Nitrogen indicators for characterizing farm performance in European case studies

Nitrogen (N) indicators such as N use efficiency, N surplus and N output based on farm-gate balances are key for evaluating farm performance. In this study, a common protocol was used for calculating N indicators of 1240 farms from six European countries. The goal was to characterize farm performance for the different typologies and derive possible target values. Nitrogen indicators were useful to characterize farming systems, but caution is needed when comparing livestock farms before correcting for N losses involved in the production of purchased feed and the end use of exported manure.

Understanding differences in N indicators at the farm scale is crucial for monitoring food production and environmental sustainability. Our objective was to characterize farm N performance for the different farm typologies and derive possible target values.

The guidance document developed by the European N Expert Panel was used for calculating N indicators of 1240 farms from six European countries (EUNEP, 2016). Nitrogen balances registered the inputs and outputs at the farm-gate and were reported as kg N ha-1 year-1 . Nitrogen use efficiency (NUE = Noutputs/Ninputs) and N surplus (Noutputs-Ninputs) were calculated for each farm. A characteristic operating space for each farm type was identified based on the statistical analysis of the farm population, and target values were proposed as references for improving farm performance (Quemada et al., 2020). To account for externalization of N losses involved in production of purchased feed and use of exported manure, N inputs were recalculated with adjusting factors.