The sulphur status of intensive grassland sites in southern Scotland

Field trials were carried out at five sites in southern Scotland to examine the sulphur status of intensively grown grass under varying Inputs of atmospheric and rainfall sulphur. Sulphur budgets were prepared by comparing amounts of sulphur removed at harvest with sulphur inputs from rainfall, the atmosphere and fertilizers.
No yield responses to added sulphur were obtained, although soil-derived sulphur was essential for the maintenance of optimal sulphur levels in herbage. Where no fertilizer sulphur was added, mineralization of soil organic sulphur supplied approximately 8 to 18 kg S ha^-1 annually during the growing season. Maintenance requirements of 5 to 10 kg S ha^-1 annually were indicated at the Dumfriesshire and Midlothian sites and 20 kg S ha^-1 annually at the Berwickshire sites to prevent a decline in soil sulphur reserves. Total sulphur concentrations of less than 2 g S kg^-1 dry matter were observed in herbage at some samplings indicating marginal sulphur sufficiency. Sulphate levels in herbage, expressed as a percentage of total sulphur, also indicated that sulphur supplies barely matched crop requirements.