Study on Precision Seeding System Using Urethane Mat for Hydroponic Seedling Production of Leaf Vegetables (Part 2): Development of a Detecting Device of Missing Seed Using Digital Pressure Sensor

This study aims to develop a detecting device of missing seed for precision seeding system on hydroponic seedling production of leaf vegetables. In this seeding operation, seeds were planted by vacuum nozzles into pre-cut cells of urethane mat. It is important to detect whether the nozzles picked seeds or not for improving the seeding performance. Moreover the detection should be done automatically. The detecting device of missing seed using a digital pressure sensor was developed. Seeds of mustard spinach (Brassica rapa L. var. perviridis) and Chinese cabbage (Brassica rapa L. var. pekinensis) were used for the performance test of the detecting device. The detection level for setting the pressure sensor was determined and selected at 574 and 569 KPa to detect missing seed of mustard spinach and Chinese cabbage, respectively. The detecting device ould detect the missing seeds and compensate for the missing seeds without using any supplementary seeder. The average seeding efficiency was improved from 96. 5 to 99. 8% and from 97. 3 to 99. 6% for seeds of mustard spinach and Chinese cabbage, respectively. The number of missing cells per ten urethane mats was much reduced from 105 to 6 and from 81 to 12 for seeds of mustard spinach and Chinese cabbage, respectively.