Assessment of N and P status at the landscape scale using environmental models and measurements

We assessed the compliance of a Dutch landscape, dominated by dairy farming, with environmental quality standards using a combination of model calculations and measurements. The total ammonia emission of 2.4 kton NH(3) yr(-1) does not exceed the environmental quality standard (2.6 kton NH(3) yr(-1)). Nevertheless, the total N deposition (on average 24.4 kg N ha(-1) yr(-1)) is such that critical N loads are exceeded at 53% of the nature areas. The deposited N mainly results from non-agricultural sources and agricultural sources outside the area (72%). The calculated average NO(3)(-) concentration in the upper groundwater does not exceed the 50 mg l(-1) threshold. Calculated annual average N-total and P-total concentrations in discharge water are relatively high but these cannot be directly compared with thresholds for surface water. The results suggest that compliance monitoring at the landscape scale needs to include source indicators and cannot be based on state indicators alone.