Breaking physical seed dormancy in Parkinsonia praecox (Ruiz & Pav. ex Hook.) Hawkins: a comparison between chemical and automated mechanical scarification for arid land restoration

Arid lands worldwide are facing serious desertification driven by anthropogenic impacts. In this context, seed-based restoration is a cost-effective solution. However, its implementation poses challenges, such as breaking seed dormancy with procedures suitable for large quantities of seeds. We evaluated two large-scale scarification techniques in Parkinsonia praecox, a species with physical seed dormancy. Chemical scarification with H2SO4 was applied for 45 min (T1), and mechanical scarification was performed using a specially designed low-cost machine at 2.45 MPa and 10 Hz for 120 (T2), 180 (T3), and 240 s (T4). Seedling emergence, mean emergence time (MET), seed coat abrasion, and cotyledon green index (GI) were measured. The three scarification treatments (T1, T3, and T4) together significantly increased emergence by ∼300% (range: 293–373%) and decreased MET by ∼40% (range: 35–38%) compared to the control (T0). Seed coat abrasion increased significantly from T0 to T1 to T3. Cotyledon GI was lower in treated seedlings than in the control, suggesting a possible reduction in cotyledon functionality, with similar effects among chemical and mechanical treatments. Our findings confirm that mechanical scarification breaks seed dormancy just as effectively as chemical treatments. Construction of mechanical scarifiers from low-cost, locally available materials offers a safe, predictable alternative for arid land restoration, eliminating the health hazards and environmental risks associated with chemical methods.