After the last water during the incubation in the casing soil, the grower wants the mycelium to grow onto the surface. To ensure a good recovery of the mycelium in this period the right settings for the room climate are essential.

An RH at a minimum of 95%. A very slow air speed, if possible zero and an adequate room temperature. That room temperature should be as close to the optimum for vegetative growth as possible. That optimum temperature is 25° C to 26° C.
This means often a room temperature of around 21° as a minimum. Then the mycelium has the right conditions to grow onto the surface.

The next question is: how high do I let it grow ?
Higher means better control of the number of primordia, so no surprises about the number of mushrooms growing out. Higher also means easier picking so a higher pick rate. Another positive experience is that clustering is easier avoided.

But the big dis-advantage of having the mycelium higher on the surface is that the climate conditions have to be perfect. The influence of the climate onto the mycelium and the primordia is bigger. So one moment of for instance too low RH means that you will lose primordia. Deeper mycelium is also easier to stagger the mushrooms so that is an advantage too. Another point is the fact if the grower can stop the mycelium when it grows too high. Overlay as that is called makes the outgrow of primordia more difficult. They come from underneath the blanket of mycelium.

So what determines the choice?
Both ways have their pro’s and con’s.
But for me the crucial point to choose a way is the technical capacity of the farm and the experience of the grower. If you are able to stop the mycelium at all times, still create the stagger and have perfect control of the environmental conditions, grow white.
If you are not sure of all this, grow deeper into the surface of the casing soil. So grow blacker.
Generally blacker is safer.

A few years ago, it was standard practice to give a significant amount of water in the first few days after casing. It was common to see people aiming for maximum watering, with 35 liters per square meter being standard and 40 liters considered even better. The goal was to adjust the moisture in the phase 3 compost, with the aim of reaching a moisture level of 72% or more.

Today, clients around the world are seeking better-quality mushrooms. Every grower aspires to cultivate the perfect mushroom.

The Perfect Mushroom

The ideal mushroom looks the same everywhere in the world:

• It has a good color and shape
• It is heavy and dense
• It has a long shelf life
• For us as growers, it must be financially viable, producing a high yield with minimal costs

This type of mushroom grows only when all conditions are in balance:

• The compost contains all essential nutrients that are accessible to the mushrooms.
• The water content in the compost is available to the mushrooms, but not in excess. If the mushrooms have to work a little to access this water, it will produce a stronger mushroom.
• Compost activity should be low during picking. If the compost is too active, water may be forced into the mushroom during picking. This can be managed by adjusting the filling weight or compressing the compost.
• The climate in the growing room should be natural; this means avoiding extremes in air temperature, CO2 levels, or fan speed.
  
  

Compost Filling Weight

Many farms worldwide still prefer to fill a large amount of compost per square meter. It’s often believed that more compost produces more mushrooms, which is true. However, this added compost must also be managed carefully. Typically, if you increase compost volume, you’ll need to employ extreme climate controls to manage compost activity, such as high fan speed or low air temperature. During the first flush, this compost activity often makes it difficult to maintain a gentle climate. A gentle climate in the first flush is crucial for producing high-quality mushrooms. It doesn’t help to have an excellent third flush if the majority of your first-flush mushrooms are damaged due to extreme climate adjustments for compost activity. This increased activity dries out your compost and casing, causing issues for the second and third flushes.

Watering and Compost Activity

After filling phase 3 compost, the mycelium is damaged and needs time to recover. Adding too much water in the first two days after filling halts mycelium growth. The mycelium cannot spread over the compost because water sits on the outside of the compost. In these cases, high compost activity occurs because the mycelium is competing with the water. It is much better to allow the mycelium to regrow (recover) for two days after filling, only adding small amounts of water to keep the casing moist.

Watering on Different Types of Compost

A watering schedule depends on various factors:

• When the compost is not fully colonized with mycelium and remains active, wait before watering to allow mycelium to incubate. Once the mycelium starts growing into the casing, you can gradually increase watering.
• When the compost has a long or coarse structure, you can begin watering earlier. The loose structure allows excess water to drain to the bottom of the compost.
• When you have a short or soft compost, be especially careful with watering during the first two days. This type of compost acts like a sponge, absorbing water in its top layer. This prevents the mycelium from regrowing in the upper layer, creating a weak connection between the compost and casing.
• If you fill with warm or highly active compost, it’s better to minimize watering on the casing, adding just enough to keep it moist. Some growers add large amounts of water to cool down the compost, but this only halts mycelium regrowth and increases activity.
  
  
  

Mushroom growers worldwide face the same problem: there are times during cultivation when the compost exhibits either more or less activity than desired. This can happen right after filling the compost, during ventilation, or if the compost temperature rises too quickly during the first flush, which can severely impact mushroom quality.

Most farms have this under control, but each grower must find the optimal formula for their own operation. This principle can be compared to a balance: if you change something on one side, you must adjust the other side to maintain equilibrium.

The entire process starts with filling the compost in the room. There are a few important factors to consider at this stage. The moisture content and structure of the compost are crucial for the expected activity right after filling. Dry compost with a lot of structure will show high activity immediately after filling. This compost should always be filled thicker to achieve the desired kilograms per square meter. This extra thickness is mainly filled with air, which acts as a buffer for heat.

Once the compost becomes active, this air warms up and is very difficult to cool down again. Compact it as firmly as possible. For wet compost with little structure, do the opposite: fill it loosely and avoid watering immediately after filling.

Mycelium Growth during incubation
If everything proceeds normally during the growth phase of the compost, the first signs of activity can be seen around day 9 after spawning. This activity increases as the compost continues to grow. By day 15, the compost should be fully colonized, and activity will start to decrease. If, for some reason, the compost needs to be covered or removed from the tunnel earlier, this activity will continue in the growing rooms. At that point, controlling this activity becomes very difficult because the casing soil acts like a blanket, retaining heat in the compost. In such cases, keep the air temperature in the room very low to maintain the compost temperature at 26°C. This will also cool the casing soil, preventing mycelium growth in it.

Supplementing
Supplementing the compost provides extra activity. The level of activity depends on the type and amount of supplement used. Typically, 15 kilograms of supplement per 1,000 kilograms of phase 3 compost yields optimal results. However, this depends greatly on the compost. If the compost has a high nitrogen content, 15 kilograms might be too much. Supplementing is an excellent way to increase both the quantity and quality of mushrooms, but the compost must be free of competitive mold infections. Infected compost can react negatively to supplements because these are also food sources for competitive molds, which can harm the mycelium or mushrooms, negating any benefits of supplementation.

Filling Weight
Filling weight is a crucial factor for compost activity and significantly affects the total mushroom yield. Generally, a 10% increase in compost results in a 10% increase in mushrooms. This is true, but the climate unit must be able to manage the additional compost. Again, it's about balancing the ability to handle increased activity with the potential yield benefits.

As you can see, the desired but sometimes troublesome activity of compost depends on many factors. Literature provides ideal filling weights, but in practice, it varies from farm to farm. Growers must determine the ideal ratios for their specific operations.

Total Mushroom Service
Jeroen van Lier

Generally picking is considered by many as a low education job. But on the other hand, we rely on our picking force to deliver a good quality mushroom, meeting the customer demands. No bruised mushrooms, no nail or knife damage, right stem length, straight cut stem, no weak mushrooms in the punnet and for all, the right size. And that is where many things go wrong. It is fairly easy to learn the pickers the right way of picking. Twist and do not pull. Do not take to many mushrooms in one hand so they do not get damaged and put them caps up into the punnet. But getting the calibration right is a constant struggle. Pickers tend to have the habit to pick too small and this will cost you money. They simply pick the mushrooms that were meant to be picked tomorrow. An extra thing to that is that pickers lose the bonus while working really hard.

For the right calibration there are many tools like fruit grading rings, grading cards and other different tools. But the easiest tool they have in their hands: the knife.
The knife most used in mushroom growing is the curved knife and the length of the blade is exactly 60 mm. The calibration most wanted on many farms is 55 to 60 mm. Generally, this size is picked first before thinning out. And this is just the size of mushroom that is as wide as the length of their knife. They just have to keep the knife just above the mushrooms to judge the size. This way the mushrooms can be calibrated before they are picked and they will not be damaged by any other form of grading tools. The rings only let mushrooms through which are small enough. The bigger mushrooms get stuck and will be damaged. But the mushrooms that go through easily are too small and that is the calibration the picker will harvest. By using the knife not only there will be no damage but it is also faster.

If a smaller calibration is harvested like a 40 mm mushroom, a line can be made on the blade with a marking pen. Especially new pickers will be very fast in learning this trick. By banning the calibration rings also, the hygiene on the farm is served. Because these rings are hard to clean and experience learns that they are always dirty and are taken from room to room.

Give it a try and your harvesting staff will be happy.