In article , Nick Maclaren
writes


To clarify, you are referring to the 'composts' sold in garden
centres. The sort of thing that you get by composting household
organic waste is entirely different, and contains a lot of nutrients.

Commercial composts contain varying amounts of nutrients according to
whether they are described as seed, potting, growing etc., also
according to their John Innes category if given.
--
Alan & Joan Gould - North Lincs.