Precision soil mapping in Central Victorian Pastures

Summary

This Producer Demonstration Site (PDS) is designed to support adoption of precision soil testing on variable grazing paddocks in central Victoria, and demonstrate the related production, economic and environmental benefits of variable rate fertilizer applications.

Objectives

By 2024:

1. Demonstrate increased productivity that results from more precise soil and fertiliser management (PA) on four grazing properties in central Victoria.

   (a) Map the level of soil variability in pH, P, K, exchangeable cations and sulphur across paired paddocks on four host producer farms (PA treatment), and provide a comparison to the results of conventional soil testing approaches.

   (b) Undertake variable rate applications (VRA) of appropriate fertilizer/ameliorants on PA treatment paddocks according to mapped results, and continue uniform fertiliser applications on control paddocks according to the usual producer practices at each site.

   (c) Improve application efficiency across 70% of each VRA demonstration paddock, compared to a conventional uniform rate.

   (d) Measure production (livestock and pasture) differences associated with the mapped variability and the VRA practice.

2. Increase producer knowledge and skills of soil health and fertility, pasture growth rates and measurements and Precision Ag practices for 80% of participating producers.

3. Deliver a cost benefit analysis for each site comparing PA practices with existing soil testing and fertiliser practices.

4. Showcase the demonstration sites via two paddock walks/ inspections with groups each year and three combined group field days over the life of the project. Ongoing adoption of improved soil management practices (including more intensive soil sampling and VRA) is anticipated for 70% of core producers and across an additional 9,000ha for observer producers.

Progress

Variability in soil characteristics, such as acidity and the nutrients critical to pasture growth, can be substantial within a single paddock due to the ongoing influence of soil types, management decisions and livestock movement. Variable Rate Applications (VRA) are commonly used in cropping to provide better targeting of fertiliser and ameliorants, but uptake is low in the livestock industry. This Producer Demonstration Site (PDS) was established in late 2020 at four properties owned by members of the Smeaton and Pyrenees BestWool/BestLamb (BWBL) groups in Victoria. At each site, paired paddocks representative of soil types and pasture species were grid soil-sampled to map the variability in soil characteristics. One of each pair received VRA of fertiliser/ameliorants (treatment) and the other a conventional uniform rate based on averaged soil test results and calculated by the producer group (control). Both the VRA and control (phosphorus and potassium) were affected by nutrient redistribution in the paddock by livestock movement. Initial pH variability was relatively low in some of the paddocks requiring lime and the VRA and control applications brought about similar improvements to pH. The ‘rule of thumb’ application of 2.5t/ha gypsum to the control was more than required and the target (<6% Exchangeable Sodium Percentage (ESP)) was exceeded, highlighting the need to calculate requirements rather than just using a rule of thumb and the importance of regular soil testing.