Forage quality and yield increments of intensive managed grassland in response to combined sulphur-nitrogen fertilization Dedicated to Prof. em.Dr. Alois Kornher on his 75th birthday.

A three-year experiment was carried out at three different sites in northern Germany to investigate the effects of combined sulphur (S, up to 50 kg S ha−1 year−1) and nitrogen (N, up to 300 kg N ha−1 year−1) fertilization on dry matter (DM) yield and forage quality. There was an interaction effect of site, year, S and N fertilization. The greatest DM yield increment relative to yield at the start of the experiment (1997) with no S and N applied was 10.2 t DM ha−1 at Ostenfeld (arable grassland). Cattle slurry when applied to provide 50 kg N ha−1 and 10 kg S ha−1 did not noticeably increase yield. The S content in forage decreased significantly over the years without S fertilization. At 300 kg N ha−1 and 0 kg S ha−1, crude protein (CP) contents achieved 173 g kg−1 DM and were diluted due to higher DM yields with S fertilization. The true protein content (TP% of CP) differed significantly at 300 kg N ha−1. TP achieved 93% with 50 and 87% with 0 kg S ha−1 year−1, respectively. In conclusion, with N fertilizer intensities in the range of 300 kg N ha−1, it is necessary to apply 25 kg S ha−1 to improve forage yield and quality. On the other hand, with N fertilization levels below 300 kg N ha−1, S fertilization could be omitted.