Precision Soil Mapping on Central Victorian Pastures trial update


Todd Buck

Local growers gathered near Ascot recently to obtain an update on the “Precision Soil Mapping on Central Victorian Pastures” Producer Demonstration Site and participate in a hands-on workshop on phosphorus management.

Precision Soil Mapping in Central Victorian Pastures is a Meat and Livestock Australia (MLA) funded collaboration between the Smeaton and Pyrenees BestWool BestLamb groups, Agriculture Victoria, and Precision Agriculture Pty Ltd. The project investigates the economic benefits of variable rate applications (VRA) and soil mapping on four demonstration sites spread across Central Victoria.

Attendees started the afternoon with a visit to one of the demonstration sites situated on Bruce Spittles property, where variable rate lime and gypsum were spread in early 2021. Variable rate technology was used to spread higher rates on more acidic or sodic areas, whilst backing off rates in better areas – in theory providing more effective and efficient soil amelioration. These inputs were targeted by soil sampling the paddocks in a grid to provide spatial maps of soil conditions and nutrition. Variable rate paddocks are monitored alongside more conventionally managed paddocks to measure how the approach has affected pasture production and the bottom line.

“Grid soil sampling revealed variability in a range of nutrients and soil characteristics across each of the demonstration sites,” according to Precision Agriculture’s Georgie Rees. “Although it’s too early in the project for us to draw any meaningful conclusions, variable rate sites have so far tended towards higher grazing days and improved pasture compositions, but with no apparent difference in biomass or quality cuts.”

Subsoil sampling also revealed increases in soil acidity down the soil profile on some paddocks that reflected a history of surface-applied lime, making it important for growers to monitor conditions in their subsoil and adjust management accordingly.

Following a quick lesson in the use of the MLA Pasture Ruler from group facilitator Neil James (Agriculture Victoria), Dr. Kirsten Barlow guided attendees through the use of MLA’s Soil Phosphorus Tool. This free resource uses five easy steps to ensure that growers are making money from phosphorus fertiliser by matching their applications to plant and animal requirements.

The Precision Soil Mapping in Central Victorian Pastures project continues until late 2024, with a thorough economic analysis that will help to answer questions about the benefits of variable rate applications. 

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