Only since the 1950’s mushroom cultivation has used more modern techniques, by using properly air conditioned rooms or cells, soils made of wheat straw, pasteurized and covered with peat. The cultivation cycle of the complete champignon mushroom lasts 100-120 days and can be repeated 2-3 times in a year. To the kingdom of mushrooms belong heterotrophic organisms whose reproductive means consists of spores emitted from the gills of the cap. The fruiting body of the mushroom (the edible part) consists of a stalk and a cap or carpophore, while below the stalk in the soil there is a vegetative structure organized in cells forming filamentous and branched structures called hyphae or primary mycelium which do not differentiate into tissues.

Also known as prataiolo mushroom or white mushroom, champignon mushroom, whose scientific name is Agaricus bisporus, belongs to the Agaricaceae family. There are four different groups of varieties subdivided according to the coloration of the cap: white varieties; brown varieties; intermediate varieties (cream, white-ivory); hybrids. White varieties are characterized by white carpophores, with a delicate surface, usually small in size (4-8 grams). They include strains endowed with greater or lesser speed of production growth. The production of white varieties is mainly destined to the fresh trade. Brown varieties are not much cultivated, they have medium-large carpophores, of a color which varies from light brown to dark brown with a light stem. From researches carried out at the beginning of the century, multispore colonies were obtained and selected in order to obtain the white varieties now widely cultivated. The intermediate varieties (cream, ivory-white) have medium-large fruiting bodies (8-12 grams) similar to those of the brown varieties, light color, presence of brown scales. The gills and spores of mature carpophores are very dark in color. These are varieties suitable for mechanical harvesting. Carpophores, if left to develop, can reach large dimensions. They are not very sensitive to virus infections. In 1976 at the Experimental Station of Horst in Netherlands were started researches aimed at crossing white varieties with intermediate varieties. They obtained hybrids called “Horst U-strain 1-2-3…”. They combine favorable characters of the two varieties such as smooth and white surface, pinkish gills, short stem. The high quality of the hybrids and the good production have favoured a rapid use in mushroom farms. The production is commercialized both fresh and transformed.

Before realizing a mushroom farm, in order to avoid failures, forcing or excessive technical interventions, it is advisable to verify that the area interested in the plantation is climatically suitable for the cultivation of mushrooms. The costs of insulation and labor, in fact, increase considerably where the temperatures are maintained above 25 ° C for long periods. A mushroom farm requires a relatively modest area and it does not matter if it is of little agricultural value. Instead, it is vital that there are no water supply problems. The most important thing in the cultivation of champignons is therefore the substrate. The growing medium should be made of 1/3 wheat or oat straw or barley straw, 1/3 peat and forest soil, 1/3 well-decomposed horse manure, or alternatively: 1/3 well-decomposed horse manure, 1/3 white peat, 1/3 sandy soil. Then the growing medium is placed in wooden boxes or plastic bags and layered (e.g., straw, peat, manure, and peat on top). After having watered the soil abundantly, a phase of fermentation of the stratified mass begins (useful to remove antagonistic bacteria and fungi) lasting 5-15 days, depending on the “freshness” of the manure and the material used. In modern mushroom farms this operation consists in a real pasteurization of the substrate with steam, it is done in special cells with temperature, humidity and CO2 in controlled conditions. Subsequently it is possible to sprinkle the culture medium with mycelia and cover it with some wet peat (the mycelium must be at a depth of 4-5 cm). This phase is called incubation, fundamental are: the humidity that must remain between 80 and 100% (detectable with an appropriate hygrometer) and the temperature that must not exceed 22-23°C. These mushrooms should be watered little and often, the idea is to keep the layer moist and not soaked with water.  After about 12-14 days from the incubation, we cover the mushroom bed with a layer of soil in which the mycelium will develop, the temperature is brought to 17°C. After about 10 days we assist to the appearance of the first hats.

Crop care and irrigation

During the period of sprouting and harvesting it is necessary to do the following cultural cares: Watering: for every potential kg of mushrooms it will be necessary about one liter of water per square meter. If this amount seems insufficient, it is advisable not to increase it, but to water twice a day rather than too much at once. It is very risky to distribute water when the carpophores are formed and it should not be necessary to water during the peak of the sprint if it was done at the right time. If the mushrooms are not completely dry by the time they are harvested, they will easily spoil and there is a possibility of bacterial spots appearing on the surface of the cap. Watering procedures for the second harvest are the same of the first one, whereas for the third harvest it will be necessary to pay attention because mushrooms will be lesser in number and therefore water needs will be adapted to the yield.

Ventilation: during the whole harvesting period, and especially when mushrooms are very numerous, ventilation must be abundant because between mushroom heads are formed gaseous pockets mainly made of CO2. Moreover, the heat produced in the beds during the marking and formation of carpophores must be eliminated, especially through the evaporation of water from the upper layer of the growing medium.

Temperatures at harvest: During harvest, the air temperature should be maintained at 15-16°C, while the temperature of the beds will be slightly higher. In case of a very abundant sprint, the air temperature should be lowered to 14-15°C. If temperatures are slightly higher, fungi grow faster, but this is at the expense of quality especially during the first sprint because diseases and pests such as rot, web mold, and nematodes develop more rapidly.

The specific adversities of Agaricus bitorquis are mainly caused by bacteria, fungi and various types of viruses. The defense is mainly based on the principles of preventive control by realizing good general hygienic conditions in the environments, with disinfection and air filtration and pasteurization of the substrates used. Still today there are no varieties resistant to diseases caused by moulds, however it has been found that Agaricus bitorquis is very resistant to virosis. Among the moulds indicating wrong agronomical techniques there are, for example, the Web Mildew or Spider Web (Dactylum dendroides) which indicates stagnant air and excessive air humidity or the Yellow Mold (Chrysosporium spp.) which indicates mistakes in pasteurization. Moreover we can mention: Olive mold (Chaetomium spp.): presence of ammonia, high pH, compound too fermented, wet and compact, Chalk (Scopulariopsis fimicola): presence of ammonia, inaccurate pasteurization, excess of nitrogen and humidity of the compound and Coprinus (Coprinus spp., Trichoderma spp.) microorganism favored by excess of ammonia, high pH (±-8) and compound too wet. In addition, fungus gnat, mites and nematodes can develop if conditions persist.

Production and harvesting

A volata is defined as the sprouting of mushrooms. The average number of sprouts is 5 in the case of A. bisporus, while the period between the peaks of two sprouts is about one week. Mushrooms do not sprout with a regular pattern and their fructification is primarily evident at the edges of the beds. Usually, the first, second and third sprints are the most abundant and immediately afterwards the maximum production, as well as the total one, decreases rapidly. The quantity of mushrooms to be harvested is maximum after 3-4 days, after which the intensity of the volata gradually decreases and finally stops after a few days.

The mushrooms are harvested on the cultivation bales by hand according to size because they are delicate and break easily after harvesting are placed in suitable containers.

In order to understand whether mushrooms are ready to be harvested it is necessary to touch the inner part of the cap; in case the membrane covering the gills is elastic the mushroom is ripe, in case the membrane is torn the mushroom is too old, moreover they must have a nice light white color. When harvesting mushrooms it is recommended to delicately take the cap between fingers and remove it by slightly rotating the hand.