With the growing availability of commercial precision agriculture (PA) data collection services and variable rate (VR) application technologies, an increasing number of producers within the FarmLink region are adopting site-specific soil amelioration practices for lime and gypsum inputs.
This project examines the ability of a number of data collection methods including EM38, grid soil sampling and strategic segmented sampling to quantify horizontal and vertical spatial variability of soil constraints including soil acidity and dispersiveness within a pilot/test paddock located at Ardlethan, NSW.
- Identification of a highly stratified pH profile and subsurface acidity layer at this location (medium rainfall zone) suggests this problem may be more widespread than previously thought
- Topsoil (0-10cm) grid soil pH mapping in isolation would not have identified the subsurface acidity problem in this example and the result most likely would have been under-liming
- Subsurface acidity (10-20cm) varied within the paddock and was more severe (lower pH and deeper) in soils of lower buffering capacities, e. lower Cation Exchange Capacity (CEC)
- Both apparent electrical conductivity (ECa) measured via EM38 and topsoil (0-10cm) grid CEC soil mapping correlated well with subsurface pH, indicating either data layer would be suitable to use to design strategic 5cm segmented pH Further work is required to determine if this relationship extends to different management practices, soil types and liming histories
- Both ECa and 0-10cm grid soil CEC/Exchangeable Sodium Percentage (ESP) mapping broadly correlated with sodium concentrations at depth, as well as dispersiveness as measured by Emerson’s tests; indicating either data collection method could be used for site-specific gypsum applications in this example
- Quantifying and treating multiple soil constraints on a site-specific basis is complex. Investing in a one-off higher resolution ECa data layer (e.g. EM38 survey) and deep ground-truth soil sampling before commencing variable rate practices has merit
- Advances in the following would be advantageous for progressing site-specific amelioration practices:
- Liming calculators/decision support tools that can model the effect of liming rate, treatment depth, incorporation practices, productivity and average annual rainfall on a site-specific basis
- Analysis methods to directly quantify soil dispersiveness as well as associated ameliorant calculators
Recently Eva presented a webinar to the Precision Ag CoP on this research – please view the below video
Read the full research report here @ Research Report
Farmlink Research @ http://www.farmlink.com.au/
Precision Agriculture Pty Ltd @ https://www.precisionagriculture.com.au/