Evaluation of drone-based herbicide application on economic indices and yield of transplanted rice (Oryza sativa L.)

Introduction

Rice (Oryza sativa L.) is the most extensively cultivated and consumed cereal crop worldwide, serving as a staple food for billions of people. In India, rice holds significant economic importance, providing direct employment to nearly 70% of the rural population (Saha et al., 2017) [1] . Globally, China ranks first in rice consumption, with approximately 155 million metric tons consumed during 2022-2023, followed by India with about 108.5 million metric tons in the same period. In terms of production, China also led during the 2021-2022 crop year with over 148 million metric tons of milled rice, while India ranked second with more than 129 million metric tons. Overall, global milled rice production was estimated to exceed 502 million metric tons in 2022-2023. Rice cultivation is constrained by several biotic and abiotic stresses, among which weeds are one of the most critical yield-limiting biotic factors. Weeds compete aggressively with rice plants for vital resources such as nutrients, moisture, and sunlight, thereby reducing crop productivity. Kumar et al. (2010) [2] reported that, in the absence of weed control, rice grain yield declined by 70.4% in 2006 and 67.4% in 2007 compared to effectively managed plots. Among different weed categories, grassy weeds exert the highest competitive pressure, followed by sedges and broadleaf weeds. A drone, or Unmanned Aerial Vehicle (UAV), is an aircraft operated remotely using software-guided flight plans embedded within its system, supported by onboard sensors and the Global Positioning System (GPS). Owing to their high adaptability and precision, UAV platforms are emerging as an effective alternative for aerial pesticide application (Wang et al., 2018) [3] . Initially developed for military purposes, UAVs have undergone significant transformation with advancements in sensor technologies, GPS, and accessible computing, leading to their widespread adoption beyond defense applications (Ehsani & Maja, 2013; Hogan et al., 2017) [4,5] . Owing to their versatility, drones provide an efficient and precise solution for aerial chemical spraying (Wang et al., 2018) [3] . They also support farmers by saving time and facilitating a range of agricultural operations, including soil fertilization, spraying, irrigation, crop health monitoring, planting, and livestock tracking. Furthermore, drones can function effectively in challenging conditions such as wet or sloping terrains, reduce labour requirements, and enable site-specific applications.

Materials and methods

A field experiment was conducted during the Kharif season of 2022 at the Rice Research Centre, Agricultural Research Institute, Rajendranagar, Hyderabad. The experimental site had clay loam soil with a neutral pH of 7.6, electrical conductivity (EC) of 0.71 dS m -1 , and organic carbon content of 0.45%. The soil was medium in available nitrogen (212 kg ha -1 ), phosphorus (28.2 kg ha -1 ), and high in potassium (452.6 kg ha -1 ). The experiment was laid out in a randomized block design (RBD) comprising seven treatments with three replications. The rice variety RNR-15048 was transplanted at a seed rate of 50 kg ha -1 , maintaining a spacing of 15 cm × 15 cm with two seedlings per hill. Nutrient management involved the application of 120:60:40 kg ha -1 of N, P 2 O 5 , and K 2 O through urea, single super phosphate, and muriate of potash. The full dose of phosphorus was applied as a basal application, while nitrogen was applied in three equal splits at transplanting, maximum tillering, and panicle initiation stages. Potassium was applied in two equal splits at transplanting and panicle initiation. Herbicides were applied at different crop stages, with pre-emergence (PE) herbicide applied 3 days after transplanting (DAT) and postemergence (PoE) herbicide applied at 30 DAT. For ground application, 500 L ha -1 of spray fluid was used with a flat-fan nozzle-fitted knapsack sprayer, whereas drone application utilized 40 L ha -1 of spray volume. Observations were recorded on key growth and yield parameters, including plant height (cm), number of tillers (m -2

), number of panicles (m -2

) at harvest, grain yield (kg ha -1 ), and weed dry matter at 60 DAT.

Table 1. Details of the treatments

Treatment No.

Treatment details T 1 Application of penoxsulam 1.02 % + cyhalofopbutyl 5.1% OD @ 120 g a.i ha -1 using knapsack sprayer. T 2

Application of penoxsulam 1.02 % + cyhalofopbutyl 5.1% OD @ 90 g a.i ha -1 using drone. T 3 Application of penoxsulam 1.02 % + cyhalofopbutyl 5.1% OD @ 120 g a.i ha -1 using drone. T 4 Application of penoxsulam 1.02 % + cyhalofopbutyl 5.1% OD @ 150 g a.i ha -1 using drone. T 5 Application of penoxsulam 1.02 % + cyhalofopbutyl 5.1% OD @ 180 g a.i ha -1 using drone. T 6 Weed free (Hand weeding at 20, 40 and 60 DAT) T 7 Unweeded control

Results & discussion

Economics as influenced by different weed management practices

The effectiveness of any production system is ultimately evaluated on the basis of economics. The economic indicators such as gross returns (₹ ha -1 ), net returns (₹ ha -1 ) and B:C ratio were worked out and these indicators were analysed statistically and presented in the Table 2. Significantly highest gross returns were obtained with T 6 (weed free hand weeding at 20, 40 and 60 DAT) it was statistically on par with T 5 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 180 g a.i ha -1 using drone), T 1 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i ha -1 using knapsack sprayer), T 4 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 150 g a.i ha -1 using drone), T 3 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i ha -1 using drone) followed by T 2 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 90 g a.i ha -1 using drone). The lowest gross returns were obtained with T 7 (unweeded control). However, in terms of net returns higher net returns was obtained with T 6 (weed free hand weeding at 20, 40 and 60 DAT), it was statistically on par with T 5 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 180 g a.i ha -1 using drone), T 1 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i ha -1 using knapsack sprayer), T 4 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 150 g a.i ha -1 using drone) and T 3 (application of penoxsulam 1.02% + cyhalofopbutyl 5.1% OD @ 120 g a.i ha -1 using drone) followed by T 2 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 90 g a.i ha -1 using drone). The lowest net returns were obtained with T 7 (unweeded control). Similarly, higher benefit cost ratio was recorded (2.38) in T 3 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i ha -1 using drone) followed by T 1 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i ha -1 using knapsack sprayer) (2.37) and lower B:C ratio was noticed with un weeded control (1.11) because severe competition for nutrients throughout the crop growing season. Different weed management practices maintained less crop weed competition and higher nutrient availability which resulted in higher yields and high returns. Similar results were reported by Ramachandra et al. (2014) [6] , Yadav et al. (2018b) [7] and Yogananda et al. (2019) [8] . The herbicide application cost was comparatively more for knapsack (12 to 23%) than drone application. It was attributed to increased labour wages for herbicide application. Garre and Harish (2018) reported that the production cost can be reduced up to 20% through drone application of pesticides. The highest grain yield and gross return were recorded in weed free hand weeding. However, the high incurred cost for weed control resulted in lesser net return and benefit cost ratio (BCR) than all herbicide treated plots. Similar finding were reported by Paul et al. (2023) [9] .

The data pertaining to grain yield was significantly influenced with various weed management practices was analysed statistically and results were presented in Table 3. Rice grain yield was significantly higher in T 6 (weed-free condition maintained through hand weeding at 20, 40, and 60 DAT) and was statistically comparable with T 5 (application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 180 g a.i ha -1 using a drone), T 1 (application @ 120 g a.i ha -1 using a knapsack sprayer), T 4 (application @ 150 g a.i ha -1 using a drone), and T 3 (application @ 120 g a.i ha -1 using a drone). This was followed by a significantly lower grain yield in T 2 (application @ 90 g a.i ha -1 using a drone), while the lowest grain yield was recorded in T 7 (unweeded control). The results revealed that reducing the recommended dose of postemergence herbicide by 25% when applied through a drone (T 2 ) led to a 22.82% decline in rice grain yield, indicating that lowering the herbicide dose adversely affects yield performance. In contrast, increasing the recommended dose by 25% (T 4 ) and 50% (T 5 ) resulted in marginal yield improvements of 2.53% and 3.36%, respectively; however, these were statistically on par with the recommended dose (T 3 ). The findings clearly demonstrate that a reduction in herbicide quantity significantly reduced grain yield (4653 kg ha -1

) under T 2 treatment (Paul et al., 2023) [9] . Efficient utilization of light, water, and nutrients under conditions of low weed density and reduced weed dry matter resulted in the highest grain yield (6318 kg ha -1 ) with hand weeding at 20, 40, and 60 DAT. Effective weed management practices not only minimized weed density and biomass but also enhanced the crop's ability to utilize available resources efficiently. This improvement in resource use led to better growth parameters and yield attributes, ultimately resulting in higher grain yield compared to the unweeded control. Similar findings have been reported by Chowdhary and Dixit (2018) [10] , Kashid (2019) [11] , Singh et al. (2019) [12] , and Ramesha et al. (2019) [13] . The lowest rice grain yield was recorded under the unweeded control, primarily due to high weed density and biomass, which adversely affected all yield parameters. Similar findings were reported by Atheena et al. (2017) [14] and Venkatesh et al. (2019) [15] .

Treatments

T 1: Application of penoxsulam 1.02% + cyhalofopbutyl 5.1% OD @ 120 g a.i ha -1 using knapsack sprayer.

6207

T 2: Application of penoxsulam 1.02% + cyhalofopbutyl 5.1% OD @ 90 g a.i ha -1 using drone.

4653

T 3: Application of penoxsulam 1.02% + cyhalofopbutyl 5.1% OD @ 120 g a.i ha -1 using drone.

6029

T 4: Application of penoxsulam 1.02% + cyhalofopbutyl 5.1% OD @ 150 g a.i ha -1 using drone.

6186

T 5: Application of penoxsulam 1.02% + cyhalofopbutyl 5.1% OD @ 180 g a.i ha -1 using drone.

Conclusions

The economic analysis clearly demonstrated that effective weed management substantially improved the profitability of rice production. Weed-free hand weeding at 20, 40 and 60 DAT (T 6 ) recorded the highest gross and net returns owing to its superior weed control and higher grain yield. However, the higher labour requirement and associated cost of hand weeding reduced its economic efficiency. Among the herbicide-based treatments, drone application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i. ha -1 (T 3 ) recorded the highest benefit-cost ratio (2.38), followed by the corresponding knapsack application (T 1 ) with a B:C ratio of 2.37. The comparatively lower cost of herbicide application through drone technology contributed to its greater economic advantage over knapsack application. In contrast, the unweeded control (T 7 ) recorded the lowest gross returns, net returns and B:C ratio (1.11) due to severe crop-weed competition. Therefore, drone-based application of penoxsulam 1.02% + cyhalofop-butyl 5.1% OD @ 120 g a.i. ha -1 can be considered a cost-effective and economically efficient weed management option in rice, offering a favourable balance between crop productivity, weed control and production cost.

References

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