Rehabilitating a watercourse improves water quality, reduces erosion, provides habitat for birds and improves on-farm production. However, which are the best plant communities to do the job?
With the support of the Natural Resources Adelaide and Mount Lofty Ranges and 25th Anniversary Landcare Australia Grant Scheme funding, the Barossa Improved Grazing Group (BIGG) is helping landholders investigate how effective different native plant communities are at watercourse rehabilitation.
The project is exploring and demonstrating native plant communities that provide 100% annual groundcover to help stabilise soil, prevent erosion and reduce runoff, and those that improve habitat for birds by having perching, nesting and feeding sites.
It will compare the cost–benefit of different communities.
The project began in May 2015 on Klemm’s dairy farm in Moculta by fencing off a 250 m length of watercourse that runs during winter months and was significantly pugged through summer months. The centre of the watercourse had 10–20% ground cover and areas along the bank were completely bare. Before planting, woody weeds – more than 20 briar rose plants, and artichoke and thistles – were removed, and plant species and birds surveyed.
Tubestock was planted in July after a shroud spray to remove initial weed competition. Plant communities local to the area were planted in replicated 20 metre plots and compared against three control areas.
The communities were:
- native grasses including wallaby, kangaroo and spear grass
- understory plants (approx. 60 cm tall), including Juncus, Lomandra and Hardenbergia species
- trees including sheoak, peppermint box and red gums
- trees and midstorey plants including Acacia, Bursaria and Dodonaea species.
Due to the extremely dry spring, the plants were watered in October, December, January and early March.
Year 1 results
The most noticeable results one year later were the reduced pugging and groundcover over 90–100% of the entire site. These results would significantly reduce the risk of erosion and runoff, and improve water quality. They demonstrate the effectiveness of simply removing stock from the watercourse area.
Even in the dry conditions, more than 70% of plants survived, with most losses from the understorey plant plots. Most planted Juncus species did not survive, but plants originally there have thrived and flourished – a much cheaper option than tubestock planting!
Weed control has been a continual problem with Caltrop, which was already present in small numbers, flourishing in areas sprayed out for plants. It will continue to be monitored but should decline with competition from the native plants.
Plans for the future
In the second year of the project, an adjacent section of watercourse will be fenced off to determine the cost effectiveness of machine direct seeding. As the plants become more established, the bird and fauna surveys will be repeated. The benefits of increased pasture production through rotational grazing and improved milk production as a result of shade and shelter for the cows will also be determined.