Frank Brentrup1, Joachim Lammel1
1 Yara International, Research Centre Hanninghof, Hanninghof 35, 48249 Duelmen, Germany, www.yara.com, [email protected]
Several indicators are discussed to evaluate nitrogen use in agricultural production. Nitrogen use efficiency (NUE) can be defined as the ratio between N applied and N removed by the crop. NUE is, however, only one aspect of sustainability of N use. To account for environmental risks due to excess N, N balance (N input - N output) is seen as an appropriate indicator for N losses to the environment. While NUE and N balance focus on resource use efficiency and environmental pollution, the main purpose of agricultural production is providing food. It is therefore important to include the productivity dimension into the considerations, which can be crop N yield (crop yield * N content of the harvested product). The indicator system presented here considers these three important aspects of N use at the same time, i.e. resource use efficiency (NUE), environmental risk (N balance), and productivity (N output). All parameter can be derived from the same base data, N input and N output. Even more important as the way of calculation is the interpretation of the results. Examples from field trials show that very high as well as low NUE values may represent unsustainable systems and that the interpretation of NUE values requires a sound qualification scheme including acceptable boundaries for N balance and N output. This study explains (1) how the multi-dimensional indicator scheme works and how target values can be determined and (2) examines how agricultural practices such as precision farming tools support farmers achieving the defined targets.