About Substrate Mixers
Typically mushroom farmers use substrate mixers when they add desired amendments to the substrate they intend to use or when they are using a combination of substrate materials. The mixer insures that the substrate is uniform, so that the mushrooms can get the sustenance they need throughout the grow bag, bottle or tray.
Substrate mixers may also be used to uniformly mix spawn with the substrate if the substrate is not sterilized.
Sterilized substrates in bags are normally inoculated with spawn in a clean atmosphere. Then the bags are sealed to keep out contaminants. The spawn is then mixed into the substrate by agitation. It is simply too difficult to sterilize a mixer, keep the substrate sterile while mixing, then get the substrate into bags without introducing undesirable microorganisms in the process.