Answer

How is the volume of growing media measured?

Growing media is compressible and therefore cannot be measured by weight. The standard CEN method is used by Scotts using a 20 litre cylinder. This value can only be guaranteed at the time of manufacture due to the fact that raw materials used in growing media can be easily broken down through transport and handling at end user property. The 20 litre cylinder is filled from a set height to get uniform compression and then weighed. The weight of the bag, bale or lorry can then be related to the weight of the product in the 20 litre cylinder and the volume can be calculated. Due to handling and methods of pot filling, it is unlikely that 1000 litre pots will be filled from 1000 litres of growing media but if the growing media is fluffed up properly and pots are filled gently without forcing, then the numbers will be close.