Unmanned aerial vehicles (UAVs) represent a cutting-edge technology that holds the promise of revolutionizing the conventional tasks carried out in the realm of agriculture. On a global scale, UAVs are gaining prominence for pesticide applications, particularly with a focus on utilizing low spray volumes. Nevertheless, there remains a notable gap in research concerning the impacts of employing low spray volumes on herbicide efficacy. Hence, multi-location field studies were conducted at Agricultural Research Station, Bhavanisagar and Wetland Station, Coimbatore, Tamil Nadu, India in 2022 to evaluate the impact of different spray volumes using UAV and Knapsack Manual Sprayer (KMS) on droplet deposition, droplet density, and weed control efficacy. The treatments included UAV sprays at 30 and 45 L ha^-1, as well as KMS at 500 L ha^-1, with a weedy check as a control. Bispyribac-sodium 10% SC was applied at a rate of 35 g a.i ha^-1 during the 2-to 3-leaf stage of the crops. The results revealed that droplet deposition, area coverage, and volume median diameter were affected by sprayer type (UAV and KMS). However, the two spray volumes tested using the UAV method provided similar droplet parameters. The KMS system at 500 L ha^-1 exhibited the highest droplet deposition, while the UAV system achieved better droplet distribution at a spray volume of 30 L ha^-1. Remarkably, the UAV system at 30 L ha^-1 demonstrated effective weed control, which was statistically comparable to the KMS system at 500 L ha^-1. These findings emphasize that the UAV spraying system with a spray volume of 30 L ha^-1, delivering effective weed control while utilizing less carrier volume compared to the manual knapsack spraying method. Thus, the UAV spray system has great potential as a viable alternative to manual knapsack spraying for herbicide application in direct-seeded rice.

The bulbous vegetable onion Allium cepa Var. aggregatum L. (2n=16) is the most important species of Allium group and is regarded as the single most important vegetable spices as it forms an indispensable part of many diets, both vegetarian and non-vegetarian. Onion is valued for its bulbs having characteristic odour, flavor and pungency. Onion is regarded as a highly export oriented crop and earns a valuable foreign exchange for the country. Weeds are of great menace as they interfere with production of crop and add to the cost of cultivation. The reduction in crop yield has direct correlation with weed competition. Onion exhibits greater susceptibility to weed competition as compared to other crops due to its inherent characteristics such as their slow growth, small stature, shallow roots and lack of dense foliage. The effective weed control involves identification of weed flora, method of weed control and judicious combination of effective weed control methods. Hand weeding in onion is a common practice in India, but it is a tedious, expensive and time consuming task due to closer spacing and shallow root system. Non-availability of labourers during critical period of crop makes hand weeding difficult leading to heavy yield losses. Spraying of pre-emergence herbicides keeps the crop in weed free conditions during the early stages. At later stage, second flush of weeds will affect the bulb formation. Hand weeding helps to keep the weed population below economic threshold level throughout the crop growth period. Pre-emergence combined with hand weeding may be costly because of the reduced labour availability and higher labour cost. After bulb formation manual or mechanical methods of weed control will damage the bulb. Application of early post emergence may be helpful to reduce damage to the bulb, weed competition and cost of weeding. Hence a brief review was presented to find out the effect of different weed management method in onion.

Controlling weed populations in agricultural land is challenging due to various factors, such as soil conditions, crop type, and environmental conditions. Substantial experience is needed to develop a strategy for minimising pressure from weed...

Field experiments were conducted during Rabi 2018-19 (September to January) and Kharif 2019 (May to September). Medium duration rice cv. CO(R) 51 was used as a test variety at Tamil Nadu Agricultural University, Coimbatore, India to study the effect of Triafamone on broad spectrum weed control in transplanted rice. Triafamone was applied at two times. First set of treatments (30, 40,50 and 100 g/ha) applied two to three leaf stage of weeds and second set treatments imposed (30, 40,50 and 100 g/ha) at three days after transplanting of the rice crop. These treatments were compared with Pyrazosulfuron ethy 10% WP @ 15 g/ha, Pretilachlor 5% EC @ 750 g/ha, hand weeding @ 20 and 40 days after transplanting and unweeded control. The major grasses were Echinochloa crus-galli (L.) and E. colonum (L.) while the sedge weed included Cyperus nutans (L.). Among the broad leaved weeds Eclipta alba (L.) and Bergia ammanioides were the dominant species. In both the seasons of the study, lesser population of grass was recorded with the pre and early post emergence application of triafamone herbicide 40 g a.i. ha-1 (1.41 and 1.41 per m-2 at 28 and 42 DAA for both the seasons respectively) and it was closely followed by application of triafamone herbicide 50 g a.i. ha-1 and application of PE Pretilachlor at 0.75 kg a.i. ha-1 and EPOE Pyrazosulfuron ethyl at 15 g a.i. ha-1. The same trend was observed for broad leaved weeds and their weed dry weights. Application of triafamone herbicide at 40 g a.i. ha-1 as pre emergence and early post emergence application recorded highest weed control efficiency of 100, 97.7 and 99.6 % and 97.8% at 42 DAA during both years of experimentation and also resulted in higher grain yield (8052 and 8182 kg ha-1 during rabi 2018-19 and 9018, 9175 kg ha-1 during Kharif 2019). Further, it is noticed that, there was no residual toxicity of herbicide to the succeeding crops. Hence, application of Triafamone 40 g a.i. ha-1 either pre or early post emergence herbicide has higher productivity and no residues in transplanted rice ecosystem. Key words: Triafamone, efficacy, weeds and transplanted rice ecosystem