An air-assisted mechanical hill-seeding device for foxtail millet (Setaria italica)

Setaria italica (foxtail millet) plays an important role in human nutrition, animal feed, and agriculture. Precision seeding is difficult, making foxtail millet planting and industrialization difficult. We designed an air-assisted mechanical foxtail millet hole seeder with a duckbill hole-forming device to address suboptimal seeding effects. We examined the effects of the return spring wire diameter, seed-metering device vacuum pressure, and dibber wheel rotational speed on seeding performance using bench testing. The results show: i) Wire diameters of 1.4, 1.6, and 1.8 mm were tested for quality index compliance with a return spring with a 44-mm major diameter, 2-mm minor diameter, and 70-mm length. A 1.4 mm wire diameter was chosen due to reduced tearing; ii) the seed-metering device vacuum pressure and dibber wheel rotational speed affected the quality index. We optimized parameters using response surface methodology to maximize the qualification rate and minimize missing and double seeding. An inlet vacuum pressure of -7.8 kPa, dibber wheel speed of 75 r/min, and seeder forward speed of 1.69 m/s (6.08 km/h) were optimal. According to model predictions, these settings had 89.88% quality, 1.56% multiples, and 8.56% miss. Field tests showed that at a seeder forward speed of 1.67 m/s (6 km/h) and a metering device vacuum pressure of -7.8 kPa, the average seed spacing was 16.51 mm, the hole spacing coefficient of variation was 2.55%, the mean seeding quality index was 88.46%, and the seedling pass rate was 97.77%. Thus, the air-suction-assisted mechanical foxtail millet hole seeder meets standards and advances small-grain crop agricultural machinery.