Aspects of the Process of Sorting European Black Pine Seeds

Research Highlights: Seed separation criteria and the optimal parameters of sorting devices were described. Background and Objectives: Seeds are often sorted into fractions which are sown separately to promote uniform seed germination and seedling emergence. Therefore, the aim of this study was to determine the correlations between the basic physical properties of European black pine (Pinus nigra J.F. Arnold subsp. nigra) seeds for the needs of planning seed sorting operations. Materials and Methods: Black pine seeds were divided into 5 batches representing individual parent trees, and the physical properties (terminal velocity, thickness, width, length, angle of external friction, mass) of each seed were determined. The measured geometric parameters and seed mass were used to calculate the respective indicators for each seed. The values of the analyzed parameters were used to plan the seed separation process. Results: The average values of the basic physical properties of seeds were determined in the following range: Terminal velocity—8.32 to 8.73 m s ？ 1, thickness—2.24 to 2.27 mm, width—3.34 to 3.44 mm, length—5.87 to 6.08 mm, angle of external friction—28 to 32°, mass—18.8 to 20.0 mg. Seed mass was most highly correlated with terminal velocity, and it was least correlated with the angle of external friction. Conclusions: The results of this study indicate that black pine seeds should be sorted with the use of pneumatic separators or, alternatively, mesh sieves with longitudinal openings. These sorting devices separate seeds into fractions characterized by similar seed mass, which delivers both economic and environmental benefits in nursery practice