Mushroom Manure And Lime: Balancing Act?

Mushrooms can grow on various substrates, including manure. When growing mushrooms, pasteurization is often used to remove contaminants from the substrate and give the mushroom mycelium a head start. Lime is sometimes used in this process to raise the pH of the water, making it more alkaline, which kills off contaminants. However, not all types of lime are suitable for pasteurization, and it is important to use the correct type and amount to avoid affecting mushroom growth. While lime can be beneficial for mushroom cultivation, it is not always necessary, and other factors such as the substrate mix and sterilization methods are also crucial.

Lime is used to raise the pH of mushroom manure

When using lime to raise the pH of mushroom manure, it is important to use hydrated lime, which is calcium hydroxide (Ca(OH)2). This type of lime is highly effective at sterilizing, even when used in a highly diluted concentration. It is important to note that hydrated lime made from dolomite has a high magnesium content, which can stunt the growth of mycelium. Therefore, it is recommended to use hydrated lime with a very high calcium content (above 90%) and low magnesium content (not exceeding 10%).

Lime is often used in conjunction with gypsum, which provides calcium and sulfur to promote mushroom metabolism. Gypsum does not typically affect pH, but it helps to keep the pH near neutral by preventing swings caused by metabolites. By using lime and gypsum together, the growth environment is optimized for mushrooms while keeping contaminants at bay.

When preparing mushroom substrates, it is common to pasteurize or sterilize the materials using heat. However, an alternative method is to use a cold water lime bath pasteurization, which is a low-tech and inexpensive approach. This method involves soaking the substrate in a lime bath for 12-24 hours, allowing the lime to raise the pH of the water and kill any competing organisms. After soaking, the substrate is drained and mixed with spawn, providing a clean environment for mushrooms to grow.

Gypsum and lime are used together in the casing mix

Gypsum is a natural element that provides sulfur and calcium to the soil. It is the dihydrate of calcium sulfate (CaSO4 2H2O). It does not usually affect pH. It can be applied to both high and low pH soils. It can be used to correct compacted soil and counteract excessive saline levels. It also removes sodium and improves soil structure.

Lime, on the other hand, is used to raise the pH and make the casing layer inhospitable to competitor fungi. It is also used to pasteurize or sterilize straw substrate. The kind of lime usually added to adjust pH is calcium carbonate (CaCO3), and the carbonate ion part is what raises the pH (makes it more alkaline) by neutralizing acids (hydrogen ions).

When used together, lime and gypsum can have synergistic effects. Lime is insoluble in water and has limited mobility in the soil. Gypsum, on the other hand, is water-soluble and has greater mobility. It can, therefore, improve soil conditions much faster and at greater depths than lime. It will supply calcium to deeper depths, improving subsoil conditions and allowing for greater root growth.

To apply gypsum and lime together, you can use a drop spreader or broadcast spreader. It is important to test the pH levels of your soil before application to determine the right amount of each substance to use.

Pasteurization removes contaminants and gives mushroom mycelium a head start

Pasteurization is a crucial step in the mushroom cultivation process, as it helps reduce potential contaminants and gives the mushroom mycelium a head start. Mushrooms are susceptible to various contaminants, including mold and bacteria, which can outcompete the mycelium and hinder its growth. By pasteurizing the substrate, growers can create a more conducive environment for the mycelium to thrive.

The goal of pasteurization is to reduce or eliminate harmful pathogens, pests, and unwanted microorganisms that could compete with or damage mushroom cultures. It is important to note that pasteurization does not aim to eradicate all living organisms within the substrate but instead seeks to preserve beneficial microorganisms. These beneficial microbes play a protective role against invasive species and assist in breaking down complex materials into nutrients that mushrooms can easily absorb.

One popular method of pasteurization is the cold water lime bath. This technique involves using hydrated lime, which is calcium hydroxide (Ca(OH)2), to raise the pH of the water and kill living organisms. The high pH level created by the lime inhibits the growth of many bacteria and molds but allows the mycelium of mushrooms, such as oyster mushrooms, to flourish. It is important to use the correct type of lime, as agricultural or garden lime does not effectively raise the pH and may contain high levels of magnesium, negatively impacting mushroom mycelium growth.

Another method of pasteurization is hot water pasteurization, which involves submerging the substrate in boiling water above 176°F (80°C) for at least 2 hours. This method is considered more effective at killing contaminants but may be less accessible and energy-efficient than cold water pasteurization. Additionally, pasteurization is generally more suitable for hardy, fast-growing mushroom species, as it does not provide as much of a head start compared to sterilization.

Overall, pasteurization is an essential step in mushroom cultivation, as it helps remove contaminants and gives the mushroom mycelium a competitive advantage. By employing techniques like cold water lime bath pasteurization or hot water pasteurization, growers can create optimal conditions for mushroom growth and increase their chances of success.

Hydrated lime is calcium hydroxide, not to be confused with calcium carbonate lime

When it comes to mushroom cultivation, lime is used for two primary purposes: raising the pH of the growing medium and pasteurization. The type of lime used for these purposes is crucial, as not all limes are created equal.

Hydrated Lime, a Calcium Hydroxide

Hydrated lime, chemically known as calcium hydroxide (Ca(OH)2), is an inorganic compound. It is produced commercially by treating lime with water and can also be synthesized in the laboratory. In its mineral form, it is known as portlandite, which occurs naturally in volcanic, plutonic, and metamorphic rocks. It is a white to beige-coloured odourless powder.

Hydrated lime is sensitive to carbon dioxide and must be stored in a sealed container in a dry, well-ventilated area. It poses hazards to human health and the environment and should be handled with proper safety precautions and personal protective equipment.

Calcium Carbonate Lime

Calcium carbonate lime, on the other hand, is derived from limestone or chalk. It is created by burning calcium carbonate in a kiln above 900°C, resulting in a highly reactive material called burnt lime or quicklime (calcium oxide). With the addition of water, quicklime becomes slaked lime or hydrated lime (calcium hydroxide).

The Role of Lime in Mushroom Cultivation

In mushroom cultivation, lime is used to raise the pH of the growing medium, making it less favourable for competitor fungi. Most mushrooms prefer a slightly alkaline pH, and lime helps achieve this.

Additionally, lime is used for pasteurization, specifically in the cold water lime bath method. This method involves soaking the substrate in water with hydrated lime, significantly increasing the pH and killing off potential contaminants. However, it is important to use the correct type of lime for pasteurization, as calcium carbonate lime does not raise the pH high enough or fast enough to effectively kill living organisms.

In summary, hydrated lime, or calcium hydroxide, is the preferred choice for pasteurization in mushroom cultivation due to its ability to rapidly increase the pH and neutralize contaminants. Calcium carbonate lime, while useful for adjusting pH in the growing medium, is not suitable for pasteurization in this context.

Lime can be used to control mushrooms in lawns

Mushrooms in lawns are harmless to grass but are often considered unsightly. They can develop from buried scraps of construction lumber, dead tree roots, or other organic matter. While some people advocate for simply ignoring the mushrooms or running over them with a lawnmower, others suggest ways to remove them.

One common suggestion is to "sweeten" the soil with lime, making it less acidic. However, this method has been debunked by some sources, who claim that it is ineffective in controlling mushrooms and can even be detrimental to plantings. Lawn mushrooms are often short-lived and disappear on their own, and treating them with lime may not prevent them from reappearing the following year.

Nevertheless, if you choose to use lime to control mushrooms in your lawn, there are a few things to keep in mind. First, test your soil pH using a soil testing kit. If your soil has a pH of 7.0 or higher, it is not advisable to add lime, as it can further raise the pH levels. However, if the soil test shows a pH of less than 7.0, a lime application can help improve the health of your grass and make it denser, leaving less room for mushrooms to pop up.

To apply lime, measure the length and width of your yard and multiply them to estimate the square footage. Refer to the instructions on the bag of lime to determine the proper amount to use per 1,000 square feet, and apply the lime accordingly. Additionally, you can manually remove the visible portions of the fungi and use a mechanical dethatcher to cut through the thatch layer, where mushrooms find their food. By removing their food source and creating a denser lawn, you can effectively control the growth of mushrooms.

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