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Soil Acidity Issues and Insights from PA Platform – Soli

The Government of South Australia’s Department for Environment and Water recently published the Current and Potential Soil Acidity Map (see above).  The report estimates about 1.8 million hectares (20%) of cropping land in South Australia (SA) currently have surface soil acidity (0-10cm < pHCaCl2 5.5) or is considered acid prone, and this area is expected to double over the next 40 years if remedial action is not taken.

As detailed in the report, the consequences of untreated highly acid soils include:

  • loss of production and financial returns, particularly for acid-sensitive plants (e.g. Lucerne and pulses)
  • progressive acidification of subsurface and subsoil layers, which are much more complex and costly to ameliorate
  • At a low soil pH, microbial activity declines and nutrients such as phosphorus, magnesium, calcium, and molybdenum become less available
  • When pH falls below 5.0 (CaCl2 ), toxic amounts of aluminium and manganese can be released into the soil solution.
  • reduced uptake of soil water that can lead to rising water tables and increased soil salinity
  • increased leaching of iron, aluminum, and some other nutrients from the soil, potentially contaminating surface and groundwater

These maps are invaluable in highlighting the extent of soil acidity and can challenge previously held views about what is happening in our backyard. For example,

  • the map clearly shows issues on the East side of the Yorke Peninsula which in our experience was not previously seen as having acidity issues
  • it also highlights areas where growers are aware of acidity issues e.g. Kangaroo Island and have been addressing this over several years.

Combined Current And Future Acidity

Similar maps are available in each state (click the state to view) – NSW / VIC

PA Data from our Data and Insights Platform

  • Using our data and insights platform – Soli – we have reviewed 350 datasets of growers who have returned to test their pH levels using PA’s nutrient mapping and grid sampling services approximately 3 years after VR Lime applications.
  • From this data, we can see on average an increase in pH across more than 17,000ha with an average of 0.22 pH units, however, the change is dependent on the initial pH distribution, ranging from 0.71 pH unit increase where the initial pH was less than 4.6, to a 0.27 pH unit decline in pH where the initial pH was greater than 6 and no lime was applied.
The above chart shows the average change in pH observed over 3+ years, grouped by the initial pH measured in initial sampling.
The above graphic shows the initial pH (cacl) results in the paddocks.
Pink represents <4.5, Red 4.5-4.8, Yellow 4.8-5.2, Light Green 5.2-5.8
The above graphic shows the pH (cacl) results in the paddocks after retesting around 3 years after the initial testing and VR application of Lime. Yellow 4.8-5.2, Light green 5.2-5.8, and Blue represent 5.8+

Precision Agriculture (PA) provides surface nutrient mapping and targeted sub-surface sampling across Eastern Australia to assist growers and agronomists to develop programs to address acidity issues. This data is processed in PA’s proprietary platform, providing PA customers with insights from large, anonymised datasets.

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