In a large synthesis of rehabilitation monitoring data of mined lands in Australia’s arid north-west, covering > 150 permanent monitoring transects, 10 years of repeat sampling and six mining operations, it was identified that much of the target perennial grass community was not being re-instated via standard seeding practices to levels comparable to un-disturbed ecosystems (i.e. < 20% of rehabilitation transects contained sufficient perennial grass density and cover values when compared to reference conditions). This assessment raised considerable concerns for both the mining industry operating in the region and the regulators who govern mining licences and site relinquishment.
Since then, considerable effort has been placed on understanding the biological limitations of seeds when used in these rehabilitation programs. Significant fail points have been identified at the germination and emergence phases across a wide range of plant diversity. However, we have now shown that, if you manage commercially supplied seeds for their quality, dormancy state, and provide species-specific seed enhancement treatments, you can increase seedling emergence from less than 5% to over 40%. This represents a significant improvement in our ability to use seed efficiently in severely degraded landscapes.
It is with this knowledge-base that we have shifted our focus to investigate a range of seed enhancement technologies (e.g. extruded seed pelleting) and precision seeding technologies (e.g. modified disc and press wheel direct seeding arrangements) that can further bolster the potential of seedling establishment.
Results/Conclusions
In our most recent field trials, we have shown that when seeds are sown on the soil surface, germination and plant establishment is almost completely absent. Additionally, when sown at or below 30mm in rocky soils there is over a 35% chance that an emerging seedling will encounter a rock impacting its ability to emerge once germinated. This introduces an additional bottleneck that is rarely considered.
In this presentation, we will discuss several biological, technological, and precision-engineering solutions that that have been developed to overcome these newly identified seed-use shortfalls. Two examples will be showcased that highlight the use of: 1) modified extruded pellets that embed seeds in a beneficial soil matrix allowing surface sowing and the promotion of seedling emergence in the dominant grass genus, Triodia, and; 2) custom designed seeding machinery that incorporates seeds into the upper soil surface on sloped, rocky landforms. Both techniques show promise for scalability across mined land in Australia and across the globe.