Building Your Own Super Soil

What super soil actually is

Super soil is a heavily amended organic potting mix designed to supply most or all of a cannabis plant's nutrients through microbial activity rather than liquid feeding. The grower combines a base potting soil with concentrated organic amendments (guanos, meals, minerals, compost), then lets the mix 'cook' — meaning microbes break amendments down into plant-available forms — for several weeks before use Weak / limited^[1][2].

The term was popularized by breeder Subcool (TGA Genetics), whose published recipe in Dank: The Quest for the Very Best Marijuana became the template most growers riff on ^[1]. Conceptually it overlaps with the broader practice of Living Organic Soil, which emphasizes a permanent soil web rather than one-shot amendments.

Why growers use it

The main reasons are practical, not mystical:

• Simpler feeding. Once cooked, you mostly water with plain pH-adjusted water. No mixing nutrient schedules every few days.
• Forgiving pH buffering. Organic matter and humus buffer pH swings better than inert media Strong evidence^[3].
• Reusable. A super soil bed can be re-amended and reused for years, lowering long-term cost.
• Flavor and aroma claims. Many growers report richer terpene profiles from living soil. Controlled comparisons are scarce; treat this as Anecdote.

What super soil does not do: it does not produce inherently bigger yields than a competently run synthetic or hydroponic system. Peer-reviewed comparisons of organic vs. conventional cannabis nutrition are limited, and results are mixed Weak / limited^[4].

When to start

Start mixing 4 to 8 weeks before you plan to transplant into it. Amendments need time and biology to convert into plant-available nutrients; using uncooked super soil on young plants will almost always burn them.

Temperature matters. The pile cooks faster at 20–30 °C (68–86 °F) and stalls in cold garages. Check it weekly — it should smell earthy (like forest floor), feel warm in the center during the first 2 weeks, and stop heating up before you use it Weak / limited^[1].

How to build it: step by step

This is a generic Subcool-style recipe, scaled per ~1 cubic foot (~28 L) of base soil. Wear a dust mask when handling dry amendments ^[5].

1. Gather a base soil. Use a quality peat- or coco-based organic potting mix with perlite. Avoid mixes pre-loaded with synthetic time-release fertilizer.

2. Add amendments per cubic foot of base soil:

• 1.5 lb (680 g) high-N bat guano or fish meal
• 1.5 lb (680 g) blood meal or additional fish meal
• 2–3 lb (~1 kg) bone meal or fish bone meal (P, Ca)
• 1 cup kelp meal (K, micros)
• 1 cup dolomite lime (Ca, Mg, pH buffer)
• 1/2 cup Epsom salt (Mg)
• 1/2 cup azomite or basalt rock dust (trace minerals)
• 2 tbsp powdered humic acid
• 25–50% by volume good compost and/or worm castings

Quantities vary across published variants; the above is representative, not sacred ^[1][2].

3. Mix thoroughly. Spread a tarp, layer the base soil and amendments, and turn it like you're folding dough until evenly distributed.

4. Moisten and pile. Water until the mix is damp but not dripping (squeeze test: a clump holds, no water runs out). Pile it into a tote or trash can with a loose-fitting lid — not airtight.

5. Cook for 30–60 days. Turn the pile every 1–2 weeks. The center will warm up, then cool. When it stops heating and smells sweet and earthy, it's done Weak / limited^[1].

6. Use it layered, not pure. Most growers fill the bottom one-third to one-half of a finishing pot with super soil and top with plain organic soil, so roots grow into the hot layer as the plant matures. Seedlings and clones go into the plain top layer ^[1].

Common mistakes

• Planting seedlings directly in pure super soil. Almost guaranteed nitrogen burn. Layer it, or transplant only well-established vegging plants.
• Skipping the cook. Fresh amendments, especially blood meal and high-N guano, will scorch roots and stink.
• Sealing the container. Anaerobic conditions produce ammonia and sour, putrid smells. Use a breathable cover.
• Adding bottled nutrients on top of super soil. You usually don't need them, and salt-based feeds can suppress the microbial life you spent weeks building Weak / limited^[3].
• Chasing pH with liquid pH-down every watering. Let the dolomite and organic matter buffer it. Use a pH meter to confirm runoff is roughly 6.2–6.8, but don't micromanage.
• Ignoring pests in the soil. Hot, moist organic mixes attract fungus gnats. Top-dress with a thin layer of dry mulch (e.g. rice hulls) and consider beneficial nematodes or Bacillus thuringiensis israelensis Strong evidence^[6].

Related techniques

• Living Organic Soil (No-Till) — the longer-term evolution of super soil, focused on a permanent soil web.
• Top-Dressing and Teas — how to maintain a super soil bed across multiple grows.
• KNF and JADAM — Korean Natural Farming approaches that overlap philosophically.
• Coco Coir Growing — a simpler inert-media alternative if super soil sounds like too much work.

If you've never grown cannabis before, start with a quality bagged organic soil and light bottled feeding, then graduate to building your own mix on your second or third grow.

Sources

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