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Additives & Chemicals
Calcium Nitrate (100g)
A soluble 15.5-0-0 calcium nitrate: a calcium and nitrogen supplement for compost-grown mushrooms like button and portobello, and for the casing layer that goes on top.
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Sold for cultivation and lab use. Keep away from heat and combustible material.
Dissolves fully in water, no residue left in the mix
Supplies both calcium and nitrate nitrogen
An oxidiser and an irritant, keep off skin and away from heat
The short version
Calcium nitrate gives fast nitrate nitrogen and calcium in one soluble feed. In mushroom growing it belongs with the compost-loving species — button, cremini and portobello (Agaricus) — where it adds nitrogen to the compost as it is built and calcium to the casing layer.
It is graded 15.5-0-0 with about 19% calcium, supplied as dry, fully soluble granules. It is not for grain spawn or sterilised bulk substrate, where added soluble nitrogen simply feeds contamination.
What it is
A soluble calcium and nitrogen feed
This is standard 15.5-0-0 calcium nitrate: 15.5% nitrogen, mostly fast-acting nitrate, plus about 19% calcium. It is a dry, free-flowing granular product that dissolves fully in water and is supplied ready to use.
How to use it in mushroom growing
For compost-grown mushrooms and casing
Its place is with the compost-loving mushrooms grown on composted substrate, the Agaricus group: button, cremini and portobello. It is not part of the grain or sterile-substrate side of the hobby.
Into the compost
When you build and wet a mushroom compost, calcium nitrate adds soluble nitrogen to feed the composting and calcium to firm up the structure. Dissolve it in the water you are adding, or scatter and mix it through evenly so it is not left in pockets.
Into the casing
A small amount worked into the casing layer adds calcium, which supports firm, even pinning. Gypsum or chalk are the usual casing calcium sources; calcium nitrate also brings a little nitrogen with it.
Go light
It is concentrated, so use a modest amount and adjust to your recipe. Dissolve it fresh rather than storing made-up solution.
Where not to use it
Not for grain or sterile bulk
Do not add it to grain spawn or to sterilised bulk substrate such as sawdust, coir or straw bags. Soluble nitrate sitting on a sterile, nutritious medium feeds bacteria and mould before your mycelium can use it, which invites contamination. On those, calcium comes from gypsum and any extra nitrogen from bran-type supplements, not from a soluble salt.
Storage
Keep it sealed and dry
It is hygroscopic, so it draws moisture from the air and will clump if left open. Store it sealed in a dry place, away from children and pets.
Common questions
Frequently asked
On compost-grown types (button, cremini, portobello) it feeds the compost with nitrogen during composting and adds calcium, which supports firmer mushrooms and more even pinning when worked into the casing.
Dissolve it in the water you add when building your compost, or mix a small amount evenly into the casing layer. It is concentrated, so use a light hand and mix it fresh.
It is a standard horticultural fertiliser, not hazardous in normal handling. Wear gloves if your skin is sensitive, wash your hands after, and keep it off food. It is an oxidiser, so store it away from fuels and anything flammable, and out of reach of children and pets.
The compost-loving Agaricus group such as button, cremini and portobello. It is not used on the grain or sterile-substrate side of the hobby.
No. Soluble nitrate sitting on grain or sterilised sawdust, coir or straw feeds bacteria and mould before your mycelium can use it. Keep it to compost and casing.
Sealed and dry. It draws in moisture and clumps if left open.
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Sold for legal gourmet mushroom cultivation and laboratory use. An oxidiser and irritant: handle and store with care and keep away from children.
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