Compost Production SOP — Phase-1 and Phase-2 for Button Mushroom — India Setup Procedure & Equipment Cost

Step-by-step procedure

1. 1. Raw material intake and quality check

   Receive wheat straw in bales and store under cover on a raised, dry platform. Straw must be bright, dry, free of mould and not more than one season old. Poultry manure should be fresh broiler litter, not layer droppings with high grit content. Gypsum must be agricultural grade. Reject any consignment that is visibly mouldy or waterlogged, because contaminated straw carries competitor moulds through the entire cycle.

   • Straw moisture at intake below 15%
   • Poultry manure nitrogen 3.5–4.5% on dry basis
   • Gypsum purity 85%+

2. 2. Formulation and pre-wetting (Day 0 to Day 3)

   Work to a formula giving a starting C:N ratio near 28–30:1 and a finishing ratio near 17:1. A widely used Indian formula per tonne of dry wheat straw is 400–500 kg poultry manure, 30 kg urea, 25 kg gypsum and 30 kg wheat bran. Spread the straw on the wetting slab, soak it with clean water over two to three days until fully saturated, turning it once daily so the wetting is uniform. Water penetration into the stem is the objective — surface wetting produces dry cores that never ferment.

   • Moisture after pre-wetting 72–75%
   • No dry straw cores when a handful is squeezed

3. 3. Filling the aerated bunkers (Day 3)

   Fill the aerated bunker to a height of 6–7 ft over its underfloor aeration: 4-inch PVC pipes in the floor, fed from the 8-inch HDPE manifold. The 20 T unit's bunkers are 14 × 30 ft and the 30 T unit's 14 × 40 ft. Layer the manure and supplements evenly as the bunker is filled rather than dumping them at one end. Do not compact the fill — Phase-1 is aerobic and a compacted core goes anaerobic within 48 hours, producing black, foul-smelling compost that must be discarded.

   • Bunker core temperature reaches 70–75 °C within 48 hours

4. 4. Phase-1 turning schedule (Day 3 to Day 9)

   Turn on a fixed schedule, on Day 3, Day 5 and Day 7, moving the outside of the compost to the inside each time; between turnings the blowers run 5–10 minutes every 2 hours. Add gypsum at the second turning and the balance of water at each turning to hold moisture. Record the core temperature at three points before every turn. Phase-1 is complete when the compost is dark chocolate brown, the straw shears easily between the fingers, and the ammonia smell is strong but the material is uniform throughout.

   • Core temperature 70–78 °C between turns
   • Moisture 68–72% at the end of Phase-1
   • Phase-1 runs from Day 3 to Day 9 of the 15–16 day cycle

5. 5. Filling the Phase-2 tunnel (Day 9)

   Fill the pasteurisation tunnel or shelf room evenly to a bed depth of 1.8–2.0 m, without compaction. Uneven filling is the main cause of temperature stratification in Phase-2. Insert calibrated probes at three depths and at least three horizontal positions before sealing the tunnel.

   • Fill within 6 hours of emptying the bunkers
   • Bed depth variation under 10 cm

6. 6. Pasteurisation (Phase-2 part A)

   Raise the compost temperature to 58–60 °C and hold it for 6–8 hours with continuous air recirculation and a controlled fresh-air fraction. This kills nematodes, mites, competitor mould spores and weed mushroom mycelium. Never exceed 62 °C — above that, the thermophilic microflora that consumes ammonia is destroyed, and the compost becomes selective for competitors instead of Agaricus.

   • 58–60 °C compost temperature
   • Hold 6–8 hours
   • Air temperature never above 62 °C

7. 7. Conditioning (Phase-2 part B)

   Drop the compost to 45–50 °C and hold for 4–6 days with fresh air, allowing thermophilic actinomycetes to convert free ammonia into microbial protein. Reduce temperature by roughly 1 °C per day towards the end. Conditioning is finished when free ammonia is below 10 ppm — verifiable with a Drager tube or, as a field test, when a handful held to the nose has a sweet, bready smell with no ammonia sting.

   • 45–50 °C for 4–6 days
   • Ammonia below 10 ppm
   • Visible white actinomycete growth through the compost

8. 8. Cool-down and acceptance (Day 15–16)

   Cool the compost to 25–26 °C before spawning. Take five samples across the tunnel and check moisture, pH and ammonia. Compost is accepted for spawning only if all five samples pass. Record the batch number, formula, Phase-1 duration, peak temperatures and acceptance results in the batch file — this record is what allows a yield problem to be traced back to a cause three cycles later.

   • Spawning temperature 25–26 °C
   • Moisture 66–70%
   • pH 7.2–7.8
   • Ammonia under 10 ppm

Daily and per-cycle routine

• Record ambient temperature, bunker core temperature at three points and moisture observation every morning at 08:00.
• Photograph each bunker before and after every turning and file against the batch number.
• Check leachate drainage daily; standing leachate around the slab and bunkers breeds flies and re-infects the compost.
• Calibrate the temperature probes weekly against a reference thermometer.
• Wash and disinfect the loader bucket between the Phase-1 bunkers and the Phase-2 tunnel — this single step prevents most cross-contamination.
• Close the batch file at spawning with formula, durations, peak temperatures, acceptance results and the operator name.

Troubleshooting

How this SOP fits mushroom farming setup in India

Frequently asked questions