A regulator who wishes to mitigate non-point source pollution and maintain the farmers’ revenue can choose among several policy tools. This paper compares the expected effects of several instruments on the pollution and profit levels, taking into account their acceptability : linear taxation of fertilisers, uniform extensification, fertiliser;quota. We focus on the interest of designing regulation mechanisms based on a nonlinear taxation of the production. The empirical results concern a watershed in the western part of France.