The impact of the form and frequency of sulphur on pasture yield and composition in South Island high country

Abstract

Sulphur trials were carried out in the hill and high country of the South Island from 1986/87 to 2000/01. Initial trials showed that sulphur fortified superphosphate fertilisers are more effective products than fine elemental sulphur and sulphur bentonite prills, both in terms of dry matter production and cost effectiveness. This is because Sulphur Super products contain sulphate sulphur and finer elemental sulphur. Sulphur Super Extra (28% S) was more effective in the short to medium term than Maxi Sulphur Super (50% S) largely because it contained more sulphate sulphur. It would be a more preferable option for development, particularly when used at above maintenance rates. It is preferable to apply these products on a biennial rather than a triennial basis to maximise dry matter, maintain better sward composition and to improve the chances of coinciding application with better growth conditions, most notably summer rainfall. Residual elemental sulphur oxidises with time, reducing the dependence on biennial application, although there is still a risk of temporary sulphur deficiency and a delay in response of clover to follow up topdressing if topdressing is left beyond 2 years. Herbage sulphur levels, in conjunction with observation of pasture composition and vigour are useful to indicate when sulphur fertiliser needs to be reapplied. Keywords: sulphate sulphur, elemental sulphur, sulphur bentonite prills, wet mix Sulphur Super, Maxi Sulphur Super, anaerobic nitrogen