ISO 7851 Fertilizers, soil conditioners and beneficial substances — Classification

ISO 7851:2022 establishes the international system for classifying fertilizers, soil conditioners and beneficial substances. Edition 2 was published on 29 April 2022 and replaces ISO 7851:1983, whose classification scheme had become badly out of step with products that now dominate the market.

The primary axis is nutrient content: straight nitrogen, phosphorus or potassium fertilizers; binary NP, NK and PK products; ternary NPK products; secondary-nutrient fertilizers based on calcium, magnesium and sulphur; and micronutrient fertilizers. Organic fertilizers, organo-mineral fertilizers, fertilizers with added beneficial substances, and fertilizing product blends form the other principal families. Annex A sets out the nutrient-based scheme in full.

Auxiliary criteria refine the picture. Products are further characterised by their effect, by physical form (powders, granules — described through metrics such as SGN, D50 and UI — and liquids), and by acidity or alkalinity, distinguished between chemical effect in aqueous solution and physiological effect on medium pH.

The 2022 edition matters most for what it added rather than what it restated. 'Beneficial substances' — plant biostimulants and beneficial nutrients — now sit inside the classification framework, having existed outside it when the 1983 edition was written. Organo-mineral fertilizers and fertilizing product blends receive the same treatment. A classification standard that cannot name a product category leaves that category unregulated and unbuyable.

For exporters the practical consequence is straightforward: a product description that does not map onto an ISO 7851 category is difficult to place in a tender, a registration dossier or a cross-border specification. Classification is the first thing a buyer checks and the first thing that gets argued about.