The Derwent Catchment Project – Forage Shrub Trial
| Project start date: | 30 July 2019 |
| Project end date: | 15 June 2023 |
| Project status: | In progress |
| Livestock species: | Grass-fed Cattle, Sheep, Lamb |
| Relevant regions: | Tasmania |
| Site location: | Tasmania |
Summary
The Derwent Catchment has a semi-arid climate and suffers from episodic droughts which are likely to increase with a changing climate. The predominant land use in the region is dryland grazing which is reliant on pastures and runs. The pastures are under increasing pressure and are unreliable in times of drought. Cleared North-facing slopes have been recognised as a particularly fragile component of dryland enterprises in the Derwent Catchment, as they are difficult to incorporate into grazing system without significant environmental impacts.
Research has identified that forage shrubs are an
ideal management option to improve grazing productivity of North-facing slopes in the Derwent Catchment. This Producer Demonstration Site will apply learnings from the mainland states and design, implement and evaluate the productivity benefits of forage shrubs in Tasmanian grazing systems and determine the profitability of their establishment.
Objectives
By the 1st of March 2023 the project will:
1. Have demonstrated and assessed the potential of perennial forage shrubs – over a minimum of two grazing seasons - to contribute to useful fodder to address the Winter feed gap on marginal land (North-facing slopes) in Tasmania by:
a. Increasing or maintaining liveweight of lambs (pre and post grazing weight), and
b. Increasing stocking rate (DSE) without associated environmental impact on ground cover
c. Increasing inner row pasture ground cover (kg/DM/ha)
d. Increasing available forage (biomass measured in kg/DM/ha) nutritional value comparison to pasture will be included
2. Have conducted a costed proof of concept for the establishment of forage shrubs on North-facing slopes comparing planting seedlings to direct seeding methods across 3 demonstration sites.
3. Have facilitated a peer learning group of core producers who drive demonstration site design, establishment and monitoring. This peer learning approach will be used to produce a proof of concept to increase uptake by the 11 core producers to incorporate the use of perennial forage shrubs on marginal areas of their grazing systems. This will be measured by evaluation of pre and post knowledge, capacity, skills and confidence of producers.
4. Have conduct workshops and field days and produce a range of supporting resources to showcase the demonstration site results to encourage adoption of key practices by 44 observer producers. Survey of 44 producers will be undertaken to assess changes to the likelihood of adoption.
Progress
The Derwent Catchment Project, with funding from Meat & Livestock Australia, undertook a Producer Demonstration Site (PDS) project that investigated whether forage shrubs could be established at a commercial scale on north-facing slopes in Tasmania. The benefits were two-fold; to add grazing value to marginal areas whilst introducing deep-rooted perennials to stabilise erosion prone north-facing slopes. The trial commenced in winter of 2021 on three 5 ha north facing sites using planted tubestock of Mediterranean saltbush (Atriplex halimus) and also involved direct drilling of 1 ha at the 3 sites. A 5-hectare control was also established at each site.
Pressure from native animals impacted two of the sites to the point that they did not establish. The successful site on a farm near Hamilton was at least 500m away from any remnant native vegetation. The direct seeding failed at all three sites. The project was rescoped to observe, monitor and report on the response of the shrubs at the established site to grazing and to share the learnings with our producer network. Detailed measurements pre and post grazing were taken from the Nareen saltbush site.
The shrubs regrew in the extreme dry of summer, in a drought, delivering green material on a north-facing slope between December and April 2024, when nothing else grew. Data indicates that post grazing shrub height increased on average by 29% and width by 48%. Growth appears encouraged by the grazing, despite the critical lack of water for the inter-row pasture. The site offers insight into a potentially valuable and durable grazing asset that could, over time, overcome the cost of establishment at ~$2,000 per hectare. The projection of increasing dry spells and drought under climate change could compound its value.
