Farm Fresh Gourmet Specialty Mushrooms

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8987 E Tanque Verde, Ste., 309-300

Tucson, AZ 85749

SMS: Spent Mushroom Substrate


What is SMS?


SMS stands for Spent Mushroom Substrate and is made up of composted organic material that is left over after a mushroom harvest. Typically these SMS bags are used for multiple mushroom harvests but once they start slowing down in mushroom production, it is time to retire the substrate bag and start fresh. However, even once the SMS bags stop producing a harvestable amount of fruits they can still be used for many other purposes in agriculture from animal feed to soil additions. SMS is extremely high in organic materials and important nutrients such as Calcium, Potassium, and Magnesium and can provide an extra boost to your gardening!


The particle size of SMS can vary depending on the substrate used and how it was processed however a general rule of thumb would be that smaller SMS particles are better for applications like sports fields, lawns, golf courses, and general turf applications. If the particles are too large when being applied to a surface that is meant to be even and smooth, this can cause problems and unevenness later down the line. However, this does not mean that SMS cannot be used if it is made up of larger particles. All this means is that the SMS with larger particles needs to be used in other applications such as soil amendments.


When it comes to SMS, there should be a specific, earthy odor about it; it will not be odorless but it should not smell bad. If your SMS smells rotten or ammonia-like, you should not use it for any sort of gardening purposes. This type of smell is an indicator that the SMS is not fully mature and not ready to be used for any sort of agricultural purpose, if you use immature SMS for agricultural purposes it can be detrimental and give the opposite effect desired.


SMS that is ready to be used for non-mushroom related purposes should sit in a happy moisture medium of between 30 and 50% moisture. Obviously after having been in a mushroom growing environment for such a long time, the SMS will have a high moisture content however any SMS with a moisture content of higher than 60% may be more trouble than it’s worth. SMS that is too wet is heavy, difficult to work with, and clumps very easily, making it difficult to spread out effectively. The test that the Penn State agricultural department suggests using to determine if the SMS is ready to use is to take a handful and squeeze; if a noticeable amount of water comes out, the SMS is probably too wet for use and needs to be dried more.


As mentioned above SMS contains a fair amount of organic matter, sitting between 40 and 60% organic matter for most SMS bags. Despite having such a significant amount of organic matter however, if you are planning on using SMS for gardening, keep in mind that SMS does not typically contain much, if any usable Nitrogen. So, if you are gardening in a place that does not have much Nitrogen in the soil, do not rely on SMS to provide that for your plants and instead add another type of soil addition on top of the SMS.


The pH of SMS should typically sit between 6 and 8; Sonoran Mushroom Company’s SMS bags sit around 7. You typically want to stay within this range for most gardening because while there are a select amount of crops that are fond of more acidic environments like blueberries or more basic environments such as asparagus most plants sit happily around 7. Though that’s not to say that if the SMS is slightly off that range that it is dangerous for the crop. The pH of SMS only gets concerning when it is either above 8.5 or below 5.5.


What are some commercial uses for SMS?


Topper for Newly Seeded Lawns: Some of the concerns that come after seeding lawns include birds and other animals eating the seeds and keeping enough water content in the area so that the seeds can germinate. When spreading SMS over newly seeded lawns, not only does it provide cover from birds and other animals but it also creates a humid environment that will retain water in and around the seeds so they can happily germinate. Due to the fact that there is a nearly unlimited supply of SMS right now, it seems silly that it is not currently being used for this in projects both large and small.


Soil Amendment: Adding SMS to your garden can be a wonderful addition for soils that are poor in organic material and soils that have problems retaining water.


Bioremediation: This one is less of a “backyard gardener” application but still pretty cool nonetheless! Scientists have been researching the possibilities of using SMS for bioremediation (or using microorganisms to clean up a polluted site) by introducing the active enzymes and fungi that are active in SMS to consume and remove pollutants. So, while this may not be something that is immediately relevant in your life it could be a fun experiment to do if you have time by placing SMS in an area that has been affected by pollution in your community and see what happens!


Animal Feed: If you raise horses, cows, or any other type of farm animal, SMS can be a fantastic addition to the typical feed you give them. Research has shown that the active nutrients and enzymes in SMS can increase the nutritional value of food by acting as anti-inflammatories and antioxidants for the animals. The enzymes found in SMS may also be able to prevent certain diseases in the animals and consequently the humans who care for them.


Energy Feedstock: Finally, SMS has been recently being researched as a potential alternative energy source. The exact details of this are still in the beginning steps of development but there is a potential that this SMS, this mushroom waste could potentially be used in the future for alternative forms of energy.


If you would like some SMS to try some of these at home applications, just go to Facebook, like Sonoran Mushroom Company’s page and join the Sonoran Grower’s Guild. Members of this group get access to free SMS, training, classes, meetups with local growers, contests, tours, mycology expert advice, and more!


Author: Chelsea Hoel