Customise the seeds, not the seeder: Pelleting of small-seeded species for ecological restoration

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Direct native seed planting is a cost-effective and popular approach for restoring degraded terrestrial ecosystems. However, the handling and precision seeding of multispecies mixes with diverse seed sizes, and shapes is logistically complex, requires highly customised equipment and often results in poor seedling establishment. This issue is accentuated in small-seeded species, where handling difficulties and a lack of precision placement result in seed wastage. The agricultural seed sector relies on the application of external material to small seeds to improve handling via seed pelleting. Yet this method has been rarely tested on small-seeded native species for ecological restoration.We pelleted the seeds of 15 small-seeded Myrtaceae species commonly used for seed-based restoration programs and recorded a range of physical traits. Prior to pelleting, each seed batch was tested for purity and viability and processed to improve quality (Pure Live Seed, PLS%). Seedling emergence from pelleted and control seeds was tested in controlled laboratory conditions and at two field sites in Western Australia. We linked seedling's emergence outcomes to the degree of physical modification achieved via pelleting to understand which trait would be responsible for a potential decrease or delay in emergence.Seed processing improved the average quality (PLS%) across all species from 23.4 ± 4.8% to 83.6 ± 2.3%. Seed pelleting, on average, resulted in a 27-fold increase in volume, a 30-fold increase in weight, and a 26% increase in bulk density. Seedling emergence response to pelleting varied among species, but on average, emergence speed was 3.1 days faster (p < 0.001) for pelleted seeds, while final emergence was not significantly different (p = 0.217).The results show that a combination of seed processing and pelleting can be used to increase and standardise seed physical properties for improved handling and precision seeding, with limited consequences on seedling emergence and faster emergence. This novel approach could enable the use of large-scale agricultural seeding equipment for rapid and cost-effective delivery of multispecies native seed mixes in biodiverse global restoration programs.