Subject:  Spent Mushroom Compost

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> I am producing mushroom compost in Turkey. I am looking for =
information on usage of spent mushroom compost as a fertilizing agent in =
gardening, etc... I would appriciate any help/info abt. this subject. =
Could you recommend me some literature on how to treat spent compost =
before supplying to the end-user? Is mushroom compost too salty for this =
kind of use? Should it be enriched with other chemical fertilizer to =
have the right effect?
>=20


Greetings Cenk,

Mushroom compost is widely used as a soil amendment, but it is not =
usually called a fertilizer.  A fertilizer here in the United States =
must typically have a uniform percentage of nitrogen, phosphorous, and
potassium (NPK) such that every batch is uniform and the same as =
previous and future batches.  Compost materials rarely meet that strict =
standard of uniformity.  In some areas of the United States, a product =
must also have a minimum of 1% of each ingredient of NPK and that the =
guaranteed analysis must be clearly stated on the label or when the =
product is sold.

Most compost products are used more for their soil amending values first =
and their fertilizer values second.  Organic matter helps the soil hold =
moisture, enhances the development of beneficial soil organisms,
provides needed air, and feeds earthworms who aerate and vitalize the =
soil.  Compost products are typically considered to be too valuable to =
use on farmland and are sold to wholesale and retail markets where they
are used in horticultural mixes, nursery planter soils, landscaping, and =
gardening.  Mushroom compost is sold extensively in these markets.

If the compost is high in salts, which can only be determined by a soil =
analysis, then it should be sold in applications where it will be tilled =
into a soil that will be watered heavily or flushed to reduce salt
concentrations.  In containers, these salts can have an inhibiting =
effect on plant growth.  Very few mushroom compost products I have =
worked with, however, have had a high salt concentration.

Mushroom compost can be utilized as a fertilizer, however, even if it =
may be difficult under our legal system to call it one.  Let us assume =
that the compost has 1% nitrogen.  This equates to 10 kilos of N per =
tonne.  If the nitrogen demand of a crop calls for 50 kilos of N per =
acre, then 5 tonnes of compost would seemingly supply the need for N.  =
Only 40% of the N in compost, however, is available the first year. This =
means that you would have to apply closer to 12 tonnes of compost per =
acre to supply the annual demand for N.

An advantage in using compost, however, is that 20% of the N is =
available the second year, 10% the third, 5% the fourth, and so forth. =
This means that if you applied only 8-10 tonnes of compost the second =
year, it would have the same effect as the 10-12 tonnes the first.  As =
the years go on, this "accumulated fertility" will increase until the =
amount of organic matter applied to the soil each year could drop down =
to 5 tonnes per acre to supply the soil's nitrogen need.=20

This increasing organic matter loading will enventually increse the =
tilth and texture of the soil producing "unknown growth factors" and =
other benefits in the soil such as disease resistance, erosion =
prevention and pest deterrence that can not be supplied by chemical =
fertilizers alone.

Good luck!

Jim~ McNelly                 Compost@cloudnet.com
NaturTech Composting Systems, Inc.   320-253-6255=20
Information on Composting and Sustainable Futures
The Humusphere           HTTP://www.composter.com