Economic analysis of herbicide application using drones for weed control in barnyard millet: A profitability perspective

Abstract

Barnyard millet is a key nutri-cereal known for its high nutritional value, drought tolerance, short growth duration, and suitability to climate-smart farming. Although traditionally grown under rainfed conditions, it is increasingly cultivated with irrigation to maximize yield. However, under irrigated conditions, weed infestation becomes a major constraint, reducing yield and increasing labor costs due to reliance on manual weeding. As a result, chemical weed control is steadily replacing conventional methods. The success of chemical weed management largely depends on accurate herbicide dosage and proper application techniques. Drone-based spraying offers a highly precise method, but requires optimization of herbicide quantity and spray volume for each crop. A study was carried out during the 2023-24 rabi season at ADAC&RI, TNAU, Tiruchirapalli, Tamil Nadu, using a Randomized Block Design (RBD) with three replications to assess the economic performance of drone-applied pre-emergence herbicides. The experiment included two doses of Pretilachlor (375 g/ha and 500 g/ha) combined with different spray volumes (40, 50, and 60 L/ha for drone spraying and 500 L/ha for manual application). These were compared against an unweeded control and the conventional knapsack sprayer treatment using Pretilachlor at 375 ml/ha with 500 L/ha spray volume. Weed control efficiency, grain yield, and economic return were recorded. Findings showed that the best weed control (91.9% at 15 DAT), highest grain yield (2195 kg/ha), and a benefit-cost ratio of 2.0 were obtained with Pretilachlor at 500 g/ha applied using a drone with a spray volume of 40 L/ha. This treatment produced 1311 kg/ha more grain than the untreated control. Compared to manual spraying of Pretilachlor at the same dose (500 g/ha) with a 500 L/ha spray volume, drone application at 40 L/ha yielded an additional net benefit of ₹4,350 per hectare, along with more timely and safer herbicide application.