About Us

The Phosphite Biostimulant Stewardship Group (PBSG) was created by a group of like-minded biostimulant manufacturers. Our aim is to persuade the European regulators to allow the continued use of phosphite as a biostimulant, enabling subsequent EU registration under biostimulant regulations.

Phosphite has been used as a biostimulant for many years. It is a well-established, cost effective, proven technology used by farmers across Europe on a wide range of crops. The PBSG has collaborated with the University of Nottingham and the Biotechnology and Biological Sciences Research Council (BBSRC) to research the mode of action of phosphite as a biostimulant.

The new EC fertilising product regulation EC 2019/1009, which was implemented in July 2022, is ground-breaking for our industry in that it includes Biostimulants as a category of its own. Yet, during the procedure that led to the approval of the regulation, phosphite was specifically excluded from the possible components of fertiliser products. We accept the position that phosphite has no direct nutritional value and that it is registered as an active ingredient under EC1107/2009 for plant protection products. However, as a substance with dual use potential in separate fertilising and plant protection products, it is not unique and should therefore not be excluded.

Our position is that phosphite has a scientifically proven mode of action and has been demonstrated over many years to be an effective biostimulant with an important agronomic input across a wide range of crops in European countries. Phosphite is now one of the most researched and consistently performing biostimulants on the market today and should continue to be accessible to growers in the future.

The PBSG is funded by its members and focuses on generating and communicating scientific evidence of phosphite’s efficacy as a biostimulant in order to retain its use for the benefit of European farmers. For more information on our work or to provide support for our aims, please contact us.

Technical Information

Phosphite, used as a biostimulant, encourages root development and improves nitrogen assimilation. It can be applied as a seed treatment or a foliar application and is readily absorbed and translocated to the roots.

Research has been undertaken by the University of Nottingham and Kiel University in Germany, using a systematic approach involving a combination of cell biology, plant physiology, biochemistry and X ray imaging techniques. Scientists have been working on two possible modes of action:

• cis-Zeatin hypothesis
  Phosphite increases production of the cytokinin cis-Zeatin (cZ), which improves the cZ/trans-Zeatin ratio. This leads to longer primary root growth, with more lateral extensions. It also reduces the translocation of phosphate from roots to shoots, further helping to enhance root growth.


• Nitrate reductase hypothesis
  Nitrate reductase (NR) catalyses a key step in assimilation of inorganic nitrogen into organic nitrogen. Researchers in University of Kiel have shown that phosphite treatment results in enhanced NR activity.