A super soil is a base mix plus compost, aeration, minerals, nutrient meals, and microbes. It feeds one cannabis plant for one grow cycle with plain water. Six parts matter. There is no single standard recipe.
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Base mix
Peat moss or coconut coir holds water and anchors roots. Peat runs acidic, pH 3.5 to 4.5, so it needs lime. Coir sits near pH 6.0. A common split is one third base by volume.
Humus: compost and worm castings
Compost and worm castings supply humic acid, nitrogen, and bacterial life. Use one third by volume. Mature compost smells earthy and holds a carbon to nitrogen ratio near 20 to 30 to 1. Immature compost burns roots. Buy from a supplier that posts an analysis, or make your own pile and let it cure.
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Aeration
Perlite, pumice, or rice hulls drain water and let oxygen reach roots. Target 20 to 30 percent of total volume. Roots respire. Waterlogged soil kills them.
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Mineral content
- Dolomite lime: 1 to 2 cups per cubic foot. Raises pH and adds calcium and magnesium.
- Gypsum: 1 cup per cubic foot. Adds calcium and sulfur. Holds pH steady.
- Rock phosphate: 2 to 4 cups per cubic foot. Slow release phosphorus.
- Glacial rock dust or azomite: 1 to 2 cups per cubic foot. Trace elements.
Nutrient meals
- Blood meal: 1 cup per cubic foot. Nitrogen, short chain.
- Bone meal: 2 cups per cubic foot. Phosphorus and calcium.
- Kelp meal: 0.5 cup per cubic foot. Potassium plus cytokinins.
- Neem meal or alfalfa meal: 0.5 to 1 cup per cubic foot. Nitrogen and pest pressure.
Brands differ in grind and moisture. Follow each label.
Microbes
Bacteria and fungi break meals into ions roots absorb. Mycorrhizal fungi colonize root tissue and extend reach for phosphorus and water. Add inoculant at planting, or mix 1 to 2 cups of fresh castings into the planting hole. Chlorine off gasses from tap water in 24 hours. Chloramine does not off gas, so pass it through a carbon filter.
Cooking time
Mix the batch, moisten to field capacity, and rest it 30 to 60 days at 70 F to 80 F. Microbes consume the raw meals during that window. Turn the pile once a week. An unfinished mix can burn seedlings.
pH and water
Target soil pH 6.0 to 7.0. Water at 6.2 to 6.8. Plain water covers the full cycle if the mix is rich. Some growers top dress in week 5 of flower.
Testing
Send a sample to a soil lab for a saturated paste or Mehlich-3 test. Ask for pH, EC, nitrate, phosphorus, potassium, calcium, magnesium, and sodium. Public research on cannabis fertility is thin. The plant stays under federal control in the US, so most super soil recipes come from grower trials, not university field data.