Assessing the efficacy of extruded seed pellets and microbial amendments for native revegetation

Worldwide, there is a strong need for new, innovative, large-scale approaches to restoring diverse native vegetation. Seed-based revegetation, while often employed, can suffer from low plant establishment. Various seed coating technologies have been widely employed for decades to promote efficient agricultural planting; however, a significant obstacle to the implementation of this technology for native species revegetation is the limited access to the expertise and techniques which are mostly confidential to and specialized for the agrochemical industry. Here we investigated whether the seeds of Australian native species may benefit from extruded pelleting, measuring both seedling emergence and early growth, and testing the pellets with and without the addition of a commercial plant probiotic. A manipulative glasshouse experiment was carried out with three treatments (bare seeded; standard pellets; pellets amended with a probiotic) for four native plant species. Incorporation of seeds within standard pellets was shown to maintain high percentages of emergence and improve growth of three of the tested species (Daviesia ulicifolia, Hardenbergia violacea, and Indigofera australis) in the glasshouse setting, with increases in mean biomass of 83, 385, and 1,002%, respectively. However, emergence in the fourth species (Bursaria spinosa) was low in all seed treatments, perhaps due to excessive sowing depth (bare seeds), while combined with being encased inside a pellet. Relative to the standard pellets, probiotic amended pellets did not impart further detectable emergence or growth benefits. Ultimately, these results highlight exciting prospects for the application of extruded seed pellets in facilitating efficient use of seed in the revegetation of some native species.