Optimization of unmanned aerial vehicle operational parameters to maximize fertilizer application efficiency in rice cultivation

Unmanned Aerial Vehicles (UAVs) have experienced rapid development in rice topdressing applications in recent years, owing to their advantages of broad terrain adaptability, high operational efficiency, and minimal crop disturbance. However, current operational parameter configurations are lacking in systematic optimization, leading to suboptimal fertilization quality and compromised application efficiency. To address these challenges, this study investigated UAV-compatible fertilizer selection and operational parameter optimization. Fertilizer physical parameters were screened based on their compatibility with UAV spreading mechanisms, and an operational parameter optimization framework was developed using distribution uniformity as the key performance indicator, through which optimal operational parameters were determined. Furthermore, comparative field experiments were conducted to validate the enhancement of fertilizer application efficiency through UAV operational parameter optimization. Experimental results revealed that granular fertilizer parameters exert significant impacts on application quality. Critical thresholds were identified as moisture content below 0.5 %, sphericity exceeding 95 %, and density ranging from 1.2 to 1.4 g/cm³, which provide criteria for selecting and developing UAV-compatible fertilizers, addressing a key knowledge gap in precision UAV fertilization. The calibrated configuration of urea-ammonium nitrogen fertilizer application was determined, comprising a flight height of 3 m, a flight speed of 2 m/s, and a spreader disc rotation rate of 900 r/min, which established benchmark values for UAV fertilization. Field experiment demonstrated that UAV fertilization with optimization operational parameters achieved a 15.6 % increase in rice yield. This study establishes a systematic framework for UAV-based rice topdressing optimization, and an innovative solution to enhance fertilizer application efficiency is proposed.