The most commonly heard complaint nowadays is the sub-standard quality of the second flush. The development into good-sized fruits in particular is disappointing. Mushrooms are too light, the number of mushrooms is unpredictable and they mature too quickly. Examining all factors often shows a filling weight that differs from growing room to growing room. This reduces the predictability of the crop. Especially with a too low filling weight both the quality and quantity of the second flush is unsatisfactory.
A low filling weight is often motivated by economic reasons For many growers compost represents 25 % of the cost price so a low filling weight is considered a good way to save money However the contrary is usually true A low filling weight loses activity during the first flush and the second flush has more difficulty developing. This premature loss of activity also means no water can be sprayed during the first flush, resulting in too dry compost. The second flush doesn’t have enough moisture to gain weight.
A casing soil that has been allowed to dehydrate, can never recover a good moisture content. In many cases it's not advisable to fill less than 90 kilos of compost per square metre. Many farms even fill up to 95 kilos and generally with encouraging results. We also recommend paying extra attention during filling to ensure the filling weight is identical throughout the entire growing room. Good teamwork between the grower filler and lorry driver can help save money in this case.
Henk van Gerwen, AdVisie ‘The mushroom cultivation advisors’