Discing in lime at Stawell 20190301 084757

Innovative approaches to managing subsoil acidity

Many growers know the benefits of liming soils prior to sowing based on their soil pH levels, but many do not know of the various different ways to apply lime especially when it comes to ameliorating subsoil acidity. The GRDC funded ‘Innovative approaches to managing subsoil acidity in the southern grain region’ project is currently in its final reporting phase after testing different lime applications, including an organic amendment application. The objective of the project is to increase farmer awareness of subsoil acidity while demonstrating the effectiveness of innovative technologies on a farm scale.

Two trial sites were established in 2018 and 2019 in the Rokewood and Stawell regions.  Both sites were soil tested at establishment with very acidic pH levels in the top 30cm with pH(CaCl2) ranging from 4.2 to 5.3. With observations and grain yield results collected for the 2019 and 2020 growing seasons.

Five treatments including a control (nil application) were set up in 100m long strips.

The treatments consisted of:

  1. Surface lime – incorporated into the top 10 cm of soil
  2. Deep ripping – ripping depth of 30cm, 50cm wide after a surface lime application
  3. Deep ripping and surface lime – surface applied lime deep ripped to a 30cm depth, 50cm wide, with deep liming at 10-30cm applied with a target pH of 5.0
  4. Deep ripped organic amendment – surface liming ripped to a depth of 30cm, 50cm wide, with lucerne pellets placed at 10-30cm at a rate of 15t/ha
  5. No Treatment

All treatments had a pH target of 5.5 with exception of treatment 3 the deep liming treatment, which has a subsoil target of 5.0.

In the 2020 growing season, visual differences were observed in the Oat crop at Stawell. Treatment 4 the deep ripped organic amendment had thicker and taller crop growth when compared to the other treatments and control plots. The Canola crop at the Rokewood site did not appear to have any visual differences observed during the season. The final soil testing has occurred recently, with samples analysed by NSW DPI for soil pH, exchangeable cations, nutrients and soil organic carbon.

The final soil test results and project findings will be available in the final report soon. For more information about the project, contact Tahlia at tbruce@sfs.org.au or Lisa Miller at lmiller@sfs.org.au

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