Managing soil acidity in intensively grazed dairy pastures

Page last updated: Wednesday, 17 January 2018 - 1:55pm

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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 a program to correct a soil acidity problem which had the potential to compromise the production of intensively grazed ryegrass pastures.

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 main messages for farmers from this part of the study were:

  • Soil test all paddocks to obtain pH values to assess if soil acidification is likely to be reducing pasture production.
  • If soil acidification is identified as a problem, start liming with as large levels of good quality lime as can be afforded until the desired pH is achieved.
  • Soil acidification is ameliorated by applying sufficient good quality lime to raise the pH of the top 10cm of soil, as measured in calcium chloride, to 5.5 or greater.
  • Where possible, lime should be incorporated into the soil after application to increase its effectiveness.
  • Soil acidification continues, both while liming and after liming has been successfully completed, particularly for intensively grazed pastures top-dressed with nitrogen after each grazing.
  • Once the target pH has been achieved, monitor soil pH and re-apply lime when pH declines below 5.5, requiring smaller amounts of lime (1t/ha) to return soil pH to 5.5 or greater.
  • Do not allow soil pH to decline much below 5.5 to avoid a major re-liming program to ameliorate the problem.