The Fertilisers Regulations 1991

8.  For basic slag, Thomas phosphates, Thomas slag, basic slag medium concentrations and granular basic slag the declared contents and solubilities of phosphorus pentoxide may be expressed as a range of 2% by weight. The forms of nitrogen and solubilities of phosphorus pentoxide shall also be expressed as percentages by weight of the material. Otherwise, and subject to paragraph 9 below, the declared contents referred to in paragraphs 6 and 7 shall be expressed as a percentage of the weight of the material and shall be given as whole numbers or, where necessary, to one decimal place.

For fertilisers in Sections A, B and C of the table in Schedule 1 for which a declaration of secondary nutrients or trace elements is made, the total amount expressed as a percentage by weight of the fertiliser shall be given. In addition the water soluble content shall also be expressed as a percentage by weight of the material where the soluble content is at least a quarter of the total content for secondary nutrients or a half of the total content for trace elements. Where the secondary nutrient or trace element is totally water soluble only the water soluble content shall be declared. Where all or part of the trace element is chemically linked with an organic molecule the chelated content of the trace element present in the material shall be declared immediately following the water soluble content, followed by the terms `chelated by' with the name of the organic molecule, as set out in table 2 to this Schedule, or its abbreviated form.