Running a commercial crop

Every load DMR publishes is per square metre of bed. In the first two flushes a bed makes about 10 g of carbon dioxide per square metre every hour, about 10 W of heat per square metre, and loses about 31 g of water per square metre every hour at 17 C and 85 per cent humidity.

So if you add a tier and increase bed area, you increase cooling, ventilation and humidification duty in the same proportion. The machine does not know you added shelves.

DMR's project model assumes six crops of 60 days per room per year.

Uneven filling is a common cause of staggered flushes. Compost depth, compaction and casing thickness must be the same from the first tray to the last.

Casing thickness is worth agreeing in writing, because DMR's manual defines casing as a 3 to 4 cm layer in one paragraph and instructs a 4 to 5 cm application a few lines later. Pick one figure for your farm and hold it.

A bed that is deeper at one end runs warmer there, pins later and is picked later, so one room then needs two climate decisions at once.

Walk the loaded room before the crop starts and find the places where you feel no air.

A unit growing in a 60 by 18 foot room, the size MIDH costs in its production unit norm, added two rows against the back wall to use spare compost.

Those rows sat past the end of the duct run. They read 2 C warmer, pinned two days late, and after a normal watering the caps there stayed wet longest, which is the blotch condition.

The operator did not change the set point. He pulled the rows back, cleared the return, remeasured at bed height and wrote the new layout into the room file.

Casing a block that is not fully run buries live but unspread mycelium, and the crop comes late and uneven. Check several trays across the room, including the coolest end, before you decide.

Case run is held at 23 to 25 C air with about 95 per cent humidity, and DMR notes that no fresh air is given, so carbon dioxide reaches around 7500 ppm. Case run is about 7 days.

The evidence to vent is mycelium visible at the casing surface across the room, not the seventh day on a calendar.

Check casing moisture at the same time, because the casing carries the crop through pinning at 48 to 52 per cent. A dry casing at venting will pin thinly however good the air settings are.

At venting you choose a schedule and commit to it. Air comes down towards the fruiting band, carbon dioxide to 800 to 1000 ppm, and humidity from about 98 down to 92 per cent.

DMR expects pinheads 3 to 4 days after venting. If nothing shows by day five, the answer is in your own record: was the mycelium really at the surface, did carbon dioxide actually fall, was the casing dry.

Changing three settings at once at that moment destroys the evidence. Change one thing, wait the published time, and write down what happened.

An operator should be able to defend every transition a week later. A short note does it.

Write the date and time, what was measured and where in the room, what the crop looked like in at least three places, which schedule you chose, what you expect within 72 hours, and what observation would prove you wrong.

That last line is the valuable one. If you expect pins in four days and none appear, the note tells you exactly which assumption failed, instead of leaving the whole crop open to guesswork.

Three published facts guarantee variation. The bed runs 1 to 2 C above the air around it. Air leaves the handling unit at 14 C to deliver 17 C at the bed, so it warms along its path. Air speed at the bed is limited to 15 cm per second, so the far end gets whatever is left.

Add a door that opens on to a warm corridor, tiers at different heights, and beds of different depth, and one room easily holds two climates.

The controller shows one number because it has one sensor. That number is a place, not a room.

Take three positions along the room, near the unit, middle and far end, at three heights, bottom, middle and top tier. That is nine points.

At each point record air temperature, bed temperature, humidity, carbon dioxide if you have a meter, and whether you can feel air movement. Use the same instrument, the same person and the same time of day, because the comparison matters more than absolute accuracy.

Write the nine readings on a grid drawn in the room file, not on a loose slip, so the next crop can be compared with this one.

A spread of more than a degree or two between points, a corner sitting outside the 80 to 85 per cent humidity band, or carbon dioxide well above the 1000 to 1500 ppm cropping band at the far end all say the same thing: the room is not distributing what the machine is making.

That is a baffle, duct, deflector or loading problem. Changing the set point to fix it only moves the whole room, and usually makes the good end wrong as well.

Fix distribution first, then set points, then blame the equipment.

Map at least three times in a crop: at venting, during the first flush and during the third flush, when air changes drop from 6 to 4 per hour.

Keep the same nine points every time. A map that moves cannot be compared.

Then put the crop beside the climate. Record picked weight by position, not just by room. If the far end gives less weight at every mapping, you have evidence that survives an argument, and a target for the next shutdown. Photograph the grid sheet at the end of each crop and keep it with the room file.

So the operator's first move is to close the information gap: readings at the affected position and at a clean position in the same room, taken with the same instrument, in the same hour.

These steps cost nothing and are never wrong. If the problem turns out to be watering rather than disease, you have lost one morning of convenience. If it is disease, you may have saved the rest of the crop.

Some problems set the clock. DMR states that dry bubble, left uncontrolled, can destroy a crop in 2 to 3 weeks, so it outranks a slow quality complaint.

Bacterial blotch needs 20 C with a water film on the cap for more than about three hours, which is something you can end this afternoon with air movement and watering discipline. False truffle appears above 23 C.

For flies, DMR's thresholds decide: any live adult in the first flush, or more than 20 catches per trap per week from the second flush onwards, is an action point.

Two boundaries are not the operator's to move. The first is chemical: this course prints no product names or doses, approvals change, and mushrooms are eaten fresh. Check the current label approval for mushrooms in India and your state advisory, and remember NHB's minimum 48 hour gap between spray and picking.

The second is the end of the crop. NHB records a cook out at 70 C held for 12 hours for pathogens, and 2 to 3 hours for insects, with spent compost buried under at least 10 cm of manure.

A suspect crop is finished properly, not quietly emptied.