The observations from last summer and the past winter concerning the behavior of fruiting bodies and primordia on a substrate enriched with corn meal that would guarantee to achieve the planned yield, were the starting point for a debate regarding the control of the microclimate.
The basic observations are:
- The size and quality of yields collected during the summer were close to the prognoses. At that time the standard microclimate parameters could not be maintained, thus the standard microclimate conditions could not be created either. The application of higher amounts of water into the substrate was required, as this would reduce thermal effect. Yielding proceeded at higher substrate and air temperatures, air humidity, and a higher concentration of carbon dioxide along with significantly faster air movement.
- During winter, upon implementation of the standard microclimate parameters and generally accepted principles of its configuration and reduced dose of water applied in the compost, decreases in the yield and quality of mushrooms were recorded. The yield decrease corresponded to a dose of supplement i.e. higher doses of supplement resulted in larger yield reduction.
- At the end of winter, the „summer” microclimate parameters and stimulus changes of selected elements of microclimate, especially the concentration of carbon dioxide (at the level of several thousand ppm) were introduced. This resulted in the return of yielding to the level of 35 kg/m2 in two flushes, while maintaining the welfare of fruiting bodies in the first flush.
- During the second flush, the introduction of the summer microclimate parameters resulted in extraordinary pinning without distinction of generations. Despite a satisfactory yield, the need for thinning of fruiting bodies and the high cost of harvesting of small primordia forced the search for the procedure that would allow reproducing generations. A significant differentiation of microclimate parameters that were introduced from few to several hours, in order to stimulate and inhibit fruiting bodies turned out to be a good solution. This effect was achieved by the utilization of different susceptibility of fruiting bodies „strong” and weak (the phenomenon of dominance) to these changes.
- Problems in the third flush occurred despite an improvement in the first and second flush yielding.
Conclusions based on the comparison of microclimate and yield between summer and winter:
- The overall fulfillment of nutritional needs changed the approach to the effect of the quality of used products (mainly compost) on the yield of mushrooms. The yield depends on the capability of the control of feeding of primordia and balancing the nutritional and water requirements. This implies the necessity to disregard a creation of microclimate parameters as the goalalone. This illustrates the willingness of recreation regarding their course in accordance to the published graphs. Also, an attempt to find one universal solution that would allow creating the microclimate, which repetition in other halls could provide a reproducible yield reflects the same approach as the development of microclimate.
- Controlling the mushroom feeding requires precise selection of parameters and/or their combinations as well as their modification in behavior of fruiting bodies and primordia in regards to the change that is expected. These actions must be undertaken from few to several hours before the expected change can occur, mainly in regards to a growth rate of fruiting bodies and primordia in correlation to their number per unit of casing surface in comparison to a current status and expected change. Possibilities of controlling the required parameters by using air conditioning and air movement in production hall should be taken into account, as this would allow controlling the growth of fruiting bodies and primordia. Controlling mushroom feeding by changing microclimate parameters is very effective however; it is not an easy practice.
On the other hand, changes in the microclimate after the occurrence of unfavorable effects, for instance dying out of fruiting bodies, tension membrane under the cap, rupture of stipes, water-soaked spots on the surface and water excess in the fruiting bodies that shorten shelf life, and also flat fruiting bodies with a cavity, a small bulk density, etc., can only further destabilize the expected behavior of mushrooms.
Providing high, stable yields of good quality, under conditions of full coverage of nutritional requirements and control of feeding process requires the development of a separate model of control during the course of mushroom cultivation.
The controlling process includes two stages:
1) Differentiation of fruiting body generations and small primordia in each flush in accordance with the principle of diversified growth rate of fruiting bodies of first, second and third generation as well as the stronger and weaker.
2) Maintenance of the growth rate of fruiting bodies in accordance with the process of nutrient transport allowing maintaining welfare (white, shaped fruiting body of high bulk density). Bothgrowth too fast and too slow will worsen the welfare; quality and weight of fruiting bodies. This causes an obstruction between the absorption of water from the casing, transport of nutrients, and weight gain (quality, cell mass and cell membranes). This is the principal mechanism applied in the production process that consists mainly of weakening growth rate by evaporation of water from the surface of fruiting bodies.
Initial assumptions of the control model of the behavior of fruiting bodies and primordia under full nutrient coverage, balanced with accessible water, the nutritional requirements of mushrooms require a new tool that would be able to provide:
- An equal movement of air at any place above the casing (micro-sensor system air flow).
- A range of measurement of carbon dioxide to 12 000 ppm will be increased. It is worthy to mention that under the conditions of balanced nutritional requirements of mushrooms that the concentration of carbon dioxide in the cultivation hall raises easily.
- Measuring the diameter of growth of fruiting bodies with a camera that would further allow the analyzing of the image.
- Measurement of life activity of fruiting bodies and primordia by controlling the temperature difference between the casing and fruiting bodies and primordial, and among fruiting bodies and primordia with the thermographic camera.
- Measuring the amount of applied and evaporated water by continuous measurement of the weight of the separated section of the crop.
- Integration of these variables measurements with the developed algorithm regarding the control of behavioral changes of fruiting bodies and primordia.
It is essential to develop a control algorithm. Observations of mushroom behavior under conditions of complete feeding indicate the need to take into account the following changes occurring between the microclimate and the fruiting bodies and primordia, and in particular:
- The influence of stimulus and the changing of the direction of the linear course of microclimate parameters. At phases regarding the differentiating of fruiting bodies and small primordia, small changes of microclimate with considerable variation are required, but for a period of few or several hours in order to give an effect of stimulus – behavioral change. During fruiting, when the course of the parameters should be linear, it is necessary to periodically change the direction (vector) in order to maintain the desired growth rate through a small variation of microclimate parameters with prediction and monitoring the pace and direction of changes. This is to guarantee a transport of nutrients coordinated with the propagation and growth of cells and their walls at the rate imposed by the level of evaporation.
- The stimulation of excessive growth of primordia causes intense evaporation and accelerates the transition of primordia to the production of spores. It results in stopping weight increase; flattening and opening of primordia.
- Higher temperature of air and substrate. The use of the principle that the rate of life processes increases by 10% as geometric progression at an increase of temperature by 1 ° C. During the growth of primordia the temperature is 19-20 ° C and the substrate up to 23 ° C.
- Not increasing the temperature difference between the air and the substrate. Keeping control of the substrate temperature during yielding is dependent on the water content in the mycelium and the substrate.
- Increasing the role of carbon dioxide concentration. To maintain the welfare of fruiting bodies a concentration at the level of 2500 to 3500 ppm is required and for some varieties it may be higher. However, to inhibit the growth of fruiting bodies and small primordia, the carbon dioxide concentration at a level close to 8-10 000 ppm is efficient. In addition, it is required to monitor the shape of the bulbous fruiting bodies.
- Maintaining a constant water shortage, and not the level of air humidity in the hall cultivation.
Balancing the nutritional needs in accordance to water requirements and with the expected yield does not automatically guarantee success. The system of control of density of primordia, their weight increases at a constant preservation of their welfare needs to be implemented. Controlling the growth of fruiting bodies and primordia is a significant part of the new approach. Balancing the supplement with water is relatively simple, but it determines the further expected course of cultivation. The current knowledge about the control of feeding is the result of practical measures. It will require a broader analysis, based on scientific data and, in consequences, the development of a new algorithm and the tool allowing independently and effectively control the growth of fruiting bodies and primordia through changes in microclimate parameters.
The initiation of primordia is an independent issue, which requires a separate discussion.