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"The pinning process and first flush pinset management [for Agaricus bisporus]"
Mushroom News, July, 2008 by Ray Samp
The pinning process is fundamental to commercial mushroom production. It is the process by which the vegetative growth of the compost or nutrient base converts the life cycle of the organism into the reproductive stage. The reproductive structure of Agaricus bisporus is the mushroom - the tissue that matures, drops spores and perpetuates the species. For mushroom growers it is the product that we cultivate and market for financial gain. Let us review what causes pinning and how we can manage it in our cultural systems.
After fully colonizing the compost, the mycelium must grow through the casing layer, a less nutritious medium. The compost mycelium changes form to rhizomorphic development, grows through the casing and arrives at the surface. Once at the surface an environmental change induces the rhizomorphic mycelium to fruit or begin pinning. The environmental change or shock that we administer to the growth at the surface of the mycelium includes air temperature drop, subsequent compost temperature drop, reduction of [CO.sub.2] in the air, and an increase in evaporation. When done in perfect concert, the result is a beautiful flush of the desired amount of quality mushrooms on the first and subsequent flushes.
The desired quality and quantity of mushrooms on any flush in highly subjective. Each market has a certain quality standard and each farm has a certain quantity requirement to pay the bills and have some money left over. As such there is no perfect pinset for quality or quantity for all farms, rather it is the market conditions and budged requirements of each farm to determine. How does a mushroom grower march the desired quantity and quality requirements with actual performance? It can be done but it is the most challenging aspect of mushroom growing.
There are many pinset options from very heavy, even pinsets that give lots of quantity but marginal quality, to sparse staggered pinsets that give great quality and size at lower quantity. Assuming there is a sufficient volume of quality compost, this is largely determined by the frequency of pins/mushrooms per unit area. Controlling that pinset is what determines the result. The decision is up to the management of a mushroom farm.
Factors that influence the pinning process, pinset control and the quality and quantity of harvested mushrooms include:
- Compost quality
- Environmental management
- Post pinning management
- Compost quantity
- Casing soil
Available nutrition directly influences the pinning process. In general, more nutrition increases pinning potential as well as quality and production. Mushroom nutrition comes from the compost. The quality of the compost affects the pinning process. Compost that is unbalanced with respect to recipe or formulation or is incompletely converted in Phase I or II certainly reduces pinning potential and the quality and yield associated with it. Additionally, compost that has been compromised by Trichoderma, plaster molds, or other opportunistic or pathogenic organisms rob nutrition from the mushrooms. Consequently pinning, quality and yield potential are diminished.
Regarding compost quantity, more compost in terms of kg/m2, or more correctly dry matter per square meter, generally increases pinning potential, quality and production. Of course the limitation is the ability to control temperatures and limit mold growth. Excessive compost for the system in question can result in burned out compost during spawn run, problems at pinning and uncontrollable environment during cropping. This is an example of a farm out of control. It must be said that even though more quality compost increases pinning, quality and production potential, each farm has its own limitations regarding how much compost throughput can be handled. Those limitations must be honored.
Supplementation is a way to increase the nutrition base so the mushroom can draw from it. There are a number of supplements on the market. When added at spawning or at casing, supplements can expand nutrition and therefore pinning, quality and production potential. In America as well as other countries around the world most farms use supplement to significant benefit. Depending on rate of supplementation, 10-15 percent more yield can be gained if the product is properly used. Supplement does generate heat and that heat must be controlled. Furthermore, excellent blending of supplements into the compost is required. There is no sense in supplementing poor quality compost.
Now assuming the nutritional base is of optimum quality and quantity, it must be managed in such a way to provide the type of pinset required. If heavy pinning and high production is required, it is just a matter of turning loose the energy that is in the compost. If the objective is more controlled pinning for higher quality, it is a matter of harnessing the energy that is in the compost. This is done through the casing and pinning process. Actually pinning is a continuous process that can be affected before, during and after the point of airing. The casing soil and environmental management are the tools we have to deliver the desired pinset with any nutritional base. Any farm can achieve the desired pinset for its market by correctly managing the casing soil and then the environment during and after pinning.
The casing soil is the first stage of pinset management. It is the medium through which the rhizomorphic mycelium grows and the surface where the pins are established. By manipulating the density and structure of the casing, rhizomorphic growth can be managed to control the number of mycelial receptors, the points at which pins are formed. Therefore a heavy, dense and clumpy casing can limit the number of receptors available to receive the stimulus to pin. The result is a pinset with fewer numbers of mushrooms per unit area. Alternatively if one wants heavier pinning, a less tight, more open casing is better. Consequently the first step in setting the desired pinset lies in the structure of the casing soil.
The second stage in pinset management is controlling the environment at and during pinning. The environmental change delivered to the available receptors also has significant influence on the resulting pinset. Using the environmental factors of air temperature (and resulting compost temperature), [CO.sub.2] concentration and evaporation, the shock can be delivered that will set the pins or fruit the mushrooms. The severity at which the environmental factors are delivered to the mycelium has a large influence on the resulting pinset. In general the more severe the shock, the more pins are formed. The more subtle the environmental change, the fewer pins are formed.
The options of how these environmental factors may be manipulated to pin the crop are limitless. Air temperature can be reduced rapidly or slowly to whatever makes sense to the grower. The same is true for [CO.sub.2] concentration. Evaporation can be managed by fan speed and relative humidity, and may be increased or decreased as required. Finally the means of mixing all these environmental factors to give the desired result is up to the preference and imagination of the grower. Whatever the pinning regime is determined to be, it must be well defined and repeatable. The change and timing of each environmental factor during the pinning process must be clearly understood so it can be delivered room-to-room and crop-to-crop. From that baseline the pinning process can then be modified if the resulting pinset drifts from what is desired.
Post pinning management is the last opportunity to influence the first flush pinset. This occurs applying environmental or physical factors that will stimulate or kill pins as they develop. More mushrooms can be brought forward by environmentally stimulating the pinset during pin development. On the other hand by maintaining a stuffy atmosphere, the first flush can be pruned, doped or choked to reduce numbers of first flush mushrooms to a greater or lesser degree. These actions can also help to stagger or separate first flush mushrooms for several days of harvest. These techniques can be considered advanced and can be accomplished by managing the casing and pinning program.
The final factor that should be considered in pinset management is harvesting. When applying a strategy for growing fewer, larger, higher quality mushrooms, strict control of the harvesting staff is essential. Because the scope of harvesting and harvest management is so broad it will be mentioned but not discussed at this time.
Happy pinning and happy growing!
Agari-Culture Consulting Services
113 Colleen Court
San Marcos, Texas