Comparative study on droplet parameters and weed control efficiency under UAV and Knapsack manual sprayer for herbicide application in summer cotton

A field experiment was conducted during the summer season of 2024 at Pandit Jawaharlal Nehru College of Agriculture & Research Institute, Karaikal, Puducherry to evaluate the impact of different spray volume using Unmanned Aerial Vehicles (UAV) sprayer and Knapsack Manual Sprayer (KMS) on droplet deposition, density, distribution, drift and weed control efficiency. The experiment involved the application of pre-emergence herbicide namely pendimethalin 1 kg/ha under UAV spray at 25, 37.5, 50 L/ha compared with KMS 500 L/ha and unweeded control in a randomized block design with three replications. The findings indicated that the KMS system at 500 L/ha demonstrated the highest droplet count, whereas the UAV system provided better droplet distribution at a spray volume of 37.5 L/ha. The theoretical field capacity, effective field capacity and Field Efficiency (FE) are higher in UAV spray (7.2, 3.3 and 80.7) respectively, than KMS (0.3, 0.1 and 33.3) respectively. Spray drift got reduced whenever spray volume decreased and vice versa. Whereas, UAV spray volume of 50 L/ha recorded drift at a distance of 5 m, unlike the other spray volumes tested. The UAV system at 37.5 L/ha achieved better weed control effectiveness which was statistically comparable to the KMS system at 500 L/ha. These findings highlight the effectiveness of the UAV spraying system at 37.5 L/ha spray volume in achieving efficient weed control with better droplet distribution. Thus, the UAV spraying system holds considerable potential as a practical and efficient alternative to manual knapsack spraying for herbicide application in summer cotton.