A discussion of norms for S supply in organic farming based on content in forage and ruminant performance in Norway

Summary

The content of sulphur (S) in grassland on 27 Norwegian organic farms with dairy or sheep production was investigated in 2001 and 2002. The forage content of S was below the norms (2 g S kg DM-1) for both plants and animals in a large proportion of the samples. The average S content in forage at dairy farms was 1.4 g S kg DM-1 and at sheep farms 1.5 g. Even on grasslands with low plant S content (<1 g S kg DM-1), S-fertilization did not increase yields and increased the plants’ S content only very slightly. No indications of S deficiency were observed on the dairy farms. For one sheep farm with a forage S content of 1.1 ± 0.1g S kg DM-1, brittle and short winter wool was reported.