Evaluation of herbicide efficacy through weed indices in transplanted finger millet (Eleusine coracana L.)

Introduction

Finger millet (Eleusine coracana L.), commonly known as ragi, is an important climate-resilient small millet widely cultivated in semi-arid and rainfed regions of Asia and Africa. It plays a vital role in ensuring food and nutritional security, particularly among resource-poor communities, owing to its rich nutritional composition, including calcium, iron, dietary fiber, and essential amino acids (Devi et al., 2014) [3] . In India, it ranks third among millets after sorghum and pearl millet, with an average productivity of about 1524 kg ha⁻¹ (Anonymous, 2025) [2] . In Chhattisgarh, millets are cultivated over about 1.41 lakh hectares, accounting for nearly 6% of the total cultivated area of the state. The major millets grown include sorghum, pearl millet, finger millet and foxtail millet. Among these, finger millet occupies an area of 43,640 ha with a production of 39,407 tonnes and an average productivity of 903 kg ha⁻¹ (Anonymous, 2023) [1] . However, finger millet occupies a relatively small share of the cultivated area in the state compared to major millet-growing regions of India. Its productivity is also lower than the national average, primarily due to cultivation under rainfed conditions, marginal soils and suboptimal crop management practices. Nevertheless, finger millet holds significant potential for area expansion and productivity enhancement under suitable agro-climatic conditions, particularly with the adoption of improved production technologies and ongoing government initiatives promoting millet cultivation. Despite its adaptability, the productivity of finger millet remains low, primarily due to severe weed infestation. Weeds compete aggressively with finger millet for nutrients, moisture, light, and space, particularly during the early growth stages when the crop is a poor competitor. The critical period of crop-weed competition (25-40 days after sowing or transplanting) is crucial, and uncontrolled weed growth during this stage can cause yield losses of up to 61%, depending on crop cultivar, weed intensity, duration of infestation, and management practices (Mishra et al., 2018; Dubey and Mishra, 2023) [9,4] . Additionally, weeds increase the cost of cultivation, reduce produce quality, and serve as hosts for various pests and pathogens. Although manual weeding is effective, it is labour-intensive and often impractical during the kharif season. Therefore, herbicide-based weed management has emerged as an efficient and economical alternative for controlling diverse weed flora. However, information on the comparative efficacy and sequential application of herbicides in transplanted finger millet under Vertisol conditions of Chhattisgarh remains limited.

Materials and Methods

A field experiment was conducted during the kharif season of 2023 at the Instructional Farm, Dau Kalyan Singh College of Agriculture and Research Station, Bhatapara, Chhattisgarh, India (21.72° N latitude and 81.98° E longitude) at an altitude of 293.82 m above mean sea level. The experimental soil was clayey (Vertisols) with neutral reaction (pH 7.6), low in available nitrogen (117.6 kg ha⁻¹), medium in available phosphorus (20.5 kg ha⁻¹), and high in available potassium (382.0 kg ha⁻¹). The experiment was laid out in a randomized block design with eight treatments and three replications. The treatments comprised Weedy check (T₁), Pretilachlor 500 g ha ⁻1 3 DAT (T 2 ), Bensulfuron methyl + Pretilachlor (pre mix) 60+600 g ha ⁻1 3 DAT (T 3 ), Pyrazosulfuron ethyl 15 g ha ⁻1 3 DAT (T 4 ), Pretilachlor 500 g ha ⁻1 3DAT fb Penoxsulam methyl 20g ha ⁻1 25 DAT (T 5 ), Bensulfuron ethyl + Pretilachlor (pre mix) 60+ 600 g ha ⁻1 3DAT fb Penoxsulam methyl 20 g ha ⁻1 25 DAT (T 6 ), Pyrazosulfuron ethyl 15 g ha ⁻1 3DAT (PE) fb Penoxsulam methyl 20 g ha ⁻1 25 DAT (T 7 ) and Weed free (T 8 ). Finger millet variety 'Indira Ragi 1' was transplanted using 25day-old seedlings at a spacing of 30 cm × 10 cm, maintaining 2-3 seedlings per hill. The crop was fertilized with the recommended dose of 60 kg N, 40 kg P₂O₅ and 40 kg K₂O ha⁻¹. The full doses of phosphorus and potassium along with half of nitrogen were applied as basal, while the remaining nitrogen was top-dressed in two equal splits at appropriate growth stages. Preemergence herbicides were applied at 3 days after transplanting (DAT), while Penoxsulam methyl was applied as postemergence at 25 DAT using a knapsack sprayer fitted with a flat-fan nozzle. Standard agronomic practices were followed throughout the crop growth period. Weed-free plots were maintained by hand weeding, while irrigation was provided at critical stages as needed. Weed observations were recorded at 30, 60 and 90 DAT using a 1 m² quadrat placed randomly in each plot. Weed density and dry weight were recorded separately for grasses, sedges and broad-leaved weeds. Weed control efficiency (WCE) was computed to assess the effectiveness of treatments in reducing weed biomass relative to the untreated (weedy) control, following the method suggested by Mani et al. (1973) [8]: where, DWC is the dry weight of weeds in the control plot and DWT is the dry weight of weeds in the treated plot. Weed index (WI) was calculated to determine the reduction in crop yield due to weed competition in comparison with the weed-free treatment, as suggested by Gill and Kumar (1969) [5] :

where, x represents the yield from the weed-free plot and y represents the yield from the treated plot. The data were subjected to statistical analysis using analysis of variance (ANOVA) for a randomized block design, and treatment means were compared at the 5% level of significance following the procedure described by Panse and Sukhatme (1967) [10] .

Results and Discussion

Weed flora

The experimental field was infested with a diverse spectrum of weed flora comprising grasses, sedges and broad-leaved weeds (Table 1). Among the narrow-leaved weeds, Dactyloctenium aegyptium, Chloris barbata, Cynodon dactylon, Digitaria sanguinalis and Echinochloa colona were the predominant species, all belonging to the family Poaceae. Sedges were represented by Cyperus iria and Cyperus rotundus, indicating their adaptability under moist soil conditions. The broad-leaved weeds observed in the experimental field included Ammannia baccifera, Eclipta alba, Ipomoea pestigridis, Phyllanthus niruri, Rhynchosia minima, Trianthema portulacastrum and Tridax procumbens, belonging to diverse families such as Lythraceae, Compositae, Convolvulaceae, Euphorbiaceae, Fabaceae and Aizoaceae. The predominance of grassy weeds during the early stages of crop growth might be attributed to their rapid germination, vigorous growth and efficient utilization of available resources, enabling them to outcompete the crop during the initial growth period. In contrast, sedges and broad-leaved weeds appeared more prominently at later stages, thereby extending the period of crop-weed competition. The presence of such heterogeneous weed flora under Vertisol conditions highlights the complexity of weed management in transplanted finger millet and emphasizes the need for broad-spectrum and sequential herbicide application for effective control. These findings are in close conformity with earlier reports of mixed weed flora dominated by grasses, sedges and broadleaved weeds in finger millet, as reported by Kumara et al. (2007) [7] , Pradhan and Singh (2009) [12] and Pradhan et al. (2010) [11] , thereby reinforcing the necessity of effective weed management approaches in such cropping systems.

Weed control efficiency

Weed control efficiency was significantly influenced by different weed management practices at all stages of crop growth (30, 60 and 90 DAT) (Table 2). At 30 DAT, the sequential application of Pyrazosulfuron ethyl @ 15 g ha⁻¹ at 3 DAT followed by Penoxsulam methyl @ 20 g ha⁻¹ at 25 DAT (T₇) recorded significantly higher WCE (62.6%) over all other treatments. The next best treatments were Pretilachlor @ 500 g ha⁻¹ at 3 DAT fb Penoxsulam methyl (T₅) (43.6%) and Bensulfuron methyl + Pretilachlor (pre-mix) fb Penoxsulam methyl (T₆) (40.6%). At 60 DAT, application of Pyrazosulfuron ethyl @ 15 g ha⁻¹ at 3 DAT followed by Penoxsulam methyl @ 20 g ha⁻¹ at 25 DAT (T₇) again recorded significantly higher WCE (61.2%) compared to other treatments; however, it was found to be statistically at par with Pretilachlor fb Penoxsulam methyl (T₅) 56.6%), Pyrazosulfuron ethyl 15 g ha ⁻1 3 DAT (T 4 ) (49.6) and Bensulfuron methyl + Pretilachlor fb Penoxsulam methyl (T₆) (48.9%). Treatments pretilachlor @ 500 g ha⁻¹ at 3 DAT (T₂) and Bensulfuron methyl + Pretilachlor (pre-mix) @ 60 + 600 g ha⁻¹ at 3 DAT (T₃) recorded comparatively lower WCE and were at par with each other. At 90 DAT, significantly higher WCE (79.9%) was recorded under Pyrazosulfuron ethyl fb Penoxsulam methyl (T₇), which was at par with Pretilachlor fb Penoxsulam methyl (T₅) (74.7%) and Bensulfuron methyl + Pretilachlor fb Penoxsulam methyl (T₆) (70.0%), but significantly superior to other treatments. The effective control of early-emerged weeds under sequential herbicide application may be attributed to the pre-emergence application of Pyrazosulfuron ethyl, which is absorbed through both foliage and roots and subsequently translocated to the meristematic regions. It inhibits the acetolactate synthase (ALS/AHAS) enzyme responsible for the biosynthesis of essential branched-chain amino acids (leucine, valine and isoleucine), thereby arresting cell division and suppressing weed growth, ultimately leading to weed mortality. Further, the postemergence application of Penoxsulam methyl provided effective control of later-emerging weeds, resulting in a broad-spectrum weed suppression. Penoxsulam methyl is primarily absorbed through leaves and partly through roots, followed by translocation within the plant, exhibiting both knockdown and residual activity. It also inhibits ALS/AHAS enzyme activity, thereby disrupting amino acid synthesis and reducing weed dry matter accumulation. The weedy check (T₁) recorded zero weed control efficiency throughout the crop growth period due to the absence of weed management practices, resulting in unchecked weed growth and severe crop-weed competition. This led to higher weed biomass accumulation and depletion of essential resources such as nutrients, moisture, light and space, thereby adversely affecting crop performance. These results are in conformity with the findings of Kumar et al. (2023) [6] . Further, Sneha et al. (2023) [14] also reported higher weed control efficiency under sequential herbicide application involving Pyrazosulfuron-ethyl, whereas uncontrolled weed growth resulted in substantial yield reduction.

Weed index

Weed index varied significantly among different weed management practices due to differences in their effectiveness in reducing crop yield loss caused by weeds (Table 2). The significantly lowest weed index was recorded under weed-free treatment (T₈) (0.0%), which was found to be at par with Pyrazosulfuron ethyl fb Penoxsulam methyl (T₇) (4.1%). Among the herbicidal treatments, T₇ recorded the lowest weed index, which was statistically at par with Bensulfuron ethyl + Pretilachlor fb Penoxsulam methyl (T₆) (14.4%), indicating superior effectiveness in minimizing yield loss due to weeds. Higher weed index values were recorded under sole herbicide applications, viz., Pyrazosulfuron ethyl (T₄) (32.0%), Bensulfuron methyl + Pretilachlor (T₃) (33.1%) and Pretilachlor (T₂) (27.6%), indicating comparatively poor weed control due to limited residual activity and inability to suppress later-emerging weeds. The highest weed index (45.1%) was recorded under weedy check (T₁) due to severe crop-weed competition throughout the crop growth period. The lower weed index under sequential herbicide treatments may be attributed to effective and sustained weed suppression during the critical period of crop-weed competition, resulting in better utilization of nutrients, moisture, light and space by the crop, thereby enhancing yield. These findings are in close conformity with those of Kumar et al. (2023) [6] and Sneha et al. (2023) [14] , who also reported lower weed index and higher weed control efficiency under sequential herbicide application compared to single herbicide use. Similar results were also reported by Ramadevi et al. (2021) [13] and Pradhan and Singh (2009) [12] . The results clearly indicate that sequential herbicide application is more effective than sole herbicide use in managing diverse weed flora and minimizing yield losses in transplanted finger millet.

Conclusion

Sequential application of Pyrazosulfuron ethyl @ 15 g ha⁻¹ at 3 DAT followed by Penoxsulam methyl 20 g ha⁻¹ at 25 DAT proved most effective, recording the highest weed control efficiency and lowest weed index, comparable to the weed-free treatment. Sequential herbicide applications were superior to sole applications, while the weedy check resulted in severe cropweed competition and maximum yield loss. Thus, sequential herbicide application is an efficient strategy for weed management in transplanted finger millet.

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