This paper describes the development of a new and efficient agri-environmental measure, gypsum amendment of arable fields, and its inclusion as a voluntary measure in national agricultural support schemes. Gypsum reduces erosion and both particulate and dissolved reactive phosphorous loads to surface waters, thus having high potential in the Finnish agriculture in contributing Finland to meet phosphorous reduction targets set by the HELCOM Baltic Sea Action Plan. Gypsum amendment suits clayey soils located also in other Baltic Sea countries. A large scale gypsum pilot was organized in Southwest Finland, along the Savijoki River that flows to the Baltic Sea. Structured surveys and discussions in workshop explored how 55 farmers adopted gypsum amendment and gathered experience from spreading gypsum and its impacts on soils, yields and aquatic systems. Gypsum amendment is an investment in nutrient load reduction that entails high upfront costs to farmers and requiring, in case of large farms, a public tendering. As these may hinder large-scale adoption of an efficient measure, the paper suggests to include a completely new option to CAP framework: national environmental protection investments that facilitate ex-ante payment schemes to overcome the financial challenge to farmers.