ISO 18642 Fertilizers and soil conditioners — Fertilizer grade urea — General requirements

ISO 18642:2016 sets out general requirements for fertilizer grade urea, the most widely traded solid nitrogen fertilizer in the world. It was published on 7 July 2016.

Urea has always been traded to national specifications that differ in detail while agreeing on the essentials: high nitrogen content, tight limits on moisture, and control of the principal impurities that determine how the product behaves in storage and in the field. This standard provides the common reference those national specifications lacked.

Two quality parameters dominate the commercial assessment of urea. The first is nitrogen content, which sets the product's value per tonne of nutrient. The second is biuret, a condensation product formed during manufacture that inhibits plant growth and can damage germinating seed; separate ISO work under ISO 18643 standardises its determination by HPLC.

Physical quality — granule size, size distribution, crushing strength and resistance to caking — determines whether urea can be blended, spread mechanically and stored without setting into a mass. For a product traded in millions of tonnes a year, a specification that is not shared between buyer and seller is an argument waiting to happen.