Fertiliser sulphur for intensively grazed dairy pastures

Page last updated: Wednesday, 17 January 2018 - 1:40pm

Please note: This content may be out of date and is currently under review.

The Greener Pastures project was set up to assist the Australian dairy industry meet the two major challenges in managing high performing pasture systems: maintaining profitability while meeting the expectations of a community that is increasingly sensitive to environmental issues. This page discusses the major findings from studies to better define the sulphur requirements of intensively grazed ryegrass pastures.

Introduction 

This report is based on annual soil testing over 10 years of 48 dairy paddocks at Vasse Research Centre in the south-west of Western Australia.

The same critical KCl-40 soil test value — about 6.5mg/kg — has been determined for pastures throughout Australia receiving greater than about 560mm annual average rainfall. In this study, soil test values were always above 6.0mg/kg.

Because sulphur mineralised from soil organic matter or dissolved from applied fertiliser can be leached, soil testing for sulphur cannot be used to confidently determine the fertiliser sulphur requirements of high rainfall pastures in the next growing season. As the extent of leaching of sulphur cannot be predicted, the recommendation for these pastures is to always apply fertiliser sulphur after July each year — after the peak of the winter-wet growing season. Tissue testing should be used to assess and improve sulphur management.

The main messages for farmers from the study were:

For intensively grazed ryegrass-dominant pastures

  • Apply fertiliser sulphur and nitrogen after each grazing
  • Applying 5–7kg S/ha after each grazing supplied sufficient sulphur for ryegrass dry matter production.

For traditional clover-ryegrass pastures which are not top-dressed with fertiliser nitrogen after each grazing but instead rely on clover as the main source of nitrogen for pasture production

  • Apply fertiliser sulphur after July each year to supply 25–50kg S/ha