Acid soils in the Upper South East: it’s time to lime

Dr Melissa Fraser, Claire Dennerley, Project Team: Daniel Newson, Brian Hughes, PIRSA Rural Solutions SA, Natural Resources South East (NRSE) - MacKillop Farm Management Group

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

Lime treats soil acidity by neutralising the acid reaction in soils and is the only cost effective way to manage acidic soil; it is most effectively applied to prevent acidification in the first instance. Farmers should discuss soil pH and lime requirements with their agronomist

What is the problem?

The damaging effects and substantial cost of acidity have come back on the radar in recent years thanks to a number of GRDC and National Landcare projects that have been delivered throughout Southern Australia. Liming soils was regular management practice across the South East in the 1980s, but it has dropped off of the soil amendment program of many farmers over the last few decades.

The objective of the project was to work with landholders in the region to increase their capacity and knowledge to productively and sustainably manage their soil by developing a snapshot of the extent of acidity on their properties

What did the research involve?

An initial workshop was held with 10 participating landholders in August 2017 where an overview of soil acidity was presented, including the process of acidification, causes, impacts and amelioration techniques.

A final workshop in December 2017 provided each landholder with a report on the extent and degree of acidity across their paddock/s. Tools for managing soil acidity were presented, including the ‘Maintenance Lime Rate’ calculator and ‘Lime Cheque”

What were the key findings?

  • Acidity was found to be more widespread in the USE than expected, with 15 of the 18 paddocks examined containing zones of soil with pH below 5.5
  • Sandy loam and clay soils used for cropping were acidic
  • Clay spread shallow sandy soils used for cropping were acidic
  • Clay spread deep sandy soils used for grazing were acidic
  • The target soil pHCa range is between 5.5 and 6.5; lime needs to be applied now to combat current and future acidification.

Results from this project have shown acidity to be prevalent on sandy soils in the Upper SE of SA, particularly those used for regular cropping; they also showed the neutralising effects of clay spreading and delving to be relatively short lived.

Final comment

Lime is an essential soil amendment required in these systems.

Multiple decision support tools are available at https://agex.org.au/project/soil-acidity/ to aid the identification of acid prone farming systems and also to determine the rates of lime required to overcome acidity.

2018 - Australia - Dr Melissa Fraser, Claire Dennerley, Project Team: Daniel Newson, Brian Hughes, PIRSA Rural Solutions SA, Natural Resources South East (NRSE) - MacKillop Farm Management Group
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