Controlling Extreme Weeds After Extreme Events

Summary

​The aim of this Producer Demonstration Site (PDS) is to demonstrate to what extent improved weed control and follow-up management (eg: grazing, fertilizer or additional chemical control) improves both persistence and productivity of newly sown or degraded permanent pastures in fire affected areas. 

Objectives

By December 2025, in the Upper Murray and East Gippsland regions of Victoria the consultant and producer group will have:

1. 90% of core and 45% of observer group members more confident in identifying key pasture and weed species by;

   • Weed and pasture identification field day (late Autumn 2022)

   • Pasture assessment tools to estimate weed percentages and pasture composition

2. Assessment of appropriate interventions and control strategies

   • Autumn weed identification and control recommendations field day, and these recommendations implemented, on a host farm in each region (June 2022)

   • Development of long term weed control strategies for the 4 host farms.

3. Implement up to four different weed control strategies on newly sown pastures at demonstration host farms using a combination of approaches that include; chemicals, fertiliser and tactical rest periods, that result in a 20% higher desirable plant species by Spring 2025 (three years after sowing).

   • Undertake pasture benchmarking to establish priority weeds.

   • Implementation of individual weed control programs on host farms.

4. Implement two different weed control strategies on demonstration host farms, in consultation with lead agronomist, that result in a 10% improvement in desirable species in previously degraded but not resown pastures by Spring 2025.

5. Achieve a 50% increase in the number of observer producers of the two regions doing annual assessments of key weed species and a winter assessment of pasture composition across key paddocks by 2025.

6. 90% of core producers and 40% of observer produces indicate they have adopted or intend to adopt at least one of the weed control management practices implemented at one of the demonstration farms into their own property.

Progress

This Producer Demonstration Site (PDS) project, delivered from 2022 – 2025, demonstrated how improved weed control and follow-up management can accelerate recovery and lift productivity of bushfire-affected pastures in the Upper Murray and East Gippsland, Victoria. A paired paddock approach (Normal Farm Practice [NFP – Control] and Normal Farm Practice Plus [NFP+ – Treatment]) was used with monitoring including pasture composition, feed quality, soil fertility and (where possible) stocking rates. 

The demonstration showed that previously burnt out pastures can be returned to productive systems, with a reduction in weed burden.  Across sites, targeted chemical control and follow-up management demonstrated improved pasture compositions and productivity. At the Upper Murray site, management changes demonstrated clear productivity gains, with strip grazing improving pasture utilisation and enabling higher stocking rates (e.g. 16.8 DSE/ha compared with 9.4 DSE/ha on areas with similar pasture composition and fertility). Urea test strips demonstrated that earlier nitrogen applications (once soil moisture was no longer limiting) produced the strongest winter–spring feed response and provided a low-cost way to identify and address key production constraints.  

In East Gippsland, the Ensay site demonstrated the value of using short-term fodder crops as a ‘cleaning’ phase to reduce annual grass pressure (supported by herbicide and fertiliser applications), while providing useful short-term feed during the renovation period. At the Clifton Creek site (existing pasture), combining soil fertility correction (lime and fertiliser guided by soil tests) with targeted control of Chilean needle grass and follow-up pasture management demonstrated a shift toward more desirable species: desirable grasses increased to 56% in NFP+ compared with 19% in the NFP, while weed grasses reduced to ~3% in NFP+ compared with ~32% in the NFP. 

Overall, the project demonstrated to producers practical, local case studies that support producer decision-making after fire (and other extreme events such as drought), and highlight the importance of timely weed control, soil fertility management and ongoing monitoring to underpin pasture persistence and productivity. By demonstrating a range of management strategies with a highly visual, ‘hands-on’ approach. the project increased producer confidence in applying targeted weed control, fertiliser and grazing strategies to accelerate pasture recovery under commercial conditions.

This project was designed to demonstrate practical management options under commercial conditions rather than produce statistically controlled research outcomes.