What makes a mushroom sprout out of soil soon after monsoon but not after sprinkling water?

A majority of mushrooms that sprout directly from soil during the monsoons belong to the Tricholomataceae family. Calocybe indica, a beautiful and white coloured umbrella shaped mushroom is the most prominent among them. This genus originated from the forests of West Bengal. Today, its variants are cultivated commercially under the popular name 'Milky mushroom'.

Mushroom spores are hyaline, broadly ellipsoidal, thin-walled with prominent apiculis. Under favourable conditions such as low temperature, high relative humidity and faded light, the spores germinate and the mycelial spread resumes. It takes nearly 50 days for the completion of the mycelial spread and subsequent emergence of the sporophores. During the entire period of mycelial spread, very high relative humidity, 25-30 degree Celsius temperature and faint light are necessary. Unlike sprinkling water, monsoon changes the entire microclimate. Sprinkling cannot reduce the atmospheric temperature, control sunshine or maintain high relative humidity for long time whereas the monsoon's prominent effects will be the high or stable relative humidity coupled with decrease in the intensity of sunshine, which are necessary for spawn spread. Mushroom beds, after inoculation with mushroom spawn, should be kept for 30 days under darkness with high atmospheric humidity. After the mycelial spread the plastic cover of the bed is removed, sterilised casing mixture composed of equal quantities of soil, sand and cowdung is loosely spread over the bed. Only faded light is permitted but high humidity is maintained. After about two weeks mushroom start sprouting.

Source: The Hindu