Optimization and evaluation of weed control performance in variable-rate patch spraying in field: Small-scale prescription operation

Weed management is an important means to ensure crop production, and the extensive use of herbicides destroys the ecological balance of farmland and enhances weed resistance. In this paper, an intelligent boom sprayer for cooperative air-ground operations is developed based on the spatial distribution characteristics of weeds in maize fields in the Huang-Huai-Hai region of China. According to the spraying accuracy requirements and application strategies, a large field small-scale gridded patch spraying method for weed control is proposed, and a small-scale field variable-rate operation prescription map is created. The optimal application conditions for reducing droplet drift during patch spraying were analyzed using water-sensitive paper. The machine was operated at 3.6 km/h traveling speed and 0.4 MPa spray pressure, and the variable-rate patch spraying was optimal at a spray height of 40 cm and a nozzle model of Teejet AIXR110–03 compact air-induction flat fan nozzle (spray angle: 110°, flow rate: 0.3 GPM). In the experimental dataset, the YOLOv8 is adopted object detection algorithm for the identification of maize seedlings and weeds. The dataset was processed through image cropping and data augmentation, resulting in a detection accuracy of 98% for maize seedlings and up to 94% for weeds. Three farmlands were selected for comparative tests based on spraying methods, assessing that all three test protocols met the practical production requirements, but spraying with small-scale gridded variable-rate patches performed better in terms of herbicide saving rate and weed mortality rate. In terms of herbicide saving rate, it saved 48.7% of herbicide dosage than wide-area spraying. In terms of weed mortality rate, it was 5.1% more than the large-scale variable-rate spraying, and had better weed control effect. Therefore, compared to existing spraying methods, utilizing this spraying strategy in field operation mode optimizes herbicide application, demonstrating superior environmental performance and economic benefits. • This paper proposes a small-scale gridded patch spraying method for weed control in large fields. • Generating prescription maps based on weed centroid coordinates for field operations. • Small-scale gridded variable patch spraying performed well in field. • The method reduces herbicide usage without compromising biological efficacy.