriculture 15(18):1955
- Gachukia & Crouse (2008). HortTechnology (ASHS)
- NorCal Perlite. Pumice vs Perlite Technical Comparison
- PT Horticulture. Growing Media Guide
- Grodan. Recycling Programs for Mineral Wool
- Viet Growers Community (2015). Viet Grower Handbook
Posted by AZ_Growshop_Asia — asiannabis.com
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