Spent Mushroom substrate or compost is a good by- product of the mushroom production cycle. Most mushroom compost depending on their source may vary in their make up.
They have basic ingredients like; sawdust, horse blood, rice or wheat bran, chalk, quicklime, corn husk and other organic materials running through their formulation process which makes them excellent soil conditioners that do not leave any residues on crops like their counterpart conventional fertilizers.
However, the composting process, method of sterilization used or kind of treatment given to the potential compost ingredient are determinants in the levels of alkalinity and or salinity present in the finished compost product.
Compost is considered “spent” when one full crop of mushroom, has been taken or when further extension of cropping becomes unprofitable. The diversified uses of spent mushroom substrate in managing agriculture,environment and recycling energy have recently become an issue of concern and because of this, some choose to call it “used mushroom substrate”instead of just spent mushroom substrate.
Uses of Spent Mushroom Substrate
It is useful for conditioning compacted heavy clay soils. When mixed with such soils, the spent mushroom compost aerates the soil giving it a crumbly texture which is easier to work with.
It could also serve as good mulching material.When spread around the plant or liberally over the soil surface it helps to:
- Reduce weed growth
- Retain moisture
- Maintains the soil and increase nutrients
- The substrate incorporation @ 100,200 and 400 tons (fresh weight)/acre in nutrient poor soils like silty dry loam shows positive effect on the silage and grain yield of cash crops.
- The use of anaerobically fermented spent mushroom substrate as casing material gave mushroom yield at par with that of the peat based casing material with additional advantage of less bacterial blotch infection.
- Bio remediation of contaminated soils.
Used mushroom compost is low in soluble nitrogen, which means little risk of plant burn. The nitrogen is present in such a form that is released over time with decomposition. This means continuous supply until decomposition is complete.
Phosphate, Potassium, Calcium and Magnesium levels are high and salinity is generally below levels found in conventional manures. Micro elements such as; Copper, Zinc, Manganese, Iron, and traces of Boron are also present in good quantities.
The gardener should be mindful of his source of spent compost material since the quality can affect his soil properties. Because of their alkalinity,used mushroom compost should not be used on acid loving plants.
Used mushroom compost is best applied before planting to boost fertility and put the soil in good shape for gardening.
The spent substrate from paddy straw and oyster mushroom have been observed as better substrates in comparison to spent substrate of button mushroom for their use as substrate for vermi composting.2