MushroomFarming / guide

Casing for Button Mushroom

Understand casing by function, physical properties, preparation, hygiene and uniform application.

Practical explanation + detailed referenceSources & review ↓

Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.Pavimps · CC BY-SA 4.0View full photograph ↗

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Understand the topic

What you need to know.

Casing is the soil layer spread over colonised compost, and it is where every button mushroom forms. This page covers what the layer does, which materials work in India, how to treat it so it does not bring disease in, how to lay it evenly, and how to read the week after casing before you change the room.

Teaching revised 2026-09-24. Source-linked editorial synthesis; this date does not imply independent technical review.

Part 01

What casing does, and what it does not

Button mushrooms do not fruit on bare compost. ICAR-DMR describes casing, a thin layer of soil laid on top of spawn-run compost, as a prerequisite for fruiting.

The layer does four jobs. It holds a reserve of water the crop draws on. It lets carbon dioxide escape from the compost below. It supports the growing mushrooms. And it is where the switch from spreading mycelium to pinheads happens.

What casing does not do is feed the crop. The manual lists being deficient in available carbon and nitrogen as a required property. The food is in the compost; a nutrient-rich layer invites moulds rather than mushrooms. So a farm can have good compost and still lose a crop to casing that is too dry, too wet or carrying disease.

Source: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption

A dense flush of white button mushrooms fruiting from a compost bag with casing-soil specks, photographed in Assam, India. — A flush on a compost bag in Assam. The mushrooms stand in the casing layer, not in the compost beneath it. Photo: Medhi jyoti, CC BY 4.0. Source

Part 02

The figures ICAR-DMR gives for the layer

These are the published values for casing itself. The manual gives two thicknesses: it defines casing as a 3 to 4 cm layer, then instructs applying 4 to 5 cm. Choose one, record it, and keep it the same on every bed.

Thickness3 to 4 cmThe same manual instructs 4 to 5 cm at application.

pH7.0 to 7.5Neutral.

Conductivity400 to 600 micromhoLow salt content.

Wetting before treatment50 to 60 % of water holding capacity

Casing moisture at pinningabout 50 %Stated as 50 plus or minus 2 percent.

Source: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption

Part 03

Casing materials that work in India

Peat is the world standard but is not available in India, so ICAR-DMR lists local alternatives. Whatever you choose, judge it by its properties: soft, light, porous, able to hold a lot of water, and poor in food for the fungus.

Well decomposed farmyard manure, preferably two years old.
Spent mushroom compost decomposed for two years.
Composted coir pith that is well decomposed and water leached.
Mixtures of farmyard manure, spent compost and coir pith in the proportions the manual lists.
Burnt rice husk with decomposed farmyard manure, used for seasonal button growing in Haryana and Punjab.
The ICAR-DMR button folder's mix: two-year-old cow dung manure and loam soil in equal parts.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · ICAR-DMR button folder

Part 04

Treat casing, because it carries disease in

Wet bubble spreads through casing soil. The ICAR-DMR wet bubble folder reports that its spores survive in casing soil for up to three years, so soil carried over from an old crop, or garden soil, is a standing risk.

Wet the material to 50 to 60 percent of its water holding capacity first, because dry soil does not carry heat through the heap. The manual then steam pasteurises it at 60 to 65 °C for 6 to 8 hours and lets it cool. The wet bubble folder gives a shorter treatment of 54.4 °C for 15 minutes. The two come from different ICAR-DMR documents; follow one and record which.

Chemical treatment of casing is also documented. Doses are not given on this page: check current label approval for use on mushrooms first. Store treated casing in clean bags or a clean room so it is not infected again before use.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · ICAR-DMR wet bubble folder

Steam treatment of casing, as the ICAR-DMR manual sets it out

HeapMake a heap of the casing material on a clean surface.
WetBring it to 50 to 60 percent of its water holding capacity.
SteamFill trays into a pasteurisation chamber and hold at 60 to 65 °C for 6 to 8 hours.
Cool and storeLet it cool on its own, then keep it in clean bags or a clean room until casing day.

Part 05

Prepare ahead, then lay the layer evenly

Evenness matters more than the exact figure. A thin patch dries first and pins early, a thick patch pins late, and the bed ends up carrying two flushes at once.

Prepare in advanceThe ICAR-DMR button folder finishes casing preparation about 15 days before casing, which means starting right after spawning.
Keep the clumpsDo not sieve the casing. The manual uses it as it comes, with clumps, because they leave more air spaces in the layer.
Level the compost, then caseOpen the spawn-run bag, even the compost surface with gentle hand pressure, give it a light spray, then spread the casing using iron rings of 4 cm height or wooden blocks as depth guides.
Leave small mounds and valleysThe top of the layer should not be flat. Its small mounds and valleys matter later, because the valleys are where you look for mycelium at the end of case run.
Water in instalmentsSpray water in a few instalments so that it does not run through into the spawn-run compost, and record every watering.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · ICAR-DMR button folder

Part 06

The week after casing: case run

Case run is the week in which mycelium grows up from the compost into the casing. ICAR-DMR runs it at 24 plus or minus 1 °C, 95 percent relative humidity and carbon dioxide above 7500 ppm, with no fresh air, for about one week. The settings depend on the strain.

Case run is complete when mycelium shows in the valleys of the casing across the bed. The room is then changed: air down to 15 to 17 °C, humidity to 85 percent and carbon dioxide to 800 to 1000 ppm by opening fresh air ventilation. Pinheads form 3 to 4 days after that change and reach button size in another 3 to 4 days.

The manual also warns that temperatures above 26 to 27 °C after casing should be avoided, so a warm week is a problem to fix, not to wait out.

Source: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption

White button mushrooms on casing soil in long shelf beds inside a commercial cropping room near Eger, Hungary. — Shelf beds on casing in a grow room, photographed at cropping. During case run the same surface shows only white mycelium in the valleys. Photo: Andrew Bossi, CC BY-SA 2.5. Source

Part 07

Mistakes that cost the first flush

Common mistakeReusing old casing or garden soil without treatment.

Do this insteadTreat every batch. Wet bubble spores survive in casing soil for up to three years.

Common mistakePasteurising casing while it is dry.

Do this insteadWet it to 50 to 60 percent of its water holding capacity first so the heat reaches the middle.

Common mistakeSieving the casing fine and pressing it flat.

Do this insteadUse it with its clumps and leave small mounds and valleys on top.

Common mistakeFlooding the new layer in one go.

Do this insteadWater in a few instalments so that nothing runs into the compost.

Common mistakeChanging the room on a calendar date.

Do this insteadChange it when mycelium shows in the casing valleys across the bed.

Sources: ICAR-Directorate of Mushroom Research: Mushroom Cultivation, Marketing and Consumption · ICAR-DMR wet bubble folder

Go deeper

Technical reference, records and tools.

Detailed crop-stage information, parameters, diagrams and specialist tools are kept together below. This material retains its source conditions and review limits.

Open the complete technical reference

Button Mushroom · material

Casing for Button Mushroom

Agaricus bisporus

Understand casing by function, physical properties, preparation, hygiene and uniform application.

Publication: Public editorial page
External review: Not yet recorded · needed from Button Mushroom technical reviewer
Updated: 2026-08-22
Evidence records: 3

A few button mushrooms and pinheads emerging from black casing soil in compost bags, Tamil Nadu (uploaded by a TNAU student); dim and slightly soft. — Button mushrooms on casing soil in compost bags. Photo: Pavimps, CC BY-SA 4.0. Source

Button mushroom crop cycle

CompostDay 0Pasteurised, ammonia below 10 ppm
Spawn run12-14 daysAir 23 ± 1 °C, RH 95%
CasingDay 153-4 cm layer, pH 7-7.5
Case runAbout a weekMycelium reaches the casing valleys
Pinning3-4 daysAir to 15-17 °C, RH 85%, fresh air in
FlushesFlush by flushAir 15-17 °C, RH 80-85%

Picture → explanation → field task

A crop-room round

AI-generated educational illustrations. Not actual farm photographs, diagnostic evidence or construction specifications.

Generated illustration of gentle water application to a bare casing surface before mushrooms emerge.

Assess casing before watering

This scene shows casing without developing fruit bodies. Water needs depend on stage and material condition. The picture does not specify a quantity or a universal watering schedule.

Try this on your farm

Check the approved crop protocol and the actual casing condition before deciding how much to apply. Record the application.

Generated illustration of a grower recording different pin densities along mushroom beds.

Compare the pinning pattern

The bed does not develop uniformly at every position. Differences can involve inputs, water or room conditions. A patch is an observation, not a diagnosis.

Try this on your farm

Compare fixed locations over successive rounds. Photograph the same patch and record nearby readings before changing settings.

Stage10

Crop-stage dashboard

Casing

Biological state: A prepared surface layer is applied over colonised compost
Operator objective: Build a uniform functional interface for fruiting
Handoff: Enter case run with the layer protected

ObserveDepthstructuremoisturecleanliness

Depends onSpawn-run readinessprepared casinguniform application

Quick orientation

Casing is a functional crop layer, not merely a cover. Its structure, water-holding behaviour, sanitation, depth and interaction with the colonised compost shape the fruiting surface.

System role

Casing creates the crop-surface environment used through case run, pinning and cropping.

What to observe

Build a record before making a change.

Material identity and consistency
Structure and moisture through depth
Application uniformity
Clean handling

Decision framework

Use the observation to narrow a decision, then verify the response.

Select by verified properties
Prepare and record the blend
Apply uniformly
Protect structure during watering

Dependencies and handoffs

This topic cannot be interpreted in isolation.

Colonised compost
Casing quality
Water quality
Application method
Room hygiene

Practical layer

Start in the room with material identity and consistency and structure and moisture through depth. Record location, stage and recent events before changing the process.

Technical layer

The technical model joins colonised compost, casing quality, water quality. Any operating value must be attached to a registered parameter, measurement location and applicable condition.

Evidence boundary

This page is grounded in: Physicochemical characterization of casing materials used in Button Mushroom cultivation; Mushroom Cultivation, Marketing and Consumption; Technical and diagnostic services. Source provenance does not remove the need to check stage, system, date and local applicability.

Progressive depth

Go deeper without losing the field question.

PracticalWhat to notice in the room

Material identity and consistency
Structure and moisture through depth
Application uniformity
Clean handling

TechnicalHow the interacting system is interpreted

Colonised compost
Casing quality
Water quality
Application method
Room hygiene

ResearchWhich evidence records govern this page

ICAR-MR-CASING-2025
ICAR-DMR-CULTIVATION-MANUAL
ICAR-DMR-SERVICES

Technical registry

The numbers for this stage, with their source.

Values are published from ICAR-DMR guidance with the stage and measuring point they apply to. A parameter still marked pending has no published Indian value yet.

BUTTON.CASING.MOISTURE_STATUS

Casing moisture at pinning

48 to 52 % moisture

ICAR-DMR gives 48 to 52 percent casing moisture at pinning; the layer itself is 3 to 4 cm deep.

Stage: Casing and case run
Measured at: Representative depth through the casing layer
Crop meaning: Water availability at the crop surface when pins form.
Applicable conditions: Casing material; Depth; Sampling method

published sourced

BUTTON.CASING.PH

Casing pH

7 to 7.5 pH

Prepared casing should read pH 7.0 to 7.5 with electrical conductivity of 400 to 600 micromho.

Stage: Casing preparation
Measured at: Prepared casing composite sample
Crop meaning: One material-quality characteristic among several physical and biological properties.
Applicable conditions: Material blend; Test method; Sanitation process

published sourced

Evidence and review record3 mapped sources

Sources support the page architecture and conceptual guidance. Technical values remain governed separately in the Button registry.

Tier C · research

Physicochemical characterization of casing materials used in Button Mushroom cultivation

Casing function and material-characterization context. Trial findings remain bounded to the study design.

Accessed: 2026-08-22
Publisher: Mushroom Research, ICAR

Open original source

Tier A · foundational

Mushroom Cultivation, Marketing and Consumption

Broad cultivation, post-harvest and market context. Values are not promoted without page-level review.

Accessed: 2026-08-22
Publisher: ICAR-Directorate of Mushroom Research

Open original source

Tier A · institutional

Technical and diagnostic services

Official scope for compost and casing tests, crop protection diagnosis, farm design and crop-management support.

Accessed: 2026-08-22
Publisher: ICAR-Directorate of Mushroom Research

Open original source

Read the evidence

Sources & review.

Editorial update: 2026-08-22. Independent technical review is not recorded for this entry.

Physicochemical characterization of casing materials used in Button Mushroom cultivation ↗
Mushroom Research, ICAR · 2025
Mushroom Cultivation, Marketing and Consumption ↗
ICAR-Directorate of Mushroom Research
Technical and diagnostic services ↗
ICAR-Directorate of Mushroom Research

Reading a source is not the same as applying its instructions to every farm. Confirm species, strain, crop stage, system, region and publication date. Old chemical recommendations are not current-use instructions.

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