Drought resilient pasture systems

WHY THIS PROJECT IS NEEDED

Central and southern NSW were once dominated by deep-rooted, perennial-based grassy woodlands. Since European settlement, landscapes have transformed to highly annualised systems, which has had a major impact on farm production and ecosystem health, function, and resilience, especially during times of drought.

This project aimed to use the latest research on species and management to increase the use of perennial pasture species within farming landscapes and increase resilience in dry seasons.

Drought resilient pastures contain a high proportion of productive perennial grasses, especially when accompanied by well adapted legumes inoculated with effective rhizobia. The establishment or enhancement of these pastures provides permanent habitat for above and below-ground biodiversity and protects soil from erosion and structural loss, while also buffering against high temperatures and rapid desiccation.

Drought resilient pastures also maintain higher organic matter and soil fertility levels, which can better support ecosystem function, particularly during times of drought. They can also suppress weeds, cycle nutrients, provide higher and more stable source of nutrition to stock and wildlife.

Drought resilient pastures can also aid recovery following drought, thereby increasing the profitability and stability of farm systems. The deeper roots of perennial pastures also increase carbon sequestration and water utilisation, reducing salinity, acidity and nutrient loss, while their ability to extract water from deeper in the profile can extend the growing season, increasing resilience in dry seasons.

Recent research also highlights their potential to reduce livestock methane emissions. As such, well adapted, more drought resilient pastures have the potential to contribute to Australia’s goals for both net zero carbon emissions by 2050 and an Agricultural Industry achieving $100bn in farm gate output by 2030.

Project focus

The project specifically aimed to help farmers build knowledge, skills and confidence to improve their pasture base, either by using practices to enhance favourable species already present, or by establishing new pastures. This helped address feed base management and farmer concerns around its impact on drought resilience.

A number of demonstration sites were established across the mid to high rainfall zones of central and southern NSW to showcase modern pasture species combinations and management practices known to build greater resilience into landscapes.

In the Riverine Plains, demonstration sites were established at Barooga and Savernake to identify the best pasture practices for local conditions.

• The site at Barooga aimed to demonstrate the benefits of rotationally grazing lucerne for improving pasture persistence, pasture quality and animal production.
• The Savernake site aimed to demonstrate the impact of lucerne seeding rate and variety on pasture persistence and quality.

Measurements were collected from both sites to quantify soil nutrition, establishment rates, species frequency and composition, biomass production and pasture quality. Lamb growth rates were also measured at the Barooga site to demonstrate the impact of rotational vs set stock grazing practices on animal production (data not presented).

Outputs from the demonstration sites have been modelled using decision support tools to explore environmental, production and economic impacts of practice changes on farm.

Field days and workshops, case studies, videos, publications and on-farm consultations helped communicate key learnings and outcomes from the project.

Project outcomes

Results from this project's 2023 trials were published in Research for the Riverine Plains, 2024.

Key messages were:

• Lucerne is a valuable perennial legume pasture capable of producing high-quality feed for stock from spring to autumn 
• Rotationally grazing lucerne-based pastures, to allow a rest period, is important for lucerne persistence and productivity, as well as the productivity of stock grazing it 
• To support persistence, lucerne sowing rates and cultivars should be selected to achieve target plant densities and productivity, while also being suited to the region’s rainfall, temperature, and type of farming system 
• At Savernake, lucerne quality declined from September to January before stabilising between January and March 
• Well-managed lucerne pastures are valuable options for improving livestock farmers’ drought resilience

Background

This project aimed to use the latest research on pasture species and management, to promote the use of perennial pastures within farming landscapes and increase resilience in dry seasons.

A species demonstration and grazing demonstration were established at Savernake and Barooga, respectively, in May 2023. These two demonstration sites aimed to showcase best-practice pasture management to build greater resilience for farmers in central and southern New South Wales.

Method

Pasture quality, plant frequency, plant species composition and biomass measurements were collected between spring 2023 to autumn 2024 at both sites, to monitor changes in pasture performance and persistence over the first summer of growth.

SAVERNAKE SPECIES DEMONSTRATION SITE

Aim
To demonstrate the impact of lucerne seeding rate and variety on pasture persistence and quality.
Table 1 Savernake species demonstration site treatments.
 
Method
The paddock was sown in late May 2023, with the treatments listed in Table 1.

Pasture quality samples were collected in mid- late September 2023 as well as mid-January and mid-March 2024. Lucerne and sub clover plant frequency, plant composition and biomass were measured in mid–late September 2023 and mid- March 2024 to measure differences before and after the first summer.

Table 1 Savernake species demonstration site treatments.

Results and Discussion
The lucerne and sub clover stands established well across all treatments, with the first grazing event occurring in mid-late January 2024. The eight-month period between sowing and grazing was intended to enable the lucerne to establish an extensive root base to support plant persistence. At the time of the first grazing, the lucerne in the control (lucerne / sub clover mix) appeared shorter and lighter in colour compared to Treatment 1 (heavy lucerne rate / sub clover mix) and Treatment 2 (two lucerne cultivars/ subclover mix).

Average lucerne and sub clover pasture quality was similar in September 2023, as shown by the key feed quality measurements in Table 2. Lucerne quality declined from September to January, as indicated by the increase in neutral detergent fibre (NDF) and decline in crude protein (CP) and metabolisable energy (ME), and then remained relatively stable between January and March. Lucerne quality was consistently similar across all treatments (data not shown).

Lucerne plant density remained stable over the first summer, as shown in Table 3, illustrating good initial pasture persistence. Sub clover is an annual plant which experiences seed dormancy over summer, and as such, density and composition (data not shown) were zero in March 2024.

Table 2 Savernake species demonstration site showing average lucerne and sub clover quality across all treatments

Note: Pasture quality samples analysed on a dry matter basis by near-infrared spectroscopy (NIR).

Table 3 Savernake species demonstration site plant density.

In September 2023, lucerne composition was greatest in Treatment 1 (heavy lucerne rate/sub clover mix), and similar between the control (lucerne/sub clover mix and Treatment 2 (two lucerne cultivars/sub clover mix). This was as expected given the heavier lucerne sowing rate in Treatment 1 (data not shown).
 
Total biomass was similar across all treatments at both measurement times, with the greater biomass recorded in Treatment 2 being attributed to a historic soil disturbance from the digging of a pipe beneath part of the treatment (Figure 1). Across all treatments, total biomass was greater in March than September, despite two short grazing periods in late January and early February.

Figure 1 Savernake species demonstration site Total biomass (kg DM/ha).

While little difference was found between the treatments at four and 10 months after establishment, it’s recommended that farmers sow the most appropriate species and cultivar at the best sowing rate for the region’s rainfall and temperature, and the type of farming system. This is important for maximising pasture production and persistence.

BAROOGA GRAZING DEMONSTRATION SITE

Aim
To demonstrate the benefits of rotationally grazing lucerne for improving pasture persistence, pasture quality and animal production.

Method
The site consisted of two 10 hectare dryland paddocks, “A3 West” and “A3 East”, which were sown to 9 kg/ha lucerne (cv L70) and 6 kg/ha arrowleaf clover (cv Zulumax) in late May 2023. Two irrigated 20 ha paddocks, “A7 West” and “A7 East”, which were sown to lucerne in 2019, were also included as part of the demonstration.

Pasture quality samples were collected on 9 October 2023, 19 January and 14 March 2024. As the A3 West and A3 East paddocks were sown to the same species and treated similarly, quality samples were combined across both paddocks. Lucerne quality samples from both A7 West and A7 East were also combined for measurement.
Lucerne and arrowleaf plant density, composition and biomass were collected on 9 and 30 October 2023 (data not shown) and 14 March 2024.

Results
Pasture quality was relatively similar between the A3 lucerne and A3 arrowleaf clover (Table 4). The lucerne quality was also similar between the A3 and A7 paddocks. The volunteer grasses in the A3 paddocks were predominantly annual
ryegrass, and had higher NDF and lower CP and ME than the legumes, reflecting their poorer quality.

Table 4 Barooga grazing demonstration site pasture quality

Note: Pasture quality samples analysed on a dry matter basis by near-infrared spectroscopy (NIR).

Lucerne and arrowleaf clover plant density remained stable over the grazing period, indicating appropriate sowing rates and grazing management (Table 5). The only notable decline in lucerne density over the summer occurred in A3 West, where the grass weeds population had increased by March 2024. Arrowleaf clover plants were not present in the A7 paddocks (not sown), or in March in the A3 paddocks due seed dormancy. As such, arrowleaf clover density (Table 5) and composition were zero at this time (data not shown).

The lucerne in A7 West and A7 East maintained almost 100% composition across all dates (data not shown). This, combined with the fact that the lucerne in these paddocks was more established and irrigated, likely contributed to its greater biomass at each sampling date (Figure 2). The late-summer dormancy of arrowleaf clover may have contributed to the lower total biomass in A3 West and A3 East during March.

Rotational grazing of all paddocks between October to March attributed to the decline in biomass between measurements (Figure 2). Similar weight gains were achieved for both mobs of wether lambs over the grazing period (data not shown).

Figure 2 Barooga grazing demonstration site total biomass (kg DM/ha) for each paddock

Summary

Selecting the best sowing rate, species, and cultivar of pastures for your region and farming system, and rotationally grazing perennial pastures, is important for maximising pasture persistence and production. Lucerne provides a relatively high-quality feed option over summer, with quality being greatest in spring and declining through to autumn. Well managed perennial plants are valuable for extending the growing season and carrying livestock over summer, given their extensive root system and summer activity.

Acknowledgements

This article was produced as part of the Creating landscape-scale change through drought resilient pasture systems project. This project is supported by the Southern NSW Drought Resilience Adoption and Innovation Hub Through funding from the Australian Government’s Future Drought Fund. Thank you to the Gorman and Bruce families for hosting the two demonstration sites.

Download the full article: Comparing pasture quality, persistence and liveweight gains in clover and lucerne based pastures

Webinar

As part of this project, a webinar covering pasture persistence and performance was held with Sophie Hanna from Riverine Plains, John Bruce from Barooga, Richard Hayes from NSW DPI and Susan Robertson from Charles Sturt University.

A recording of the webinar is available to view below.

This project is supported by the Southern NSW Drought and Innovation Hub, through funding from the Australian Government's Future Drought Fund.

Full project title: Creating landscape-scale change through drought resilient pasture systems.