Evaluation of the Effect of Different Composition of Casing Soil on the White Button Mushroom (Agaricus bisporusLange) Yield and Quality Traits

Today, due to increasing world population, food needs to be provided from different ways. The white button mushroom has also become an important constituent of a healthy diet. Their nutritional value relies on relatively high protein, minerals, vitamins, essential amino acids content and low calories. Mushroom mycelia growth and mushroom development are not only related to genetic factors but also depends on environmental, chemical, and microbiological conditions. Casing soil can protect the compost against desiccation, supporting the mushroom against pests and diseases and providing sporophores development and development and growth of mushroom by gas exchange. Casing layer provides an environmental change in which the mushroom shifts from a vegetative stage to a reproductive one due to microorganisms in the casing soil. Casing soil bacteria influence productivity, product quality and uniformity. Physical and chemical properties of a good casing should be high porosity and water holding capacity (WHC), pH range from 7.2 to8.2, low content of soluble inorganic and organic nutrients and free of disease and pests. Many materials, alone or in combination, have been used as casing both commercially and experimentally, although only a few have been shown to be practical application. Peat is generally regarded as the most suitable casing. Because of its unique water holding and structural properties, it is widely accepted as ideal for the purposes of casing. Peats has a neutral pH and because of it contains organic matter and granular structure can stay porous even after a consecutive irrigation, hold moisture, allows appropriate gaseous exchanges and supports microbial population to release hormone-like substances which are very likely involved in stimulating the initiation of fruit bodies. Peat and limestone commonly used as a casing soil, however problems associated with its use, especially viability, depletion of reserves and alteration of ecosystems, have led to the search for alternative materials.
In order to investigate the effect of different compositions of casing soil on the white button mushroom (Agaricus bisporus Longe) cultivation, an experiment was carried out in laboratory of mushroom research, Department of Industrial Fungi Biotechnology, Iranian Academic Center for Education, Culture and Research (ACECR- Khorasan Razavi), in 2015. The experiment was conducted in a completely randomized design with 8 treatments and 3 replications. The treatments were including peat soil (100%), peat soil (60%) vermicompost (40%), peat soil (60%) cocopeat (40%), peat soil (60%) activated carbon (40%), peat soil (60%) spent mushroom compost (40%), peat soil (60%) vermicompost (30%) activated carbon (10%), peat soil (60%) cocopeat (30%) activated carbon (10%), peat soil (60%) spent mushroom compost (30%) activated carbon(10%). The treatments were applied on the compost block (40 × 60 × 20 cm sizes), that inoculated with the mushroom spawn, commercial line A15. The investigated characteristics including mushrooms yield, mean of mushroom weight, number of mushrooms per square meter, mean of stipe length, mean of cape diameter, which was measured in each harvest flash, separately. The traits were measured three times from casing to first harvest flash and harvest period.
The results showed that the longest duration between casing to first flashing belonged to peat soil (60%) spent mushroom compost (40%). The lowest duration belonged to peat soil (60%) cocopeat(40%), peat soil (60%) activated carbon (40%) and peat soil (60%) cocopeat (30%) activated carbon (10%). Treatments with the lowest duration between casing to first harvest flash, produced the most yield. The results also revealed that casing soils treatments contained cocopeat(40%) and cocopeat(30%) active carbon(10%) had the highest yield, fruit number, fruiting period and shortest duration from casing to first harvest flash as a good characteristic, although the mean of mushrooms weight and diameter of cape were lower than other treatments that it affect on marketing quality. Two treatments including spent mushroom compost (40%) and spent mushroom compost (30%) active carbon(10%), had the lowest yield, fruit number, fruiting duration, the longest duration between casing to first harvest flash as an unfavorable characteristic, although these treatments had the highest mean weight and cape diameter. Overall, the results showed that spent mushroom compost utilization as casing soil is not economically cost-effective.