Element balances as a tool for sustainable nutrient management: a critical appraisal of their merits and limitations within an agronomic and environmental context

Element balances are widely used and are incorporated within national action programs to combat nutrient emissions from agriculture to the environment. They rely on data that are readily available at farm-gate and field level, and the information generated is easy to communicate to farmers and policy makers. This may have contributed to high expectations on element balances as a tool for optimising agricultural nutrient use efficiency and thereby reducing nutrient losses. Element balances are potentially useful as a screening tool across Europe provided the methods to calculate them are standardised, their limitations and usefulness defined and appropriate target values are established by which they can be compared. It is difficult to establish straightforward relationships between nutrient management, surplus, losses and environmental impact. Simple farm-gate and field balances need to be complemented by a better understanding of the processes regulating nutrient dynamics, and their spatial and temporal variability. Hence, agronomic and environmental reference or target values need to be established for different production systems, geographical areas and elements. Proper instruments and tools as well as training and educational programmes have to be developed for a successful implementatio