Design and experiments of the side-deep fertilization device with sliding-knife furrow opener and pneumatic ejector for a liquid fertilizer atomizer

This study aims to increase the fertilizer utilization rate for less fertilizer pollution in paddy fields. A side-deep fertilization device was developed to combine with the sliding-knife furrow opener and the pneumatic ejector for the liquid fertilizer atomizer using the side-deep fertilization and liquid fertilizer. The fertilizer was applied to the soil near the rice root zone. The structure of the inner cavity was designed for an air-liquid coaxial pneumatic ejector fertilizer atomizer. A full factorial soil bin test was conducted with the nozzle-throat distance, the mixer (throat) diameter, and air pressure. A systematic investigation was also made to explore the effects of each factor on the fertilizer discharge (liquid fertilizer mass flow rate) and air consumption (air flow). The findings indicate that the influencing factors of the liquid fertilizer mass flow rate were ranked in descending order of the mixer (throat) diameter, air pressure, and nozzle-throat distance. Similarly, the influencing factors of the air flow were ranked in descending order of the air pressure, nozzle-throat distance, and mixer (throat) diameter. The structural design was simulated and then optimized with the EDEM software. The Weighted Mark Method was used to comprehensively evaluate the simulation. The optimal performance was achieved in the sliding-knife furrow opener at various working rates when the sliding-cutting angle was 32.5˚ and the cutting-edge angle was 45˚. A soil bin test was implemented to verify the simulation. The measured and simulated traction resistance were 8.5, and 6.9 N, respectively, with a relative error of 18%, where the simulated soil disturbance area was 1965.6 cm², when the ditching depth of the sliding-knife furrow opener was 30 mm, and the forward speed was 1.2 m/s. Meanwhile, the measured and simulated traction resistance were 14.4 and 12.2 N, respectively, with a relative error of 15%, where the simulated soil disturbance area was 2137.2 cm² when the ditching depth was 50 mm and the forward velocity was 0.6m/s. When the ditching depth was 30mm and the forward speed was 1.2 m/s, the standard deviation of fertilizer discharge was 0.2427 g/s, the relative error to the maximum fertilizer discharge was 1.42%, and the relative error between the ditching depth and the fertilization depth was 4.4%, according to the soil bin performance test. When the ditching depth was 50 mm and the forward speed was 0.6 m/s, the standard deviation of fertilizer discharge was 0.479 6 g/s, the relative error to the maximum fertilizer discharge was 2.13%, and the relative error between the ditching depth and the fertilization depth was 2.1%. The finding can serve as promising guidance for the application of side-deep fertilization of liquid fertilizer in paddy fields.