Compost is misunderstood as a nutrient delivery system. Its more important function is inoculation — seeding soil with billions of organisms that rebuild the food web. The nutrient analysis of finished compost is modest. The biological analysis is extraordinary.
In Part 1 we covered the cast of soil organisms. This part covers how to grow them. We'll walk through the two major composting philosophies (hot and cold), the carbon-to-nitrogen ratio that governs which organisms dominate, a step-by-step 18-day Berkeley hot compost protocol, and how to make compost tea for rapid biological inoculation.
The Two Composting Philosophies
Not all compost is the same. The pile you build for your annual vegetable beds should be biologically different from the pile you build for your orchard understory. Here are the four main methods and when to use each.
| Method | Notes & Best Use |
|---|---|
| Hot / Thermophilic | 18–32 days to finished product; kills weed seeds and pathogens; high bacterial dominance; best for annual garden beds and fast fertility building |
| Cold / Fungal (slow) | 3–18 months; preserves fungal hyphae and protozoa; high humus quality; best for orchard understory, perennial beds, native plantings |
| Vermicompost (worm castings) | Pure bacterial + worm gut biology; highest plant-available nutrient density; best used as a top-dress activator rather than bulk amendment |
| Bokashi (fermentation pre-treatment) | Anaerobic fermentation of kitchen waste before hot or cold composting; increases bioavailability and reduces volume; excellent for meat/dairy scraps |
The C:N Ratio — Carbon and Nitrogen Balance
The C:N ratio governs which organisms dominate and how fast decomposition proceeds. The ideal starting ratio for hot compost is 25–30:1. For fungal / cold compost, 40–60:1. Here's where common homestead materials fall.
| Material | C:N Ratio | Notes |
|---|---|---|
| Wood chips (fresh) | 400–800:1 | High C — fungal food; use as mulch or base layer |
| Cardboard (plain) | 400–500:1 | High C — use as weed barrier under woodchips |
| Straw (wheat/oat) | 80–100:1 | High C — excellent fungal layer |
| Dry autumn leaves | 50–80:1 | High C — shred for faster breakdown |
| Coffee grounds | ~20:1 | Balanced; fungal-friendly; adds to acid beds |
| Green grass clippings | 15–20:1 | High N — activator layer; don't over-use |
| Vegetable kitchen scraps | 15–25:1 | Balanced N — core compost input |
| Fresh manure (cow, horse) | 15–25:1 | High N — powerful activator |
| Chicken manure (fresh) | 7–10:1 | Very high N — use in thin layers only |
| Comfrey (fresh leaves) | ~7:1 | High N + K + trace minerals — dynamic accumulator |
| Nettles (fresh) | ~5:1 | High N mineral accumulator — outstanding activator |
| Human urine (diluted 20:1) | ~1:1 | Extreme N — excellent activator or diluted liquid fertilizer |
Hot Compost — The 18-Day Berkeley Method
Goal: fast, hot, bacterial compost for annual garden beds. Kills pathogens and weed seeds.
Materials (per 1 cubic metre pile)
- ~60% carbon materials (straw, dry leaves, shredded cardboard, small wood chips)
- ~40% nitrogen materials (fresh manure, kitchen scraps, green material, nettles, comfrey)
- Handful of finished compost or garden soil as inoculant
- Water source nearby — pile should feel like a wrung-out sponge throughout
Day 1. Build the pile in alternating C:N layers ~30 cm each. Water each layer. Core temp should reach 55–65°C within 24–48 hours.
Day 4. First turn. Move outside to inside. Check moisture. If temp dropped below 45°C, add N. If above 70°C, add water and turn more thoroughly.
Days 7, 10, 13, 16. Turn every 3 days. Each turn re-heats the pile as fresh surfaces meet oxygen.
Day 18–21. Finished. Compost should smell like earth, be dark brown and crumbly, with no recognizable inputs. Apply directly or cure for 2–4 more weeks for maximum biology.
Temperature guide: 45–55°C = active mesophilic phase (rich diversity). 55–65°C = thermophilic phase (pathogen and weed seed kill). Above 70°C = too hot, biology dying — add water and turn immediately. Below 40°C = pile stalling — add an N source (urine, fresh manure, nettles).
Cold / Fungal Compost
Goal: preserve fungal networks. Best for orchard understory, hugelkultur beds, perennial zones.
- Build pile with high C:N ratio (40–60:1) — prioritize woody materials, straw, dry leaves
- Inoculate with mycelium: bury pieces of rotting wood found in forest, or purchase wine cap or oyster mushroom spawn
- Keep moist but never saturated — fungal hyphae need air
- Do NOT turn — turning destroys fungal networks. Let it sit 6–18 months
- Apply as thick mulch directly to perennial beds and tree bases, not dug in
- Woodchip mulch 10–15 cm deep around trees is essentially cold compost in progress
Compost Tea — Liquid Biology
Compost tea extracts and multiplies the biology from finished compost into a liquid that can inoculate large areas of soil quickly. Key for spring application to garden beds before planting.
Aerated Compost Tea (ACT) — 20 L recipe
- 1–2 cups mature compost in a mesh bag (like a tea ball)
- 1 tbsp unsulfured blackstrap molasses (bacterial food)
- 1 tsp liquid kelp (fungal food + minerals)
- Aerate with an aquarium pump for 24–36 hours at room temperature
- Apply within 4 hours of brewing — biology dies rapidly without oxygen
- Apply to soil surface at dusk or on overcast days (UV kills biology)
Apply compost tea to soil, not leaves, to avoid potential pathogen transfer. Dilute 5:1 with non-chlorinated water (let tap water sit 24 hours to off-gas). Do not use if it smells sulfuric — that is anaerobic and harmful.
Compost as Inoculant
Compost is not a bag of nutrients — it's a living community you grow on purpose. Build the right pile for the right zone, and the soil that surrounds it will inherit the biology. Part 3 shows how perennial systems use this biology to build soil continuously, with less labour every year.
The Living Soil Course · Part 2 of 6