ISO 18645 Fertilizers and soil conditioners — Water soluble fertilizer — General requirements

ISO 18645:2016 sets out general requirements for water-soluble fertilizers. It was published on 18 March 2016 and is the international counterpart to the national water-soluble fertilizer standards used in major producer markets, including the NY and NY/T series in China.

Water-soluble fertilizers are formulated for delivery through irrigation water or as a foliar spray, which imposes requirements that ordinary solid fertilizers do not face. Complete solubility is the central one: undissolved residue will accumulate in drip emitters, filters and spray nozzles and can shut down an irrigation system over a season.

The standard therefore addresses product requirements around solubility, insoluble residue limits, nutrient content and declaration, and the physical form of both solid and liquid products. Products used in fertigation typically also need to be compatible with other inputs dosed into the same tank, since incompatibility produces precipitation and the same risk of blockage.

The category has grown quickly alongside the spread of drip irrigation and protected cultivation, and the concentration of nutrient in solution is rising with it. A shared specification matters here more than in broadcast fertilizer markets, because the failure mode of a non-conforming product is a blocked system rather than a poor yield response.