NGN - Understanding herbicide residues on challenging soil types within the southern region

National Grower Network forums throughout South Australia have identified that herbicide residues are a concern for growers. From work conducted by Rose et al., (2022), it is estimated that between 20-30% of paddocks across Australia contain soil-bourne herbicide residues that constrain crop selection, and 10% of paddocks have residues that could result in crop damage and economic losses to growers. Whilst the mechanisms and drivers of herbicide breakdown are relatively well known, there is a lack of decision support to predict the level of herbicide remaining in the soil and the risk to crops, especially on challenging and uncommon soil types.

To address this, GRDC is investing in a program of work that will support grower and adviser understanding of how herbicides interact with their soil types to assist their pre-sowing decisions on the crop types or varieties to be planted. This information can also assist growers to make informed decisions about in crop and pre-emergent chemistry applications to avoid plant back issues.

This investment will help supplement a larger existing national investment (DPI2306-013RTX) examining the spatial variability of soil types and how this impacts herbicide breakdown and residues. It will strengthen the existing work through the inclusion of unique and less common soil types in SA, including the regions around Wirrulla, Wangary, Jamestown, Balaklava, Warooka and Bowhill, through developing dose response curves and conducting paddock surveys.

Support available from Analytics for the Australian Grains Industry (AAGI)

GRDC's strategic AAGI partnership can offer the following analytics support as a GRDC in-kind contribution: advice on design of validation and dose-response trials, and statistical support for development of dose-response curves. To access this support, applicants must enquire with AAGI directly and describe the proposed support scope in their tender. The tender should include an estimate of workload and in-kind valuation provided by AAGI. Please make enquiries to Adelaide University at [email hidden] (attention Dr Julian Taylor). Successful applicants will be required to complete an Analytical Collaboration Plan to specify the data to be provided to AAGI and the analytics support AAGI will provide. A sample Plan template is available from AAGI. Please note, applicants that decline AAGI support must provide a technical and value-for-money rationale for not using in-kind AAGI support.

Outcome:

By May 2027, 30% of growers and advisers with calcareous and alkaline soil types in SA have improved understanding of herbicide behaviour in their soils and confidence to make informed variety and cop type selections considering herbicide residues.

Outputs:

Output 1.

Title: Delivery and analysis of herbicide residue dose response curves.

Description:

By May 2027, deliver a report detailing herbicide residue curves for six soil types within the southern region where there is low grower confidence in plant back times and where the issue has been raised at NGN fora.

Dose response curves will be determined for different soil types through glasshouse studies and supported through paddock surveys in the regions with challenging residue levels. This will include:

· Dose response curves for up to two herbicides per soil type, with two crop types of concern per herbicide.

· Choice of herbicide and crop types for dose response curves will be developed with support from local agronomists, growers and farming systems groups to ensure local relevancy.

· Results and protocols will leverage DPI2306-013RTX to ensure these data are compatible with the national investment on spatial variability.

· GRDC’s strategic partnership, Analytics for the Australian Grains Industry (AAGI), can support paddock data analysis and profitability benchmarking analytics as a GRDC in-kind contribution. To access this support, applicants must negotiate with AAGI directly and describe the agreed support scope and arrangements in their tender.

Output 2.

Title: Extension and communication activities.

Description:

By May 2027, deliver extension and communication activities targeted at growers and advisers to increase understanding of herbicide residues, primarily on calcareous soil types within the southern region.

· A communication and extension (C&E) plan will be developed as part of the Annual Operating Plan for each year of the trials and will include consideration of GRDC avenues for promotion and extension of the work, including, but are not limited to, GRDC electronic mail to the CRM (event promotion), GroundCover, GRDC Grains research Updates, GRDC webinars, GRDC podcasts and video channels, social media.

· Key results and conclusions will be published through local grower groups, and other GRDC media channels.

· Extension activities may include but are not limited to demonstrations, trial strips and local discussion groups. Consider other extension activities including development of case studies for each of the regions. It is expected there will be at least six extension activities, one in each of the regions of focus.

· Final reporting should include implications of results and recommendations for further investment and extension activities. An assessment of project impact on grower attitudes toward herbicide residues and crop choice selection should also be included.