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Aims Our goal was to assess how management and sward functional diversity affect nitrogen response efficiency (NRE), the ratio of plant biomass production to supply of available nitrogen (N) in temperate grassland. Methods A three-factorial design was employed: three sward compositions, two mowing frequencies, and two fertilization treatments. Results NRE was largely influenced by fertilization followed by mowing frequency and sward composition. NRE was larger in unfertilized than fertilized plots, in plots cut thrice than plots cut once per year, and in control swards than in monocot-or dicotenhanced swards. Fertilization decreased NRE through decreases in both N uptake efficiency (plant N uptake per supply of available N) and N use efficiency (NUE, biomass produced per plant N uptake) whereas mowing frequency and sward composition affected NRE through N uptake efficiency rather than NUE. The largest NRE in the control sward with 70 % monocots and 30 % dicots attests that these proportions of functional groups were best adapted in this grassland ecosystem. Conclusions Optimum NRE may not be a target of most farmers, but it is an appropriate tool to evaluate the consequences of grassland management practices, which farmers may employ to maximize profit, on environmental quality.

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Grasslands play an important role in land use, covering one third of the agriculturally utilized landscape in Europe. As a consequence of management intensification in the last 60 years, the productivity of grasslands increased and the diversity of these systems decreased.Nitrogen (N) plays a key role in these ecosystemsit limits primary productivity and affects biodiversity. Increasing N supply may alter nitrous oxide (N 2 O) and nitric oxide (NO) emissions, which play a major role in atmospheric chemistry and contribute to global warming. Nitrate