Compost, step by step

Straw and manure deliveries vary in moisture, structure and composition. Record the source, receipt date, storage condition and as-received weight of each lot. A formula copied as truckloads or bags can change substantially when a new supplier delivers wetter or denser material. Keep the weight basis visible whenever you compare two recipes.

Use one documented formulation suited to the available process. List what each ingredient contributes and who may authorise substitutions. If laboratory results are available, record the test method, sample identity and whether values are expressed on a wet or dry basis. A chemical analysis cannot replace physical structure: air still needs pathways through the prepared mass.

During wetting, assess uniformity across the material. Water that drains away does not become useful substrate moisture, and visibly wet outer straw does not establish that the centre is equally wetted. Record additions and representative checks so the next operator understands how the batch reached its present condition.

For a hypothetical 100 kg lot containing 30% moisture on a wet basis, dry matter is 70 kg. A second 100 kg lot at 50% moisture contains only 50 kg dry matter. The truck weight is identical, but the amount of dry material differs. This explains a mass balance; it is not a compost recipe.

• Dry matter = wet mass × (1 − moisture fraction)
• 100 × (1 − 0.30) = 70 kg
• 100 × (1 − 0.50) = 50 kg

The first phase changes the raw material through microbial activity. Temperature is one sign of that activity, but a high peak does not describe the condition of the whole mass. Record several positions and interpret the pattern with moisture, structure, additions and turning or aeration events. Keep sensor location on the same chart as the reading.

Compare what happened before a change. Did the batch become compacted? Was a different lot introduced? Did aeration stop? Was water added unevenly? These questions help decide what evidence is missing before an operator changes the process. Follow the established method for the system; an outdoor heap and an aerated bunker should not be forced into one identical calendar.

Phase II is a controlled treatment of the compost with more than one objective. The pasteurisation stage and subsequent conditioning have different purposes. Completing a heating stage is therefore not, by itself, permission to add spawn. The process must also produce a suitable, conditioned material and bring it to the appropriate spawning condition.

Uniform loading and airflow matter because the air display and the coldest or warmest material location can differ. A time-and-temperature record should identify its measurement points. Record interruptions and corrective action instead of concealing gaps in the chart. Tunnel and steam-system operation needs a trained operator and a process suitable for the actual load and equipment.

At release, use the defined specification for the selected compost system, including its ammonia assessment, temperature, moisture and physical condition. Do not use a deliberate smell test to establish gas safety or substitute for the relevant measurement. Store the release decision with the batch, and keep unresolved material separate from accepted material.

If colonisation is poor, compare retained records from successful and unsuccessful batches. Start with delivered raw materials, moisture basis, mixing, loading, process continuity, cooling and transport. Then check spawn, handling and the receiving grow room. Altering the nitrogen addition immediately can hide a process or handling failure and create a new variable in the next batch.

Make the review specific enough to change one future decision. ‘Compost bad’ is not useful; ‘rear sensor remained cooler after filling density changed’ is an observation that can be investigated. Record the proposed change, its reason and what result would support or contradict the explanation. Use the testing and process-control guides for the relevant measurements.

Every compost mix has four jobs. Straw supplies carbon, the energy food of microbes, and the open structure that lets air move. Chicken manure, wheat bran, oil cakes and fertilisers such as urea or calcium ammonium nitrate supply nitrogen, the protein food. Gypsum is the conditioner: it keeps the mass open and adds calcium. Water carries everything.

If you buy a material without knowing its job, you cannot repair the mix when one job falls short. Wheat straw, paddy straw and farmyard manure are what most Indian yards actually have, so plan around them.

The ICAR-DMR raw material table gives typical dry weight values: wheat straw about 0.6 per cent nitrogen, deep litter chicken manure 3.0 per cent, wheat bran 2.0 per cent, soybean meal 6.5 per cent and cotton seed meal 7.0 per cent.

These are typical values, not your values. A worked example in the same chapter uses chicken manure at 2.6 per cent and straw at 0.40 per cent. Manure from a young flock on fresh litter is not manure scraped off a shed floor after a year. Start from the table, then test your own lot when a laboratory is reachable.

Judge every delivery before it is tipped. Straw should be bright, dry, springy and free of black or grey mould. A sour cellar smell means it has already fermented and lost carbon you paid for. DMR asks for freshly harvested material chopped to about 5 to 8 cm. Manure should be crumbly, not a slurry.

• Look: colour, mould patches, foreign matter, soil.
• Feel: dry and springy, or damp and matted.
• Smell: clean straw, not sour or mouldy.
• Weigh it yourself; do not count trolleys.
• Log supplier, date, weight and condition.

A formula is arithmetic done on particular materials. If your manure holds less nitrogen than the manure it was written for, the same weights give a weaker mix, the heap heats poorly and moulds that live on carbohydrate move in. If it holds more, nitrogen escapes as ammonia and yellow moulds follow.

Size matters too. DMR warns against composting less than 300 kg of base material, because a smaller pile cannot hold the temperature it needs. Keep a lot record so next season you can explain a good batch and a bad one.

DMR sets the compounding mixture at 1.5 to 1.75 per cent nitrogen on a dry weight basis at stacking. The mineral table in the same chapter prints 1.5 to 1.8 per cent, so treat the upper edge as soft and never round upward on purpose.

The second target is the carbon to nitrogen ratio, written C:N. It is adjusted to 25 to 30 parts carbon for each part nitrogen at stacking, and falls to about 16:1 in finished compost. Both targets describe one mix from two sides: how much protein food is present, and how much energy food sits around it.

The formulation DMR calls widely used in India, for the short method, is wheat straw 1000 kg, chicken manure 500 kg, urea 15 kg, wheat bran 75 kg and gypsum 30 kg. The DMR indoor method uses wheat straw 1000 kg, poultry manure 500 kg, wheat bran 70 kg, cotton seed cake 20 kg and gypsum 40 kg.

As a rule of thumb DMR gives 0.7 to 0.8 tonne of chicken manure and 0.05 to 0.15 tonne of gypsum per tonne of straw, gypsum going in at the third turning. Older formulae also list BHC or lindane, an insecticide now banned in India. Read those lines as history.

Take each material, convert its wet weight to dry weight using its moisture, multiply the dry weight by its nitrogen per cent, and add the results. Divide that total by the total dry weight and you have the nitrogen of your mix.

If the answer lands below the band, add a nitrogen carrier such as bran, an oil cake or a nitrogen fertiliser. If it lands above, add straw rather than cutting manure to nothing, because straw is also your structure. Write the assumed nitrogen of every material beside the sum.

Below 1.5 per cent nitrogen, DMR reports that the compost does not ferment properly, the heap may not pass 55 to 60 degrees Celsius, and moulds such as Stachybotrys move in.

Above 1.75 per cent the ratio is wrong, more nitrogen escapes as ammonia, and the yellow mould Sepedonium often follows and can cut yield badly. The method also shows in the finished nitrogen: DMR reports about 1.75 to 2.0 per cent for long method compost, 2.0 to 2.2 for the short method and 2.2 to 2.5 for indoor compost.

Dry straw will not ferment. DMR wets straw on a platform for 24 to 48 hours until it reaches about 75 per cent moisture, and puts the water requirement at around 4000 litres per tonne of raw material. Run the leachate back over the heap instead of letting it drain away, because it carries nutrients with it.

Straw takes water slowly. A single soaking on the morning of stacking wets the outside and leaves the middle of each bale dry, and that dry core never joins the process. Give pre-wetting its own day in the schedule.

Moisture is not a single target. DMR reports about 72 to 75 per cent at the end of Phase I, when drops appear between the fingers on squeezing, and 64 to 66 per cent after Phase II, when no liquid oozes even on firm squeezing.

Long method compost at spawning is different again: 68 to 72 per cent for synthetic compost and 65 to 67 per cent where horse manure was used. The farmer folder gives 68 to 70 per cent on the squeeze test on day 28. Always say which compost and which stage before quoting a moisture figure.

The squeeze test is quick. Take a fistful, close the hand hard and read what happens: free running water means too wet, several drops between the fingers is Phase I level, a damp mass with no liquid is Phase II level.

If you have a balance, dry a known weight of compost until it stops losing weight and calculate the loss as a percentage. That is a real number, and it is the one to write down.

• Sample five points: both ends, both sides, centre.
• Take each sample from inside, not the dry surface.
• Use the same points every batch so readings compare.

Above 72 per cent at spawning, DMR reports that aeration fails, anaerobic conditions can kill the mushroom mycelium, and brown and white plaster moulds appear. Wet compost is also heavy and packs down, which blocks the air a blower is paid to deliver.

Dry compost fails the other way. NHB, reproducing ICAR guidance, links compost below 64 per cent moisture, under a wet casing layer, to weeper mushrooms. Correct water at a turning, where it can be mixed in, rather than pouring it on a filled bed later. Both faults cost the crop, and both are cheaper to prevent than to repair.

Composting is a relay. Mesophilic organisms, which live at everyday temperatures, start on the easy sugars as soon as straw is wet and nitrogen is available. Their own heat then pushes them out and hands the heap to thermophilic bacteria, fungi and actinomycetes, which prefer high temperatures and break down tougher material.

That is why a heap which will not heat is a feeding problem, not a heating problem. DMR notes that when nitrogen is kept below 1.5 per cent the heap may not pass 55 to 60 degrees Celsius, because there is too little microbial activity to make the heat.

In the long method the heap rises quickly and may reach 70 degrees Celsius within 24 to 48 hours. The DMR farmer folder describes 65 to 70 degrees in two or three days and calls it a good sign.

There is an upper limit. DMR states that above 80 degrees in the central core is not desirable, because the core goes anaerobic and the friendly thermophilic flora is lost. A heap hot in the middle and cold at the edges is not composting evenly; it is two heaps in one, and the turning schedule exists to swap them.

Good compost is not just rotted straw. It is food that Agaricus bisporus can use and most of its competitors cannot. That selectivity is built in Phase II, where thermophilic organisms take up the free ammonia and lock it into their own bodies as microbial protein.

DMR keeps the mass at 45 to 52 degrees Celsius for that conversion, and warns against conditioning below 40 degrees because mesophilic fungi set in and make the compost unsuitable. The conditioning band is not comfort; it is the range where useful organisms beat the others.

Microbial work burns material. DMR reports about 30 per cent weight loss in Phase I and a further 20 to 25 per cent in Phase II. The carbon to nitrogen ratio falls from 25 to 30 at stacking to around 16 to 1, and nitrogen per cent rises as carbon leaves as carbon dioxide.

This is why finished compost weighs far less than the straw you bought, and why nitrogen readings climb without anyone adding nitrogen. Expect the loss, plan for it, and do not read a rising nitrogen figure as proof of supplementation.

Stack on a clean cemented yard so leachate can be collected and returned. Stack size is set by climate, not by convenience. In the plains DMR recommends a stack about 100 to 120 cm wide and around the same height. In the hills, where outside air may sit between 7 and 20 degrees Celsius, the stack is widened to 130 to 150 cm with a height of about 150 cm so heat is not lost.

Keep the sides vertical and the top flat, press the edges lightly, leave the core loose, and never stack less than 300 kg.

A turning mixes the hot core with the cool edges, lets fresh air in, and re-wets what has dried. The DMR long method schedule gives turnings on days 6, 10, 13, 16, 19, 22 and 25, with filling on day 28, and gypsum going in at the third turning. The Hindi farmer folder prints an eight turning version of the same ladder.

Both DMR documents also call for an insecticide at the last turning, and they differ from each other by a factor of ten on strength. Copy neither. Check what is approved for this use today and follow that label.

Phase I compost is not finished compost. DMR describes it as dark brown, smelling heavily of ammonia, holding 72 to 75 per cent moisture, with pH roughly 8.2 to 8.5, nitrogen between 1.5 and 2.0 per cent and free ammonia around 800 to 1000 ppm.

That ammonia is the point. It is exactly what Phase II has to convert, and compost handed over with too little of it has already lost nitrogen to the air. If the smell is weak and the pH low, look back at the formula rather than pushing on.

A Phase I bunker is a walled concrete box with an aerated floor. A fan pushes air into a space under the floor, called the plenum, and the air rises through slots into the compost above. A timer runs the fan in cycles so the mass stays aerobic without being cooled too far.

The gain is time and control. DMR completes Phase I in a bunker in 6 to 8 days against 10 to 12 outdoors, and the whole indoor route runs 10 to 12 days. MIDH treats the Phase I bunker as one line inside a compost making unit costed at 30 lakh rupees.

Air is lazy. It leaves by whichever route has least resistance, so an uneven fill quietly starves part of the batch. A corner packed tight by a loader bucket stays cold and wet. A dip in the surface becomes a chimney, and air races out of it without touching the compost beside it.

Fill evenly, keep the surface level, and do not press the mass against the walls. Material wetter than planned will settle and compact on its own, so wet batches need more care with fill height, not more fan speed.

The one airflow figure DMR gives for Phase I is 10 to 15 cubic metres of air per tonne of wet compost per hour through the stack. That is delivered air, not the number printed on the fan.

DMR does not publish a bunker fill height, a plenum pressure or a timer cycle for Indian bunkers, so those must be established on your own farm and written down. Start from the supplier's commissioning settings, change one thing at a time, and keep the batch record that lets you compare one run with the next.

One probe in the middle tells you about the middle. Build a fixed grid instead: readings near each wall, in the centre, at two depths, taken at the same hours every day.

What you are looking for is spread, not a single value. A wide spread means air is not reaching everywhere, and the fix is usually the fill or a blocked floor slot rather than the fan. Use your nose as a second instrument: sharp ammonia is normal in Phase I, while a sour or rotten egg smell says a pocket has gone anaerobic.

A fan is rated at a test condition with nothing in its way. In a real bunker or tunnel the air must pass through a plenum, a slotted floor and one to two metres of damp compost. Each of those adds resistance, and the fan moves less air as resistance rises.

The figure that matters is air passing through the stack. DMR states 10 to 15 cubic metres of air per tonne of wet compost per hour for aerated Phase I. Work out what your batch weighs, multiply, and compare that with what the system is actually delivering before blaming the compost.

Air is the means; oxygen is the purpose. DMR asks for oxygen above 10 per cent by volume during Phase II conditioning so the mass stays fully aerobic, and notes demand can climb above 15 per cent of the total gaseous volume during post pasteurisation conditioning.

When oxygen falls the process does not simply slow, it changes. Anaerobic pockets make sour smelling compounds and kill the thermophilic flora. DMR links olive green mould directly to lack of aeration during compost preparation, especially during Phase II, alongside temperatures above 60 degrees.

Distribution is measured with temperature, because temperature follows the air. DMR sets the limit in a Phase II tunnel plainly: the difference between air above the compost, the compost itself and the plenum below should not exceed 3 degrees Celsius.

Use a grid of probes and compare readings against each other rather than against a setpoint.

• Steam rising evenly across the surface, not from two spots.
• No cold zone near the walls or the door end.
• Probe spread inside the limit at every reading hour.
• No sour smell anywhere along the surface.

When the spread is wide, the cause is usually mechanical and cheap to fix. Look first at compaction from the loader, then at a dip in the surface, then at floor slots blocked by old compost, then at air escaping round a door seal instead of going through the mass.

Raising fan speed on a leaking or compacted system simply moves more air along the easy path and dries the surface. Change one thing, run one batch, record what the spread did. A bigger fan bought without this evidence usually solves nothing.

Filling and levelling comes first. The blower runs until compost, plenum and the air above sit at roughly one temperature, around 45 to 48 degrees Celsius, which takes about four to five hours.

Then pre pasteurisation conditioning holds the mass between 45 and 52 degrees for two days. Pasteurisation follows at 58 to 59 degrees for 4 to 6 hours. Last comes post pasteurisation conditioning at 45 to 48 degrees for 3 to 4 days, until ammonia is no longer detectable. Smaller tunnels often need 4 to 5 days to reach the same point.

DMR fills a bulk chamber to a height of 2 to 2.2 metres, loaded so one square metre of tunnel floor carries about 900 to 1000 kg of compost. An even fill at that loading is what lets one blower serve the whole mass.

A deeper fill on the same floor raises resistance and the bottom compacts under its own weight. A shallow patch becomes the easy path for air. Level the surface by hand after the loader has finished, and check the height at several points rather than one.

How fast you move between stages matters as much as where you stop. DMR narrows the dampers and lets the compost heat itself at roughly 1 degree Celsius per hour, reaching 58 to 59 degrees in about 10 to 12 hours. After the hold, temperature is brought down at about 1.5 degrees per hour into the conditioning band.

Throughout, the difference between air above the compost, the compost and the plenum should not exceed 3 degrees. A fast jump or a sudden drop shows the air is working on one part of the mass only.

Compost leaves Phase II on evidence, not on the calendar. DMR describes finished compost as dark brown and sweet smelling, holding 64 to 66 per cent moisture with no liquid oozing on a firm squeeze, and carrying free ammonia below 10 ppm.

Temperature is then brought down gradually to 25 to 30 degrees Celsius before spawning. Expect a further 20 to 25 per cent weight loss across Phase II. If ammonia is still detectable, conditioning continues; spawning into ammonia kills young mycelium and invites moulds that live on the amines left behind.

Compost arriving from Phase I carries fly eggs, mites, nematodes, and the spores of competitor moulds and weed fungi. A controlled heat treatment kills them. It is not meant to kill everything: the thermophilic fungi and bacteria that convert ammonia in the next stage have to survive, or the compost will never become selective.

That is the whole balance of the operation. Too little heat and the competitors ride into the growing room with the compost. Too much and you sterilise away the organisms that make Phase II work at all.

DMR is specific: compost is pasteurised properly when held at 58 to 59 degrees Celsius for 4 to 6 hours. The temperature is reached by narrowing the dampers and letting the mass heat itself at about 1 degree per hour, which takes roughly 10 to 12 hours.

The ceiling is firm. Above 60 degrees, DMR warns, all kinds of organisms are killed, including the thermophilic fungi essential for Phase II. The same manual lists temperature above 60 degrees during pasteurisation, together with poor aeration, as the trigger for olive green mould.

A hold is only real at the coldest point of the mass. Air temperature in the tunnel reaches the target long before the compost does, and a probe near the door reads differently from one in the middle.

DMR keeps the difference between air, compost and plenum within 3 degrees Celsius, which is itself a check on whether any single probe can be trusted.

• Probe the compost, never the air, for the hold.
• Both ends and the centre, at two depths.
• Start the clock on the coldest probe.
• Log every probe every hour through the hold.

Seasonal growers using long method compost often have no boiler. DMR publishes a chemical alternative applied at the last turning, after which the compost is heaped and covered with a polythene sheet for two days. Products and approvals change, so read the current label before using anything and never scale a published figure yourself.

DMR trial data on that treatment is useful context: 18.1 kg of mushrooms per 100 kg compost against 10.5 kg for a water sprayed control. Casing soil is a separate job, steamed at 60 to 65 degrees for 6 to 8 hours.

Phase II is not one event. Before the peak the whole mass is held at 45 to 52 °C for about two days. ICAR-DMR calls this pre-pasteurisation conditioning, or PPC. Its job is to grow the thermophilic flora, the heat loving bacteria and actinomycetes that later do the ammonia work.

After pasteurisation the compost is brought down at about 1.5 °C per hour and held at 45 to 48 °C. This is post-pasteurisation conditioning, or POPC. DMR gives 3 to 4 days for a bulk tunnel above 15 tonnes, and 4 to 5 days for a smaller one, or as long as the ammonia takes.

Compost leaving Phase I carries roughly 800 to 1,000 ppm of ammonia and sits at pH 8.2 to 8.5. That ammonia is nitrogen, and it is not thrown away. During conditioning the thermophilic community takes it up and locks it into microbial bodies, which the mushroom later digests. Some also leaves with the exhaust air.

Do not call this one single pathway. Uptake, chemistry and gas loss act together, in shares set by air supply, temperature and the nitrogen the formulation put in. A mix stacked above 1.75 percent nitrogen leaves more ammonia for these days to clear.

Conditioning is aerobic work. DMR asks for oxygen above 10 percent inside the compost mass throughout, and notes that demand during PPC can climb higher still. Starve the mass of air and the microbes that eat ammonia slow down while wet airless pockets form.

There is also a floor. Below 40 °C mesophilic fungi, the ordinary moulds of a warm room, move in and the compost becomes unsuitable for mushroom growth. Low and slow is not a safe way to stretch conditioning. If the mass is drifting down, correct the air circuit rather than add days.

The end point is a condition, not a date. DMR ends POPC when there is no detectable ammonia, which it places below 10 ppm. Collect that evidence at several points while the compost is still in the band, using a declared safe method, never by breathing tunnel air.

Read it with everything else: compost temperature steady in the band and not drifting, white actinomycete flecks through the whole mass rather than one layer, a sweet smell in place of a sharp one, and no wet airless pockets. If two of those disagree with the ammonia test, investigate before release.

Ammonia is nitrogen on the move. Urea, chicken manure, cotton seed cake and every other nitrogen source breaks down during Phase I, and the nitrogen leaves the material as ammonia. This is normal. DMR reports compost at the end of Phase I holding about 800 to 1,000 ppm, with pH pushed up to roughly 8.2 to 8.5.

The size of your ammonia problem is therefore decided long before the tunnel. DMR notes that a mix carrying more than 1.75 percent nitrogen loses more of it as ammonia, and that such compost attracts yellow moulds, ink caps and olive green mould.

DMR states plainly that we generally cannot smell ammonia below 10 ppm. Read that carefully. Your nose can tell you ammonia is present. It can never tell you the level is low enough. Those are different statements, and crops are lost on the difference.

A nose also tires. After a few minutes in the corridor you stop noticing a smell that has not changed. That is olfactory fatigue, and it makes the second sniff less reliable than the first. Never deliberately breathe compost air to test a batch. Ammonia is an irritant gas and a tunnel is a confined space.

When someone reports that the compost still smells of ammonia, do not reach for a chemical and do not add a day. Ask four questions first, because each one changes the answer.

Which stage is this: end of Phase I, mid conditioning or after cooling? What method produced the reading: an instrument, a detector tube or a nose? Where was the sample taken: front, back, top, middle or plenum? Has cooling started, since a warm mass releases ammonia that a cooled mass holds back? A reading without those four facts cannot support a spawning decision.

• Stage
• Method
• Sample location
• Cooling status

If ammonia is still there at spawning, the compost tells you within days. Spawn runs slowly or stops in patches. DMR lists ink caps, the black inky Coprinus mushrooms, under presence of ammonia and high nitrogen in compost. It ties Oedocephalum mould to ammonia and amines that were not eliminated during pasteurisation and conditioning.

By then nothing in that batch can be repaired, so the lesson belongs to the next one. Check the formulation nitrogen you actually stacked, the oxygen supply during conditioning, and whether your ammonia evidence was honest or convenient.

Air leaves the fan into the plenum, the sealed space under the floor. It passes up through the perforated air floor, through the compost, into the space above, and back to the mixing section where fresh, return and exhaust dampers decide what the fan sends round again.

Every part fails quietly. A blocked floor outlet leaves a dead zone no probe may sit in. A worn door seal pulls untreated air into a pasteurised batch. A choked plenum drain holds water that cools the air from below. Inspect all of them before you fill, because once compost is in you see none of it.

DMR fills a bulk chamber to 2 to 2.2 metres, loaded so that one square metre of floor carries roughly 900 to 1,000 kg of compost. Depth is the point. Air takes the easiest path, so a shallow patch or a wheel-compacted loader track pulls air away from the rest of the mass.

Once filled, the blower brings plenum, compost and the air above to one temperature, around 45 to 48 °C. DMR describes this levelling off as a job of four to five hours. Until it is done, no tunnel reading means much.

A tunnel has three temperatures: the air above the compost, the compost itself, and the plenum below. DMR says the difference should be as small as possible and must not exceed 3 °C. A wider gap means air is not passing evenly through the mass.

During peak heating the compost rises at roughly 1 °C per hour and holds at 58 to 59 °C for 4 to 6 hours. Above 60 °C the process turns: DMR warns this kills the thermophilic fungi Phase II depends on, and lists it as a trigger for olive green mould.

A fan rated in kilowatts tells you what the motor draws, not what air reaches the compost. Resistance rises with fill depth, with moisture and with any compaction, so the same fan delivers different airflow on different batches.

So judge the fan by the mass, not the label. Watch plenum pressure, watch how quickly the three temperatures converge, and watch whether the far end of the tunnel behaves like the near end. Advance a batch on verified compost condition, not because one air sensor touched a set point while the compost stayed cold.

Four facts travel with every value: where the sensor sits, when it was last checked against a reference, what unit it reports, and what the machinery was doing at that moment. Strip one away and the number becomes an opinion.

Fan state matters more than most operators expect. Compost temperature with the fan running, and the same probe ten minutes after it stopped, are not the same measurement. Write the process state beside the value every time, so the batch record can be read a month later by somebody who was not standing there.

A loaded tunnel varies in three directions. DMR fills to 2 to 2.2 metres, so the top of the mass and the layer near the floor differ, and the far end differs from the door end.

No Indian source publishes how many probes a tunnel needs. The count follows your geometry and the zones you know go wrong, so measure it on your farm rather than copy a number. Use the DMR rule that the spread must not exceed 3 °C to test whether your coverage is enough.

• Front and back
• Top, middle and bottom
• Zones with a bad history

Check probes against a known reference on a fixed day each month, and write the check down even when nothing has drifted. A probe that is never checked is one you will eventually argue with.

Four failures hide behind a tidy screen. A value that has not moved for hours is usually a dead channel, not a stable tunnel. A jump of several degrees in a minute is usually a loose connection. A wet or bent probe reads its own condition. A probe moved at unloading and never relabelled reports the wrong end forever.

When the air sensor shows 48 °C and the compost probe at the far end shows 43 °C, that gap is not a nuisance. It measures your air distribution, and it is the evidence DMR asks for when it limits the spread to 3 °C.

Do not average the two and move on, and do not quietly disable the awkward channel. Investigate the load, the floor and the dampers, write what you found, then decide. Nobody should certify compost from a screen in another room, because a screen cannot see a blocked floor outlet.

Somebody has to say that this batch may be spawned. That decision rests on four kinds of evidence: what you saw, what you measured, what the process record shows, and what a laboratory confirmed.

Any one of them alone will mislead you. Colour tells you about heat history but nothing about ammonia. A squeeze tells you roughly about water but nothing about pH. The batch curve tells you what the tunnel did but not what the compost became. Decide on the set, and write the name of whoever decided beside the batch number.

DMR describes compost after Phase II as holding 64 to 66 percent moisture, with no liquid oozing when it is squeezed firmly, and free ammonia below 10 ppm. The pH that suits Agaricus bisporus mycelium is 7.2 to 7.8, and compost is cooled to 25 to 30 °C before spawning.

Final nitrogen depends on the method used: DMR gives 1.75 to 2.0 percent for long method compost, 2.0 to 2.2 percent for short method, and 2.2 to 2.5 percent for indoor bunker compost. Judge your batch by the figure for the method you ran.

• Moisture
• Ammonia
• pH
• Nitrogen
• Temperature

Two DMR moisture figures circulate and growers mix them up. The manual says good synthetic long method compost should hold 68 to 72 percent moisture at spawning. The same manual describes compost after Phase II as 64 to 66 percent. Both are DMR figures and both are correct, because they describe different compost.

So name your compost before you name your target. Above 72 percent, DMR warns that aeration fails, conditions turn airless and plaster moulds appear. NHB links compost below 64 percent, with wet casing, to weeper mushrooms. Neither end is small.

The most damaging line in a release sheet is the one left silently blank. If you did not test pH this batch, write not tested. If the ammonia reading came from one point rather than three, write one point. A record that hides its gaps will be trusted more than it deserves.

Small units can run this with a printed checklist and an outside laboratory a few times a season. Larger plants need a named release role, batch trends, and a written rule for a batch that fails one check but passes the rest.

Two different jobs get called sampling. One asks whether the batch may be released. The other asks why one corner behaves badly. They are not taken the same way.

For a release question you want a composite, a single mixed sample built from equal amounts taken all over the load, because you want the batch average. For a diagnosis you want the suspect zone kept separate and labelled, because the whole point is the difference. Mix a bad zone into the composite and it disappears into an average that looks acceptable while the crop fails.

DMR fills a bulk tunnel to 2 to 2.2 metres, so depth alone creates three different environments, and the far end rarely matches the door end. Take from front, middle and back, at top, middle and bottom, before calling a sample representative.

Timing matters as much as position. Moisture and ammonia both change while the mass is cooling, so a sample taken at noon and one taken at midnight answer different questions. Fix the stage at which you sample, write it down, and keep it the same for every batch so the numbers can be compared.

Build a composite properly. Take an equal amount from every chosen point, empty them into one clean container, mix by hand with a clean tool, then reduce the pile by quartering until you have the quantity the method needs.

Three habits ruin it. A larger scoop from the easy points weights the result toward them. The loader bucket adds whatever it carried last. A sample left open while you finish the round loses the very moisture you are testing. Keep any suspect zone out of the composite and send it as its own labelled sample.

A sample without a label is compost in a bag. Write batch number, point, depth, date, time, stage and compost temperature on the container, not only in a notebook, and seal it at once.

Record what you asked the laboratory for and by which method, because a pH figure depends on the water ratio and the procedure. When the result returns, file it against the same batch number as the process curve. A result that cannot be traced to a batch, a point and a stage teaches you nothing for the next fill.

Take a heap that will not heat. DMR reports that below 1.5 percent nitrogen the material is not properly fermented and the heap may not pass 55 to 60 °C, and it sets a minimum base batch of 300 kg because small heaps lose heat too fast. The heap may also be too wet and airless, or genuinely too dry.

Each of those causes predicts something else you can check. Low nitrogen means the formulation record will show it. Too wet means leachate at the base and a sour smell. Too small means the outside is cool but the very core is warm. Go and look for what you should not find.

• Nitrogen too low
• Too wet and airless
• Batch too small
• Too dry

Several Indian figures act as boundaries, and crossing one points at a domain. Compost above 72 percent moisture cannot aerate properly, turns airless and invites brown and white plaster moulds. NHB links compost below 64 percent, under wet casing, to weeper mushrooms.

Outside pH 7.2 to 7.8 the mycelium slows and white plaster mould may invade. Above 60 °C at pasteurisation DMR warns that the useful thermophilic fungi die and olive green mould follows. Ink caps and Oedocephalum point back at ammonia and nitrogen. The symptom does not prove the cause, but it tells you which measurement to take next.

Compost problems are process problems. No spray corrects moisture, pH, nitrogen or air distribution, and anything applied on a mushroom farm must be checked against its current label approval and state rules before use, not chosen from an old note book.

So the next step after a diagnosis is a measurement, not a chemical. Change one thing in the limiting domain, record what you changed and why, then look for the response in the same measurement. If the response does not come, your cause was wrong and the record you kept is what lets you say so.

Draw your unit as a line. Raw straw and manure storage sits at the dirty end, then the Phase I yard, transfer, the Phase II tunnel, ready compost and spawning. Spent compost from the cropping rooms sits outside that line, because it is the dirtiest material on the farm.

Work should move along that line and never back up it. The same rule covers people. A worker clearing spent beds should not enter the ready compost bay in the same boots, and a visitor from the cropping room should not be shown the tunnel.

Contamination rarely arrives by air. It arrives by traffic, and a few habits cause most of it.

One loader doing every job, from spent heaps in the morning to ready compost in the afternoon. Forks shared between the Phase I yard and the tunnel floor. A drain running from the spent heap across the yard where straw is stacked. Spent compost parked beside ready compost because the space was free. Each is cheap to fix: a route, a second tool, a written order of work.

• Shared loader
• Shared tools
• Drainage across clean ground
• Spent compost stored close by

Indian practice does use disinfectants and fumigants around compost and casing, and this course will not print a dose for any of them. Approvals, concentrations and permitted uses change, so check the current label approval and your state rules before anything is mixed, and use the protective equipment the label demands.

The reason to be careful is on the farm already. Wet bubble spores survive in casing soil for about three years, so a soil route that crosses a compost route can carry a problem for seasons. Cleaning counts only when somebody checks it and signs that it was done.

A batch record is not a temperature chart. It holds five things: the identity of the batch, the inputs that went into it, the process it passed through, every deviation from plan, and the decisions people took.

Each entry carries the same fields, and the last two are the ones farms skip. Stage. Measurement, with its point. Equipment state, meaning what the fan and dampers were doing. The deviation. The action. The reason for it. And the result, written later when you went back and looked. A record with actions but no results teaches nobody anything.

Write down the lots, not the recipe. Which straw, from which supplier, how many bales and how old. Which manure, from where, arriving when. The weights you actually put on the heap, including the substitution you made when the cotton seed cake did not arrive.

Mass tells the truth later. DMR reports that a tonne of straw yields about 1.75 to 2.0 tonnes of long method compost, 2.0 to 2.5 by short method and 3.0 to 3.5 by indoor bunker. If your ratio drifts far from the method you ran, either the water or the record is wrong.

Log the states a decision hangs on rather than everything a controller can print. The fill, in tonnes and kilograms per square metre, since DMR works to 900 to 1,000 kg. The levelling off at 45 to 48 °C. The peak at 58 to 59 °C and the hours held there. The conditioning hold, the days it ran, and the ammonia evidence that ended it.

Beside each, write the fan and damper state and the initials of the person on shift. Two identical curves with different people and weather are not the same batch.

• Fill
• Levelling
• Peak
• Conditioning
• Release

The batch number should not die at spawning. It belongs on the room sheet, the spawn lot and the yield record, because that is the only way a third flush problem traces back to a formulation change six weeks earlier.

Paper is fine for a small unit if it is complete and legible and kept where the next shift can read it. What matters is that the record was written while the work happened. A record filled in from memory on Sunday evening is a story, and stories cannot be investigated.