(28)Economic operators should be responsible for the compliance of EU fertilising products with this Regulation, in relation to their respective roles in the supply chain, so as to ensure a high level of protection of the aspects of public interest covered by this Regulation, and also to guarantee fair competition on the internal market. Whenever appropriate, manufacturers and importers should carry out sample testing of the EU fertilising products that they have made available on the market, in order to protect the health and safety of consumers and the environment.