The effect of spray volume on weed control in transplanted rice ecosystems using the Unmanned aerial vehicle (UAV) needs to be better understood for management in the advancements of UAV-based spraying technology. The present study aimed to find out the influence of varied spray volumes of 15 L/ha, 20 L/ha and 25 L/ha using the UAV and 500 L/ha using a Knapsack sprayer (KS) to compare the weed density, weed dry matter and weed control efficiency and yield in transplanted rice (Oryza sativa L.). Pre-emergence (PE) application of Pyrazosulfuron-ethyl at 25 g a.i./ha at three days after transplanting (DAT) and post-emergence (PoE) application of Bis-pyribac sodium at 25 g a.i./ha at 25 DAT were used as herbicide treatments. The results revealed that varied spray volumes significantly influenced the weed density, dry matter, and weed control efficiency of the UAV and KS. Application of herbicides using KS (500 L/ha) and UAV (25 L/ha) had better control on the weeds by reducing weed density and dry matter at 20, 40, and 60 DAT, with no significant difference. Higher grain yield and straw yield were recorded in KS (500 L/ha) and UAV (25 L/ha), with no significant difference. However, applying 25 L/ha had better weed control efficiency and higher yield, possibly due to optimum deposition. Considering the low volume application of UAV (25 L/ha) as compared with KS (500 L/ha), it is better to go for the optimal application of 25 L/ha, which is an energy-efficient and cost-effective, labour-saving approach compared to KS.

A field experiment was conducted at the Agricultural Research Station, Tamil Nadu Agricultural University, Bhavanisagar, during 2021–23 to study the effect of spray volume (SV) on deposition characteristics of a fuel-operated UAV sprayer (25 L/ha, 37.5 L/ha and 50 litre/ha) and knapsack sprayer (KS) (500 litre/ha) in the rice (Oryza sativa L.) field. Results showed that herbicides spraying using UAV (37.5 litre/ha) had a higher droplet deposition (0.077 and 0.075 μL/cm2) than knapsack spraying of 500 litre/ha (0.06 and 0.049 μL/cm2) in the ground layer of first (PE) and second (PoE) spraying, respectively. KS (500 litre/ha) had significantly higher droplet coverage rate, droplet size (Dv0.5) over other UAV spray volumes. Subsequently, variation in spray uniformity was found between two sprayers. Among UAV spray volumes, application of 50 litre/ha had better deposition, coverage rate and number of spray deposits/cm2 compared to UAV (37.5 litre/ha), with no significant difference between them. Further, application of 25 litre/ha using UAV recorded lower deposition characteristics over other treatments. So, considering low volume application of UAV (37.5 litre/ha), comparable with high volume KS (500 litre/ha), it is better to go for optimal application of UAV (37.5 litre/ha), which is having better working efficiency, profitability and labor-saving approach compared to knapsack sprayer.

The experiment was conducted during summer and rainy (kharif) seasons of 2021 and 2022 at Agricultural Research Station (Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu), Bhavanisagar, Tamil Nadu to evaluate the efficiency, economics and energetics of drone-based herbicide spray (fluid) application in transplanted rice (Oryza sativa L.). During the experiment the application of pre-emergence and post-emergence herbicides was done using drone and knapsack sprayer to assess the weed control efficiency (WCE). Treatments included 3 herbicide combinations, viz. pyrazosulfuron ethyl as pre-emergence (PE); pyrazosulfuron ethyl as pre-emergence (PE) fb bispyribac sodium as PoE; and pyrazosulfuron ethyl as PE fb metsulfuron methyl + chlorimuron ethyl as PoE; and 4 spray fluids applied using drone and knapsack sprayer (25, 37.5, 75 and 500 litre/ha). Weed free and unweeded check plot were used as reference for calculating WCE. Application of pyrazosulfuron ethyl fb bispyribac sodium using knapsack sprayer reduced weed density from 77.74-86.45% and weed dry weight from 89.60-91.40% over unweeded plot. Moreover, it was found on par with drone application of 37.5 litre/ha using herbicides during both the seasons. Interaction effect between herbicides and drone spray fluids was found to be non-significant. Pyrazosulfuron ethyl fb bispyribac sodium application through knapsack sprayer (500 litre/ha) and drone (37.5 litre/ha) produced higher grain yield and straw yield. Higher net return, benefit: cost ratio (2.49 and 2.40), energy-use efficiency (13.44 and 13.40 MJ) and energy productivity (0.414 and 0.416 kg/MJ) were noticed with drone application of pyrazosulfuron ethyl fb bispyribac sodium using 37.5 litre/ha spray fluid in both the seasons. From the experiment, drone application of pyrazosulfuron ethyl fb bispyribac sodium with spray volume of 37.5 litre/ha was found as an effective strategy to manage weeds in transplanted rice and more advantageous in terms of energy-use efficiency and profitability.

Weed management is a critical challenge in modern agriculture, directly affecting crop productivity and quality. Traditional weed management techniques, such as manual weeding, mechanical tillage, and chemical herbicides, have significant drawbacks, including environmental impact, labor intensity, and the emergence of herbicide-resistant weeds. Recent advancements in drone technology offer new opportunities for precision weed management. Drones provide a cost-effective, efficient, and sustainable approach by enabling site-specific weed detection, monitoring, and control. This review provides a comprehensive overview of the use of drones in weed management, discussing their technological capabilities, applications, benefits, and challenges. It also explores the integration of drones with other precision agriculture technologies and highlights future research directions to enhance the adoption and effectiveness of drone-based weed management strategies.

Understanding the impact of urbanization on soil quality is crucial for sustainable land management practices. This study was conducted in Bengaluru, India, to estimate the soil quality index (SQI) under different rural‒urban gradient (RUG) zones. Twenty-four sampling sites were identified along the RUG, and soil samples were collected monthly over five months during the October to February of 2020-2021. The soil quality assessment involved selecting the minimum data set (MDS) via principal component analysis (PCA) and correlation, scoring soil indicators, and combining these scores to create the soil quality index (SQI). PCA was used to identify key soil properties, which included microbial biomass carbon (MBC), SOC, N, manganese (Mn), and urease for different RUG zones derived from the MDS. The rural zones had the highest SQI (0.57), followed by the peri-urban (0.47 and 0.48) and urban (0.45 and 0.47) zones. These findings emphasize the importance of sustainable land management practices to preserve and boost soil quality across diverse regions, particularly in the face of rapid urbanization and industrialization.

A field study was conducted on the efficacy of different herbicide spray fluids applied using drone and knapsack sprayer on weed density, dry weight and nutrient removal by weeds present in rice field of Wetland farm, Tamil Nadu Agricultural University, Coimbatore, during Kharif 2022. The experiment revealed that combined application of pre-emergence Pyrazosulfuron-ethyl (25 g a.i. ha-1) and post-emergence Bispyribac-sodium (25 g a.i. ha-1) using a hybrid drone with a flat jet nozzle and 37.5 L ha-1 spray fluid significantly reduced weed populations to 2.31 and 2.68 weeds m-2 at 40 and 60 days after transplanting (DAT), respectively. It also decreased weed dry weight to 2.60 and 2.99 g m-2 at the same intervals. This effective weed control is attributed to the suppression of subsequent weed germination in transplanted rice through the post-emergence herbicide application. Application of Pyrazosulfuron-ethyl (25 g a.i. ha-1) on 3 DAT as PE fb Bispyribac-sodium (25 g a.i. ha-1) on 25 DAT as PoE (H2) recorded significantly lower nitrogen, phosphorus and potassium at 40 and 60 DAT, respectively. Further, spray fluid of 37.5 L ha-1 was observed with lower nutrient removal by weeds, which might be due to lower weed density and dry weight.