Unmanned Aerial Vehicles (UAV) and Knapsack Sprayer Calibration and its Effects on Wheat Crop Growth

Precision agriculture seeks to raise yields while reducing inputs. In India, herbicide application is still dominated by knapsack sprayers, which are labour-intensive, slow, and prone to variability. This study evaluated whether unmanned aerial vehicles (UAVs) can deliver herbicides more efficiently and with comparable or improved crop response in wheat. A randomized block experiment with eight treatments was conducted at Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (Maharashtra). Vegetative growth metrics-plant height, functional leaves per plant, leaf area per plant (dm²), and tillers per plant-were recorded, alongside operational metrics: spraying time (h·ha⁻¹), water use (L·ha⁻¹), herbicide dose (kg a.i.·ha⁻¹), and labour (person-days). The control, weed free showed the strongest vegetative performance and among herbicide treated treatments the highest was observed in a treatment combination of pre-emergence herbicide via backpack sprayer followed by post-emergence application via UAV (Metribuzin 70% at 0.175 kg a.i.·ha⁻¹) integrated PE and POE weed management minimized weed interference and improved crop growth by ensuring better availability of nutrients and sunlight. Relative to manual techniques, UAV spraying reduced spraying time by up to 99%, water consumption by ~95%, and labour by ~85%, without compromising growth indicators. These results indicate that UAVs can augment herbicide delivery by enabling targeted, consistent, and resource-efficient applications in wheat.