UAV-based herbicide application for efficient weed control and resource savings in direct-seeded rice

Abstract

Weeds pose a significant challenge to direct-seeded rice (DSR) as they hinder crop growth and yield. Farmers commonly use backpack sprayers (BS) for herbicide application to manage weeds. However, the manual application can be inconsistent, labor-intensive, and pose health risks to applicators. This research evaluates the effectiveness of unmanned aerial vehicles (UAVs) for herbicide application in management of weeds and assess labor, cost, and energy savings. A field trials were conducted at Tamil Nadu Agricultural University, Coimbatore, India during the kharif (August to November 2022) and rabi (December 2022 to March 2023) seasons. Treatments included UAV and BS application of pre-emergence (PRE), early post-emergence (EPOE), and post-emergence (POE) herbicides along with weed-free and weedy check plots. Results revealed that a single application of EPOE significantly reduced weed control efficiency (WCE) and recorded a yield reduction of 25–29% compared to sequential herbicide treatments. The combination of pretilachlor PRE followed by (fb) bispyribac sodium POE produced the highest grain yield in both application methods. Nevertheless, the UAV treatment yielded the highest net returns by reducing labor requirements (by 50%), application costs (by 18%), and total weed management costs (by 13%) compared to BS treatment. Furthermore, economic threshold analysis confirmed that the sequential application of herbicides through UAVs effectively balanced costs and yield gains. Additionally, UAV application significantly decreased the input energy, application time, and the energy required to produce 1 kg of rice compared to BS method. Our findings suggested that UAV application of herbicides, particularly the combination of pretilachlor PRE fb bispyribac sodium POE, is an effective weed control measure in DSR, while providing profitable yield, income, and energy returns for farmers. To conserve resources and effective weed management, UAVs can be serve as a viable alternative to conventional spraying systems for herbicide application in DSR.