Creating the ideal moisture content during pin heading and development of the first flush involves many factors. Not only the moisture content of the compost hugely influences the amount of sprinkling water used, the speed of mycelium colonization in the casing soil (influenced in turn by cac-ing being applied and how much) also contributes.
Crucial with the right moisture content is not only the question of when and how much to sprinkle, but more importantly factors that cause dehydration. Too much air circulation can lead to unnecessary loss of moisture. Over active compost also gives moisture loss and working with excessively high compost temperatures - including at the start of blow down - causes too much needless evaporation.
An extra handicap for growers taking a conscious choice not to sprinkle during the first flush in order to achieve the best possible quality - in a similar situation this turns into a bottleneck. The result is premature ripening and casing soil coming out of the first flush too dry.
Jos Buth, C point