Spent mushroom compost
Encyclopedia
Spent mushroom compost is the residual compost
waste generated by the mushroom production industry. It is readily available (bagged, at nursery suppliers), and its formulation generally consists of a combination of wheat
straw, dried blood, horse manure and ground chalk, composted together. It is an excellent source of humus, although much of its nitrogen
content will have been used up by the composting and growing mushrooms. It remains, however, a good source of general nutrients (0.7% N
, 0.3% P
, 0.3% K
plus a full range of trace element
s), as well as a useful soil conditioner
. However, due to its chalk
content, it may be alkaline, and should not be used on acid-loving plants, nor should it be applied too frequently, as it will overly raise the soil's pH
levels.
Mushroom compost may also contain pesticide
residues, particularly organochloride
s used against the fungus gnat
. If the compost pile was stored outside, it may contain grubs or other insects attracted to decaying matter. Chemicals may also have been used to treat the straw, and also to sterilize the compost. Therefore, the organic gardener must be careful regarding the sourcing of mushroom compost; if in doubt, samples can be analyzed for contamination – in the UK
, the Department for Environment, Food and Rural Affairs
is able to advise regarding this issue.
Commercially available 'spent' mushroom compost is not always truly spent. It is sold by mushroom farms when it is no longer producing commercially viable yields of mushrooms. It can be used to grow further smaller crops of mushrooms before final use on the garden.
Compost
Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...
waste generated by the mushroom production industry. It is readily available (bagged, at nursery suppliers), and its formulation generally consists of a combination of wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
straw, dried blood, horse manure and ground chalk, composted together. It is an excellent source of humus, although much of its nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
content will have been used up by the composting and growing mushrooms. It remains, however, a good source of general nutrients (0.7% N
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, 0.3% P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, 0.3% K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
plus a full range of trace element
Trace element
In analytical chemistry, a trace element is an element in a sample that has an average concentration of less than 100 parts per million measured in atomic count, or less than 100 micrograms per gram....
s), as well as a useful soil conditioner
Soil conditioner
A soil conditioner, also called a soil amendment, is a material added to soil to improve plant growth and health. A conditioner or a combination of conditioners corrects the soil's deficiencies in structure and-or nutrients.-Purpose:...
. However, due to its chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
content, it may be alkaline, and should not be used on acid-loving plants, nor should it be applied too frequently, as it will overly raise the soil's pH
Soil pH
The soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
levels.
Mushroom compost may also contain pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
residues, particularly organochloride
Organochloride
An organochloride, organochlorine, chlorocarbon, chlorinated hydrocarbon, or chlorinated solvent is an organic compound containing at least one covalently bonded chlorine atom. Their wide structural variety and divergent chemical properties lead to a broad range of applications...
s used against the fungus gnat
Fungus gnat
Fungus gnats are small, dark, short-lived flies, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae and Mycetophilidae , sometimes placed in the superfamily Mycetophiloidea, whose larvae feed on plant roots or fungi and aid in the decomposition of organic matter...
. If the compost pile was stored outside, it may contain grubs or other insects attracted to decaying matter. Chemicals may also have been used to treat the straw, and also to sterilize the compost. Therefore, the organic gardener must be careful regarding the sourcing of mushroom compost; if in doubt, samples can be analyzed for contamination – in the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, the Department for Environment, Food and Rural Affairs
Department for Environment, Food and Rural Affairs
The Department for Environment, Food and Rural Affairs is the government department responsible for environmental protection, food production and standards, agriculture, fisheries and rural communities in the United Kingdom...
is able to advise regarding this issue.
Commercially available 'spent' mushroom compost is not always truly spent. It is sold by mushroom farms when it is no longer producing commercially viable yields of mushrooms. It can be used to grow further smaller crops of mushrooms before final use on the garden.