An air-assisted mechanical hill-seeding device for foxtail millet (<em>Setaria italica</em>)

Abstract

Setaria italica (foxtail millet) plays an important role in human nutrition, animal feed, and agriculture. However, the difficulty in realizing precision seeding introduces challenges to the planting and industrialization of foxtail millet. To address the challenge of suboptimal seeding effects for foxtail millet seeds, we engineered an air-assisted mechanical foxtail millet hole seeder equipped with a duckbill hole-forming device. Through bench testing, we investigated the influence of the wire diameter of the return spring on the seeding effect, as well as the interactive effects of the vacuum pressure of the seed-metering device and the rotational speed of the dibber wheel on seeding performance. The results show the following. (1) With the return spring having a major diameter of 44 mm, minor diameter of 2 mm, and length of 70 mm, wire diameters of 1.4, 1.6, and 1.8 mm were evaluated for conformity with standard requirements for the quality index. Given the reduced tearing extent with a smaller wire diameter, a wire diameter of 1.4 mm was selected. (2) The vacuum pressure of the seed-metering device and the rotational speed of the dibber wheel had a significant impact on the quality index. Using the response surface methodology (RSM) for parameter optimization, we aimed to maximize the qualification rate and minimize the missing and double seeding rates. Optimal parameters were found with an inlet vacuum pressure of −7.8 kPa, a dibber wheel speed of 75 r/min, and a seeder forward speed of 1.69 m/s (6.08 km/h). These settings achieved a quality index of 89.88%, a multiples index of 1.56%, and a miss index of 8.56%, in accordance with model predictions. Field tests were conducted with the determined parameters, revealing 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 designed air-suction-assisted mechanical foxtail millet hole seeder complies with the standard requirements and represents an advancement in agricultural machinery for small grain crops.