A compound comprising a water soluble salt of formula (I) wherein R1 is a C1-10alkyl group; or a C2-10alkenyl group; M is a cation of valency n, provided that when R1 is a pent-2-enyl group, Mn+ is other than sodium or potassium. These salts are particularly suitable for use in agricultural formulations. The formulations may further comprise benzoic acid derivatives and/or antioxidants.