The claim described in this document concerns the improvement of availability of confined nutrients in the soil or rhizosphere by a plant biostimulant. This document is aimed primarily at manufacturers, laboratories, researchers, technical centres, companies that will put the products on the market, notifying authorities, notified bodies, and market surveillance authorities. To be in compliance with this standard, it is important also to follow the Recommendations and Quality Criteria described in the Standard of General Principles EN 17700-1: 1.