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CULTIVATION TIPS DLV PLANT MUSHROOMS Filling thickness and quality


By Erik Polman, DLV Plant Mushrooms e.polman@dlvplant.nl


Many growers are complaining about mushrooms in the second, and sometimes third, flush maturing too quickly. These mushrooms fail to develop into good quality fruits with a high individual weight (see photo). The number is also difficult to estimate. The main culprit of this problem currently seems to be an uneven, or too low, filling weight, or insufficient compost activity. There is no spontaneous evaporation, which results in inadequate CO2 production. Setting the minimum position of the fresh air inlet a little higher and lowering the minimum CO2 concentration should ensure enough evaporation. During summer, some growers fill using slightly less compost in order to facilitate ea- sier temperature management, or less supplement is added. This will not lead to many spectacular differences in mushroom quality in the first flush; however, the difference will be obvious in the second flush. Equally on farms where the filling thickness is difficult to regulate- such as tray growing farms- quality-related problems occur in patches where the compost layer is thinner, if the layer applied in the first place was thinner than average. If the compost activity also decreases sooner than usual, less water is sprayed. This dehy- drates the casing soil making it more complex to properly steer and manage the second flush. Properly assessing the structure and moisture content of the compost before filling will help estimate better how thickly to fill the beds. This will virtually do away with the need to alter the thickness during filling, while at the same time having a positive effect on unifor- mity. We also notice differences in filling thickness between rooms, which can also cause some variation in activity levels. In this case, each room will require a different volume of water, a different air inlet position and CO2 concentration to achieve good production results. Make sure you have a clear overview of the filling data per room so you can continue to take the right management decisions.


Connection capacity and alternatives


By Jan Gielen, DLV Plant Mushrooms Manager / Specialist klimaat & energie j.gielen@dlvplant.nl


Despite the current challenging situation in the Dutch mushroom growing sector, expan- sion projects are still realised on a regular basis. During the planning stage aspects like the availability of compost and casing soil, and securing a market for the mushrooms and the spent compost are factored in, but a sometimes overlooked issue is whether energy sup- plies are sufficient. When upsizing an existing facility the gas and electricity connections already installed are tailored for a certain load. If these arrangements cannot cope with the new load requirement, you can apply for a capacity increase or have new connections installed. The costs involved can though be considerable, and in some cases a capacity increase is impossible, as the transmission system that distributes power is already loaded to maximum capacity. What alternatives are available for gas supplies if the connection capacity is limited? The most suitable way to produce steam for cook out is via combustion; e.g. a boiler powered by gas, heating oil, wood or another biomass. The most practical approach is to connect the boiler to the existing gas connection. There are alternatives to gas that can be used for heating. For instance a ground source heat pump (GSHP), which can be used to supply a substantial proportion of the basic cooling and heating requirement. The heat source in the ground usually has a temperature of approx. 14 °C, while the cold source is approx. 9 °C. These sources are connected to a pre-heating/pre-cooling unit installed either in a central duct, or individually per growing room. If a so-called low temperature heating system (45-35 °C) is used for additional heating, use can be made at this temperature level of the heat produced by a heat pump or heat recovered from ( part of) the condensers. In winter, when more heat is required, or when the cooling unit is idle, a small, gas-fired bypass boi- ler can be used, or a heat exchanger connected to the boiler. What alternatives are available for electricity if the connection capacity is limited? Additio- nal to the GSHP mentioned above, which can generate a basic supply for cooling purposes and in doing so save electricity, solar panels are very suitable. They are particularly well- suited to generate electricity for the cooling or heating pump, as especially in summer months the cooling requirement is virtually parallel to the power generated by the solar panels.


A combination of GSHP, heat pump (or cooling unit with heat recovery) and solar panels, paves the way for working with a limited connection capacity without making any conces- sions to the overall energy supply. And, this translates to a sustainable way of providing for a significant proportion of energy on the farm.


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