The contents of fertiliser packaging can seem a little daunting at first glance, but labels explain the composition and nutrient content of the product, helping you to make a well-informed decision about initial purchase and subsequent application in the garden.
1 European Community
approved fertiliser
2 Total phosphorous (P) contained
in the product - however, that
which is soluble in ammonium citrate may not be immediately available for plant uptake
3 The percentage of readily available phosphorous that is soluble in water and should therefore be immediately available for plant use
4 Contact details
of manufacturer
5 Prescribed name, detailing the kind of fertiliser (legal requirement) PLUS ratio of NPK (although the
actual ratio of useful nutrients
is 7.0:3.1:5.8)
6 Total percentage content of
nitrogen (N)
7 In EC fertilisers the type of
nitrogen must be identified - all nitrogen contained in this fertiliser is ammoniacal
8 Phosphorus (P) content as
oxide 7.0, and more usefully
as phosphorus (3.1)
9 Potassium (K) content as
oxide, 7.0 and as more useful potassium (5.8)
Information clarity
Although the details are complicated, the result of legislation is that fertiliser labels all display the same basic information. This allows one garden-fertiliser packet to be compared with another and should show clearly what is being bought. A typical fertiliser packet is shown (above) with an explanation of each item on the label.
Current legislation
The composition, packaging and labelling of fertilisers in Great Britain is controlled by legislation. This may be either British or European; both differ slightly in their content, with EC regulations becoming more prevalent, but both are satisfactory.
Statutory declaration
Fertiliser packaging is required by law to include a number of details, including the following:
- The prescribed name of the product content, such as ‘NPK Fertiliser’
- The major nutrient contents, nitrogen (N), phosphorus (P) and potassium (K)
- Forms in which the nitrogen content is present
- Solubility of the phosphorus content: P and K are usually expressed as their oxide content, followed in brackets by the content of the element
- Levels of secondary nutrients present such as magnesium (Mg) and other trace elements
- Any pesticide content (lawn weed-and-feed products, for example) as well as a statutory declaration to comply with pesticide legislation
- The name and address of the manufacturer
- The guaranteed weight of the product
- An EC product declaration, if the product is EC approved
Usable ingredients
The useful part of fertilisers are the elements, such as nitrogen, phosphorus and potassium, rather than compounds such as phosphorus pentoxide and potassium oxide.
Growmore has a ratio of 7:7:7 for these materials, but is actually 7 percent nitrogen, 3.1 percent phosphorus and 5.8 percent potassium, or 7:3.1:5.8. Therefore it is a high-nitrogen feed, rather than the ‘balanced’ fertiliser commonly assumed. As garden soils are more likely to lack nitrogen than other elements, Growmore is deservedly popular, especially as a spring fertiliser.
Unlabelled products
Materials not covered by fertiliser regulations may be offered as plant foods, without stating their nutrient content. This may be variable due to the parent material (as with pelleted poultry manure) or there may be other purported benefits.
Exempt properties
Fertiliser quality - freedom from lumps, solubility and quality of ingredients - is not covered by the label information. Agricultural fertilisers for example may contain potassium chloride. This is cheaper than potassium sulphate, but some plants are sensitive to chloride content. However, the fertilisers sold to gardeners are almost always satisfactory in these respects.
Application guidelines
Manufacturers of garden fertilisers usually add comprehensive information to help gardeners get the best from their products. Major manufacturers will conduct tests and trials, but generic fertilisers such as superphosphate and Growmore have recommendations based on experience as well as field trials. Guidelines cannot cover every possibility and gardeners may have to use ‘trial and error’ to achieve the best results.
Guy Barter