Spawning and Spawn Run SOP — Dosage, Filling and Colonisation — India Setup Procedure & Equipment Cost

Step-by-step procedure

1. 1. Room preparation before compost arrives

   Wash the room, racks and floor with detergent, rinse, then disinfect with 2% formalin or a quaternary ammonium disinfectant. Cook-out the empty room at 65–70 °C for 8–12 hours if the previous crop had disease. Close the room and let it stabilise at 25 °C for 24 hours before filling. Check that door seals, drain traps and filter housings are intact — an open drain trap is a direct pathway for flies.

   • Room disinfected within 24 hours of filling
   • Cook-out at 65–70 °C after any diseased crop

2. 2. Spawn receipt, inspection and storage

   Buy grain spawn from a certified lab only. On receipt, inspect every bag: healthy spawn is uniformly white, smells of fresh mushroom, and shows no green, black or pink patches and no wet or slimy grain. Reject any bag showing off-colour. Store at 2–4 °C and use within 15 days of manufacture. Bring spawn to room temperature two hours before spawning — cold spawn added to warm compost condenses moisture on the grain and stalls the run.

   • Storage at 2–4 °C
   • Use within 15 days
   • Zero contaminated bags accepted

3. 3. Spawn dosage calculation

   Dose at 0.5–0.75% of wet Phase-2 compost weight, which is 5–7.5 kg of grain spawn per tonne. Use the higher end in winter, on a first crop in a new room, or where the compost is slightly cooler than ideal, because a higher dose colonises faster and gives competitors less time. Weigh the spawn — never estimate by bag count, because bag fill weights vary between labs.

   • 5–7.5 kg spawn per tonne of compost
   • Weighed, not estimated

4. 4. Mixing and filling

   Mix spawn through the full compost mass, not just the top layer. Machine mixing on a spawning line is ideal; hand spawning must be done in two passes with the compost turned between them. Fill the beds to 18–20 cm depth at 90–100 kg per square metre, level the surface, and press lightly to a firm but not compacted finish. Uniform depth across all seven tiers matters more than the exact figure, because temperature and airflow differ tier to tier already.

   • Bed depth 18–20 cm
   • 90–100 kg compost per sqm of bed
   • Depth variation under 2 cm

5. 5. Sealing and the first 72 hours

   Cover the beds with perforated polythene if the farm uses the sheet method, or maintain high humidity in the room if not. For the first 72 hours, hold compost temperature at 25 °C and do not open the room except for the daily inspection. This is when the mycelium establishes; every door opening drops humidity and pulls the surface dry.

   • Compost 24–25 °C
   • RH 90–95%
   • Minimum door openings

6. 6. Managing the colonisation heat load

   From Day 4 the mycelium generates its own heat, and compost temperature will run 2–3 °C above air temperature. Lower the air temperature to hold compost at 24–25 °C — do not let compost exceed 28 °C, which kills mycelium and favours competitors. This is the single most common spawn-run failure on Indian farms during April to June, and it is why refrigeration is sized on peak ambient rather than average.

   • Compost never above 28 °C
   • Air temperature 22–24 °C
   • Delta held by machine, not by opening doors

7. 7. Daily inspection and contamination response

   Inspect every bed daily with a torch. Healthy mycelium is bright white, cottony and advancing evenly. Green (Trichoderma), olive-brown (Chaetomium), or pink patches must be dealt with immediately: cover the patch with salt or lime, mark it, and record it. Do not disturb the patch or brush it — spores go airborne and reach every rack in the room.

   • Daily torch inspection of all tiers
   • Same-day response to any contamination

8. 8. Spawn run completion and handover to casing

   Spawn run is complete when white mycelium is visible throughout the bed depth and has reached the surface — typically 12–16 days. Confirm by opening a small section at three points per room. Do not case early: an incompletely run bed cased over will produce a weak, delayed and uneven first flush. Record the completion date and the observed uniformity before handing the room over to the casing SOP.

   • Full colonisation in 12–16 days
   • Verified at 3 points per room

Daily and per-cycle routine

• Record compost temperature at three tiers (top, middle, bottom) and both ends of each room twice daily.
• Log air temperature, RH and CO₂ every four hours from the controller or datalogger.
• Torch-inspect every bed once daily and photograph anything abnormal.
• Change footwear at the room entrance and use a fresh disinfectant foot dip per room.
• Keep a spawn traceability log: lab name, batch number, manufacture date, quantity used per room.
• Never move staff from a contaminated room into a clean room on the same shift.

Troubleshooting

How this SOP fits mushroom farming setup in India

Frequently asked questions