QLD Department of Main Roads – Hydromulch Trials

Hydromulching road cuttings is an effective way of reducing erosion and providing soil coverage to bind the soil surface and retain organic matter and moisture. Organic matter, fertiliser and soil ameliorants are combined with water, glue and seed and then mechanically sprayed onto the bare soil surface.

The results of previous hydromulch trials on the Gillies Highway in 2004 indicated the importance of addressing soil deficiencies and increasing native species in the seed mixes.

Biotropica Australia coordinated the application of hydromulch works on the Gillies, Cook and Kuranda highways in the 2005 wet season, comparing different fertilizer types and the soil ameliorants, lime and Minplus™. In addition, trials were established to examine plantings of fishbone fern (Nephrolesis cordifolia) into rock gabion structures on the Kuranda Range in early 2005.

Monitoring after the 2005 wet season, indicated a good ground cover response, however sites were still very young and susceptible to weed invasion. Monitoring at the beginning of the 2006 wet season, indicated native grass establishment was well underway.

By Autumn 2006, there were no discernible responses of sites to fertilizer and soil ameliorant treatment. Further monitoring after the 2005/2006 wet season, soil analysis and biomass production will aim to provide solid baseline data and reflect treatment differences.

Small hydromulch works on slippage sites on the Kuranda Range in the 2005 wet season, provide an example of research culminating in very successful hydromulch application. After 12 months, there is 100% soil cover with contributions from all species present in the hydromulch mix. This cover result provides evidence that initial rehabilitation of road cuttings can be highly successful.

Biotropica Australia’s research into hydromulching techniques provides valuable information for clients wishing to rehabilitate large disturbed areas.