This article is written specially for UMDIS Mushroom Agency`s readers by Andre Marjanowski, Mushroom Cultivation Consultant from USA.
Inna Ustylovska asked me to write an article about case growing and watering technics in particular. I was struggling, thinking what possibly could interest a modern European grower in the growing systems in the US and Canada, and as well as Mexico, since there are drastic differences and can’t be applied in Europe (and as well vice versa)?
Quick introduction to my mushroom experience, which I have a long history with. I’ve started as a grower in the USA in 1990 and worked my way up to become a vice president and farm director at the one of the largest mushroom company in the US. I have extensive knowledge and experience in all aspects of mushroom cultivation, production and management.
For the past two years, I have been providing advice and consultancy to mushroom farms in the US and Mexico, helping them improve their quality, efficiency and profitability.
As I mentioned above, my personal journey with mushroom cultivation began in the US, where I learned the techniques and methods that have been developed and refined over decades. I have also read many articles that compare and contrast the US system with other systems, especially the Dutch one. Some people may have the impression that the US system is inferior and outdated. I think the US system is a result of adapting to the local conditions and market demands, and it has proven to be very successful and profitable for many growers for well over 6 decades. The US market “prioritized” quantity over quality in order to maximize profit margins, which were always very low. Quality was not neglected, but the volume of production and sales mattered the most. This was the dominant logic behind making this system profitable one. The average production of whites and browns was expected in the range of for whites 38 to 42 kg/m2, while for the brown 33 to 36 kg/m2. This results were achieved by applying the best practices of cultivation, such as optimal watering and timing of the water applications. We made sure to harvest only the mature mushrooms that met the spec size, and avoided picking the small and immature ones that did not meet the proper size, unless market demanded it.
Fig 1. Good stagger with the desired number of layers to achieve high yields was 5 and 5 was how many days 1 flush was harvested. (photo by author)
This is changing now mainly due to labor shortages and market demands. The Dutch style system has now become a popular choice among US growers who are looking for ways to cope with the difficulties they encounter in the business, such as mentioned above, labor shortages. This system offers a high level of efficiency and productivity, as it is based on decades of experience and innovation. Many US farms started to upgrade with this system, but it comes with a high cost that is not affordable for small-scale producers without any government support, which is not offered in the US, unlike in many European Union countries.
Fig2.Modern Dutch system with tilted beds (photo by author)
Fig 3.Growing room with metal shelves in Mexico.(photo by author)
Fig.4. Typical, wooden shelves in PA style growing room (photo by author)
I will try to introduce reader to some of the case hold handling in the US system, as well as what challenges and limitations it faces.
Now, let’s explore the topic of case growing and water management of white and brown mushrooms in America and compare it with the modern methods used in the European countries.
As growers know, case growing is a technique that involves adding a layer of organic material, such as peat moss or other substitutes, on top of, the fully colonized by mycelium mushroom substrate to create a favorable microclimate for fruiting. Watering is an essential part of case growing, as it affects the quality and quantity of the pin set and at the end mushrooms harvested. I will discuss the advantages and disadvantages of case growing in America, and how they differ from the practices in Europe.
Again, many articles have been written on this subject as well, so I will try to give you my own perspective on this.
Fig 5. Black peat moss casing soil ready to pin. (photo by author)
Fig 6. Favorable mycelial growth structure in canadian peat moss day 9 (photo by author)
Canadian sphagnum peat moss is the preferred substrate for most American mushroom cultivators, unlike the black peat that is used in Europe. This difference in substrate composition has led to vastly different growing methods and different challenges on both sides.
Canadian Sphagnum peat moss is mainly derived from partially decomposed Sphagnum moss species from the upper part of the peat bogs. European black peat, on the other hand, is harvested from dipper parts of the bogs where the material is a lot more decomposed and denser.
The main obstacle for American growers to adopt black peat as a casing layer amendment was its high price, largely due to the expensive overseas shipping that made it unaffordable for most of them.
Water holding capacity is the main factor that distinguishes Canadian peat from black peat. While Canadian peat can absorb water up to 20 times its own weight, black peat has a much higher capacity of up to 400 times its own weight. This is the main difference which affects the physical properties of the two types and also how they can be used in the growing process as the casing cover. Growers in the US have tried varies blends with the European peat but the Canadian one still has been the main choice. However, this preference may shift soon due to labor challenges and the adoption of the Dutch system by more farms.
American casing soil consists of sphagnum peat moss and ag lime or hydrated lime, or both, which are mixed together to adjust pH. In addition, CI is added at the time of when peat is loaded on the truck.
On the phase 2 farms (still predominant in the US) casing layer is added after spawn run is complete and on phase 3 farms, just like in the Dutch system, at the same time rooms are filled with compost. This is the point where adding water decisions start to be very different. The type of peat moss is obviously the major factor influencing the decision when and how much water to add, but there are also other factors like for instance the environmental conditions such as evaporation rate, or the expected yield which dictates the watering frequency and amount.
Unlike black peat, which is extracted from deeper layers of peat bogs, Canadian peat comes from the surface level. This gives it a coarser and less dense structure, which affects its water retention and evaporation properties. This peat tends to dry out faster, holds less water than black peat, and requires frequent water applications. Black peat on the other hand, is finer and denser and holds water superbly, and basically doesn’t need water until pinning is established. Also it is delivered in chunks which serve as water reservoirs for mycelium in case hold.
This type of substrate requires frequent and careful watering to maintain optimal moisture levels for mycelial growth. To ensure that the mycelium can grow well in this substrate, we need to water it regularly and carefully. The substrate should be moist and soft, excessive watering can create anaerobic conditions in the lower part of the casing layer, which can inhibit the mycelial connection and growth, and cause it to die. We also need to prevent the mycelium from overgrowing the substrate, as this can inhibit the formation of fruiting bodies.
The following below describes a common watering schedule for case holds with Canadian peat moss.
Fig 7. This water schedule is based on a typical 2000 m2 room with 4 rows of beds, 6 high.
This method of irrigation requires a lot of time and effort, very labor intensive as the water is mostly distributed manually and seldom by a water tree. With the labor shortages this job becomes very problematic because workers have to be allocated from harvesting where they are needed the most to do jobs like this.
To sum up, this article has provided some information about the old American system as compared to the Dutch one, but it may not be very useful for educational or business purposes. The two systems have significant differences that persist to this day. However, in the near future, Americans will need to switch to a more efficient system, and the Dutch one seems a well verified and good option.
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