Agricultural activities are one of the major drivers of increased nutrient levels such as nitrogen (N) and phosphorus (P) to both terrestrial and aquatic ecosystems. Elevated nutrient concentrations are associated with degraded water quality that can result in potential impacts for human health and the environment. A recent European study has identified elevated concentrations of N and P for many European river monitoring stations. In many cases the management of N and P has been considered separately here we address the multi-dimensional issue of water quality where the simultaneous management and control of both N and P is considered desirable. Using an integrated modelling approach various nutrient management scenarios are examined. It is found that although the control of N and P involve different farm adjustments and induce different land use changes there is a certain degree of complementarity between these two nutrient controls. The policy implication of ignoring such complementarity is that the appropriate environmental taxes to control the required nutrient losses are overestimated, resulting in unnecessary welfare losses to the society.