A non-contact intra-row weeding device for rice based on high-speed gas jet: Design and experiment

Mechanical intra-row weeding is essential for promoting green production of rice and enhancing yield. However, conventional weeding devices are hindered by low weeding rate and high seedling damage rate. This study aimed to design and optimise a non-contact intra-row weeding device utilising high-speed gas jet to improve weed control and reduce seedling damage. A comprehensive investigation was conducted, integrating gas jet dynamics with the non-Newtonian properties of mud. Theoretical analyses determined the necessary conditions for sonic gas jets and derived a criterion for determining whether the airflow can disturb the mud. Factors influencing jet penetration length and optimal jet parameters were explored through theoretical analysis and practical experiments. A three-factor, five-level quadratic rotated orthogonal experiment was conducted, using nozzle-to-seedling distance, front-to-rear nozzle distance, and machine forward speed as experimental factors, and weeding rate and seedling damage rate as the response variables. Parameter optimisation achieved a weeding rate of 88.07 % and a seedling damage rate of 1.71 %, satisfying agronomic and technological requirements for paddy field weeding. The optimal parameters were a nozzle-to-seedling distance of 0.110 m, a front-to-rear nozzle distance of 0.080 m, and a machine forward speed of 0.25 m s⁻¹. The results demonstrated that the non-contact weeding device had a low seedling damage rate while maintaining a high weeding rate. This study presents an innovative solution to address the limitations of traditional mechanical weeding, which contributes to the innovation of mechanical inter-plant weed control technology in rice and thus promotes its green production.