Redesign of broadacre farming systems of SE Australia

WHY THIS PROJECT IS IMPORTANT

In Australia, drought and heat events have challenged the resilience and profitability of farming businesses. Climate-related production risks require a more resilient farming approach to sustain farm productivity. Diverse farming options can make current farms more efficient and resilient and on-farm diversification can be a promising strategy for farming communities to cope with and recover from stresses like drought.

This project is investigating the role of legumes, dual-purpose wheat, silicon applications, and native corridors on-farm. The effect of these practices on resilience against climate challenges and droughts will be evaluated and quantified. 

Northern Victoria is a region identified by ABARES (2020) as one of four regions in Australia at the highest level of drought risk nationally. Because of the propensity to drought, broadacre farming systems across south-eastern Australia and other regions of Australia require changes to remain productive and profitable when exposed to increasing risks from more frequent droughts.

This project is part of a larger project which aims to help the agricultural industry plan for, cope with, and recover from drought.

Project focus

Riverine Plains is contributing to all key areas of research for the broader project. This includes the role of legumes in the crop rotation, diversified production options through dual-purpose wheat for grazing and grain production, drought stress mitigation through silicon applications, and comparison of native corridors to non-farmed areas which lack vegetation.

This will help provide evidence-based innovative research for diversified farms in south-eastern Australian. It will also allow farmers in the Riverine Plains region to consider options outside of the typical inputs to build resilience to more frequent droughts under climate challenges.

Dual-purpose wheat for graze and grain

Managing the green feed sources for livestock during the early winter period can be challenging. Organised grazing of dual-purpose wheat crops at a specific growth stage can provide fresh biomass for grazing during wintertime. Using micronutrient foliar applications may help the crop recover and minimise the yield penalty at harvest.

Silicon application sustains crop yield under drought stress

Silicon is a micronutrient with a versatile role and provides many benefits for plant growth, specifically under stresses like drought and heat. Silicon enhances photosynthesis, plant growth, yield and crop quality and also improves water relations. Addition of silicon-containing fertilisers has also been shown to have a positive effect on grain quality by improving its nutritional profile.

Riverine Plains, along with other project partner organisations and sites, is investigating the use of silicon in broadacre cropping systems through the applications of a commercially available silicon-containing fertiliser as a foliar spray, across replicated and demonstration trials.

Native corridors

The use of native corridors near productive cropping paddocks is also being investigated by Riverine Plains. This project component involves baseline soil testing and plant identification to better understand the role of native plants in our farming systems.

Analysis

A cost-benefit analysis of various practices and treatments across the sites will be conducted, while soil, plant, and grazing measurements will provide quantifiable metrics. Each farming system will also be evaluated through an innovative ‘Drought resilience and risk index/indicator’ to quantify drought resilience and risk reduction.

Project Outcomes

Silicon fertiliser for drought resilience in broadacre cropping 

Key points

• When applied in drought-stress trials, silicon (Si) has demonstrated increased photosynthetic activity of the plant and improved water relations, leading to improved crop yield.
•  Silicon fertiliser application did not show any significant differences in biomass and grain yield of the evaluated crops during 2022. The season’s climate must be considered when interpreting this result, as it was not a typical season where crops faced periods of moisture or heat stress.
• Visual effects of stay-green phenotype (prolonged green foliage) were observed in wheat plots later in the season, indicating silicon's beneficial effects.

Background

In Australia, drought and heat events have challenged the resilience and profitability of farming businesses. Climate change requires a more resilient farming approach to sustain farm productivity. Diversified farming options can make existing farms more resilient and profitable in changing climate scenarios. On-farm diversification can be a promising strategy for farming communities to cope with and recover from stresses like drought.

The parent project, Whole-system redesign of broadacre farming of southeast Australia, aims to help the agricultural industry to cope with, and recover from drought. One of the main drought mitigation strategies being trialed is the use of silicon fertiliser in broadacre systems. The project also demonstrates overall farm diversity enhancement with the inclusion of native vegetation cover on non-farming areas of the farm.

Aim

To provide evidence-based, innovative research for diversified farms in south-eastern Australia. The projects aims are:

1. To demonstrate the potential role of legumes incorporation in the wheat/canola monocropping system
2. Further consider the option of dual-purpose wheat (grain and graze option) cultivars in the Riverine Plains region
3. To showcase cost effective drought mitigation strategy to the farming community, i.e., foliar application of Si
4. To consider the health of cropping ecosystem, integration of native vegetation on the farmland to diversify farms income.
   

Table 1  Site details

Method

Eight plots were sown to each crop type in a paddock within the Riverine Plains region. Crop types included faba beans, spring wheat, dual-purpose winter wheat, and canola. The treatments were control (no silicon) and foliar silicon application, with four replicates per treatment. Before sowing, 12 soil cores were taken across site, segmented into 0-10cm and 10-20cm , with the pre- sowing soil chemical analysis presented in Table 2. A demonstration site for faba beans was also included as a part of this project. This site was managed within a farmer’s paddock and silicon fertiliser spray was applied to half of the selected area. The commercially available silicon fertiliser was applied at the rate of 300ml/ha, with a water rate of 400L/ha, five times throughout the season. The first application was in mid-August, GS30 in wheat, with the consecutive sprays being applied 10-14 days after the previous.

A native corridor assessment by expert Meredith Mitchell and FDF project staff identified plants and marked them for continuous monitoring.

Three different types of native grasses were identified in the Riverine Plains native corridor. To understand the impact of these native grasses on the soil microbial community composition, diversity and their role in shaping the soil health for sustainable crop production, soil samples will be taken throughout the length of the project.

Grazing wheat plots had half the plot area mown to represent grazing at GS25. The biomass cuts were taken for all wheat plots at GS33 and again at GS65. Approximately 2.7m² of the grazed area of the plot was sprayed with silicon fertiliser and 1 L/ha of micronutrient formulation in mid-October to enhance crop re-growth after a grazing period. Final biomass cuts and harvest index calculations were taken on this portion of the plot to compare with the unsprayed control grazed area.

Harvest index was calculated at crop maturity. Plots were harvested for grain yield and sub- samples were taken to test protein and nutrient content. The dual-purpose wheat plots were harvested separately, the grazed and non-grazed areas.

Table 2  Pre-sowing soil chemical properties

Results and discussion

Site details and soil data are shown in Tables 1 and 2. Post-harvest soil test data are at analysis stage, and not included in this report. Due to excessive rainfall, all canola replicates were not taken through to harvest at the Uncle Tobys site. Faba bean replicated plots were maintained near our demonstration site in Bundalong South due to poor establishment at the Uncle Tobys site.

The faba bean replicated trial did not receive all anticipated silicon sprays due to unexpected rains and a road closure due to flooding, therefore the results are not included in this report.

Tables 3 to 5 show biomass, harvest index, plot yield and grain traits, averaged across all replicates. Across all crop types at this site, no significant difference was observed between the treatment of silicon and control. Visual differences were observed with silicon-treated plots showing slightly higher growth and extended green foliage compared to their non-treated counterparts.

Table 3 Biomass results

Table 4 Harvest traits

Table 5 Grain traits

The native corridor area will be analysed throughout the duration of the project to understand the effect native vegetation on the soil biodiversity and nearby cropping systems. These results will be included in future Trial Book articles.

Silicon is a micronutrient that has been used in previous drought-stress trials under controlled and field conditions at The University of Melbourne. Silicon induced tolerance to abiotic stresses, such as drought, promotes enzymatic activities, and therefore improves photosynthetic efficiency. Results from previously published research trials showed that silicon applications have improved water relations through higher water uptake by roots, reduced water loss from leaves, and improved antioxidant defense mechanisms.

Silicon application may have potential to improve grain quality by increasing antioxidant compounds in the grain. Silicon application can potentially increase the soil microbial biodiversity and nitrogen fixing capacity in legumes.

Conclusion

Previous research trials have confirmed that the effects of silicon on plants are primarily seen in times of stress (such as drought and heat). It can be inferred that no significant differences were seen between the treatment of silicon and control (no silicon) across all crop types, due to the extremely wet seasonal conditions, including flooding, across the sites. Extended stay-green phenotypes were observed in spring wheat, providing a reasonable indication of the positive effect of foliar silicon application regardless of waterlogged conditions.

Acknowledgements

This project is led by The University of Melbourne (Project lead – Associate Professor Dorin Gupta), with partners Riverine Plains, Birchip Cropping Group, Gap Flat Native Foods, Goulburn Broken Catchment Management Authority and Black Duck Foods. Riverine Plains would like to thank its farmer hosts, Ian and Kaye Wood, and Adam and Ingrid Inchbold for the use of their land and support throughout this trial.

Author: Rhiannan Mcphee, Riverine Plains