domineering legumes is being considered, which might see the removal of D.“ Progardes” from proposed rehabilitation seed mixes for future sites( pers. Comm. J. Allen). Factors driving this increase in the legume D. progrades over grass species may include the depletion of the initial fertiliser, a lack of grazing of the legume and / or the sheer resilience of the legume. Inorganic and organic fertilisers were used at all large-scale sites( Sites 1-5). Organic fertilisers included bagasse, mill mud and hydromulch. The grass may have been relying on the fertiliser applied during the initial works and this may now be depleted. Without effective recycling of nutrients such nutrient sensitive plants will struggle. In contrast, the legume can fix nitrogen, a major plant nutrient( refer to Figure 11 and Figure 13). Secondly, to establish a balance of legumes and grasses, the legume may need to be grazed down while the plant is still establishing( Pers. comm. C. Poole). Early grazing of a site would have to be very carefully planned and managed.
Results indicate that Site 2 has achieved a balance of grass and D.“ Progardes”; Rhodes grass( Chloris gayana) was the primary species. Site 2 has maintained a high score with no drivers of reduced land condition. Future monitoring will be required to see if Sites 3 and 4 develop a better balance of legumes and grasses. At sites 1, 3 and 4 the Desmanthus tended to be tall(~ 1.5m). This is not the type of vegetation recommended for stabilising the sites- rather grass species are needed to provide cover close to the soil surface( Landloch Pty Ltd, 2024, P. 4). There are several more prostrate legumes that drop their leaves during the dry season that may be more suitable( pers. comm. C. Poole).
Sites lacked diversity in the plant species present. This is understandable given the harsh soil conditions for plant growth. Nevertheless, efforts should continue to improve seed mixes and revegetation techniques on the large-scale remediated gullies.
The treated catchments at Site 5 achieved high land condition rating( A condition) and were deemed fully stable. The bunds, rock chute and revegetation have maintained their integrity and have‘ settled’ into the landscape( refer to Figures 14 and 15). Works on the gullies and‘ bad lands’ only occurred in the upper parts of the southern section. The reduced stability of the gullies by December 2024, is attributed to the lack of remediation work in the gullies themselves. In the southern section, limited works were planned after costing revealed that the amount of ameliorants needed to make the older, lower areas suitable for revegetation would be uneconomical. The extensive landforming works that were planned for the northern gully section were not undertaken after discovering a large amount of rubbish at the site. Consequently, Site 5 ended up being like a small-scale treatment.
What changes to planning and design are recommended to improve large-scale gully remediation?
Focus on revegetation
The revegetation was impacted in the initial stages by sheet and rill erosion due to rainfall events. The subsequent repair work impacted the sites further. Site recovery is likely to be faster when the revegetation is dominated by grasses and is successfully established in the first year.
Refinements to the revegetation approach could include:
• Grass seed mixes with careful consideration of the inclusion of legumes. More information on legumes and sown pastures is available through the North Queensland Pasture Resilience Program. This program can be found on the Future Beef website where there are fact sheets, resources and contact details for personalised support.
• Functional trait-based species selection( e. g. Halophytes at Site 5).
• Improved seedbed preparation and soil-seed contact: Tilling, seed tackifiers, hydromulch, mycorrhizal fungi inoculants, soil microbiome enhancements.
• Irrigation to get initial grass establishment but with plans( e. g. fencing) for managing wild grazing animals( e. g. wallabies) that could, subsequently, be attracted to the site.
• Mulch and / or crushed rock to cover all reshaped gully areas( Wilkinson et al., 2022, p. 51). When rolled or spread out on the contour the mulch can provide effective
42 GULLY MAINTENANCE AND MONITORING TECHNICAL REPORT