AN ENNOVATING PRECISION SOWING UNIT FOR TRAY NURSERY

Aportable compact precision plug trayvegetable seeder wasmanufactured in Agricultural Engineering Research Institute (AEnRI) workshop to plant fine and large vegetable seeds with low cost and high seed singulation ratio. The seeder was depended on a controlled negative and positive pressure passed through a set of nozzles to pickup and drop the seeds into the tray cells. For tomato seeds, four nozzles holders equipped with 209 nozzles with inner diameters of (0.47 mm, 0.62 mm, 0.76 mm and 1 mm for each set) were tested with negative pressure of (1, 1.25, 1.5 and 1.75 kPa). For cantaloupe-melon, four nozzles holders equipped with 84 nozzles with inner diameters of (0.76 mm, 1.00 mm, 1.2 mm and 1.4 mm) were tested with negative pressure of (6, 7, 8 and 9 kPa). The performance of the seeder was evaluated using seed singulation efficiency, seeding efficiency, seeder productivity, specific energy requirement and seeding cost. The machine succeeded to plant large and small seeds in different types of plug trays. The optimum nozzle diameter for planting tomato seeds was 0.62 mm operated at negative pressure of 1.25 kPa that gave percentage of single seed 89.95%, double seeds 4.79%, multiply seeds 2.39% and missed seeds 2.87%. Meanwhile, the optimum nozzle diameter for planting the cantaloupe-melon seeds was 1.20 mm operated at negative pressure 8.0 kPa that gave percentage of single seed 94.05%, double seeds 2.38%, multiple seeds 2.38% and missed seeds 1.19%. The productivity of precision vacuum trays seeder was 320 tray/ h (66880 and 26880 cells/ h) for tomato and cantaloupe-melon seeds respectively. The total power requirement for the seeder was 1.075 kW.h for tomato seeds and 1.216 kW.h for cantaloupe melon seeds. The consumed specific energy was (3.36×10-3 kWh/ tray) for tomato seeds and (3.80×10-3 kWh/ tray) for cantaloupe melon seeds. The total operating cost was 43.37 LE/h. The cost of one tray seeded by the machine was 0.14 LE/ tray comparing with (0.67 and 1.67) LE/try for hand seeding of (cantaloupe melon tray and tomato tray) respectively. The total fabrication cost of the seeding machine was 15000 LE with 2016 price level. The rental value of mechanical seeding per tray was 0.20 LE. The seeding machine indicated net present value (NPV) of 2930 LE at 11 % interest rate. The seeding machine payback period was about 1.3 year.