Primary study on physical properties of some vegetable seeds

China is the largest producer and consumer of vegetables in the world. Manual indenting and sowing of small vegetable seeds in plug trays is a slow and labor-intensive operation. Therefore, seeding operation of plug trays should be mechanized to increase the capacity of the rapidly expanding nursery industry. A tray precision seeding machine is one of the key devices used in industrialized plug seedling production. To reduce the miss-seeding and reseeding rates of seeders, we tested main varieties of different vegetables, such as cucumber, eggplant, pepper, and tomato, by obtaining their seeds (grain diameter ≤7mm) as materials. The physical characteristics (geometrical size, 1000-kernel mass, rest angle, and sliding friction angle) and aerodynamic characteristic (floating speed) of these vegetables were measured. The results showed that the average geometrical sizes (length, width, and thickness) were 9.00, 3.87, and 1.42 mm (cucumber); 3.07, 2.63, and 0.92 mm (eggplant); 3.96, 3.40, and 0.76 mm (pepper); and 3.23, 2.36, and 0.63 mm (tomato). One-thousand kernel mass values were 26.49, 4.27, 5.94, and 2.80 g, respectively. Rest angles were 19.36°, 19.83°, 20.56°, and 26.24°, respectively. Sliding friction angles (stainless steel plate) were 21.80°, 24.95°, 25.66°, and 31.82°, respectively. Finally, floating speed rates were 6.38, 5.02, 4.24, and 3.78m/s, respectively.