Assessment of Weed Dynamics and Crop Response Through Integrated Weed Management Strategies in Drum Seeded Rice

Rice is one of the most important staple food crops for Asia and several countries in the world. Rice is grown globally on approximately 168.36 million hectares, producing about 799.99 million tonnes with an average yield of 4.7 tonnes per hectare (FAOSTAT, 2023). In India, rice is one of the most important crops occupying an area of 47.82 million hectares with the production of 137.82 million tonnes and having an average yield of 2.8 t/ha. In Tamil Nadu, total area of rice production was 21.01 lakh hectares, production was 67.99 lakh tonnes and productivity were 3235 kg/ha (Indiastat, 2024).
       
Increasing water scarcity, reduced labours and rice crop’s water loving character tend the farmers to look for an alternate method of cultivation. Direct seeded rice was able to reduce water usage and increase the water productivity (Kaur and Singh, 2017). At the present situation, transplanted rice has been replaced by the direct seeded rice which increases intensity of grasses than the broad-leaved weeds (Selvaraj and Hussainy, 2020). Due to continuous process of puddling in traditional transplanted rice, aggregates of the soil reduce which damages the stability creating hardpans which can be rectified by the direct seeded rice (Mir et al., 2023). Utilizing a drum seeder for direct wet seeding of rice offers numerous advantages, such as avoiding the nursery preparation and transplanting stages, facilitating faster and more straight forward planting and reducing water and labor requirements. This technique speeds up the crop maturity and improves water usage efficiency, resulting in a reduction of approximately 25% (250-300-man hours) in the total labor required for rice nursery preparation and transplanting, thus making rice production more financially sustainable (Raghavendra et al., 2015).
               
Despite the advantages, the main problem with direct seeded rice is weed infestation which is a major potential threat to rice crop. The absence of flooded water at the premature time of cultivation increases weeds in direct seeded rice (Shekhawat et al., 2022 and Ashraf et al., 2024). To control the weeds, single weed management strategy won’t be effective. So integrated weed management strategies should be used to eliminate the weeds. The effectiveness of DSR largely relies on improved weed management techniques. Several research findings indicate that relying on either pre-or post-emergence herbicides alone does not achieve adequate weed control during the growing season. In this regard, applying combination of pre- and post-emergence herbicides or combination with physical and mechanical methods was more efficient approach (Yogananda et al., 2021 and Vasantha Kokilam et al., 2023). Considering these factors, the impact of different herbicides and non-chemical methods was assessed against weedy controls to evaluate their effectiveness and achieve greater yields in drum-seeded rice.

The experiment was carried out during the Navarai season (Jan. - Apr.) of year 2025 at the wetland farm of SRM college of Agricultural sciences, Baburayanpettai, Chengalpattu district, Tamil Nadu, India. The coordinates of the experimental site are 12.38^o N latitude and 79.73^o E longitude at the elevation of 50 m above mean sea level. This site is classified as part of the North Eastern agro-climatic zone in Tamil Nadu, India. Prior to the experiment, the NPK levels measured were 217.4 kg/ha (low nitrogen), 12.8 kg/ha (medium phosphorus) and 140.3 kg/ha (medium potassium), respectively. The average pH was about 6.5-7.5 which is neutral and EC was 0.47 dsm^-1 which is low. The experimental design was laid out in randomized block design (RBD) and replicated thrice. The treatment details are T₁- PE Bensulfuron methyl + Pretilachlor @ 660 g/ha fb Hand weeding on 40 DAS, T₂- PE Bensulfuron methyl + Pretilachlor @ 660 g/ha fb Power weeding on 40 DAS, T₃- PE Bensulfuron methyl + Pretilachlor @ 660 g/ha fb PoE Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha, T₄- EPoE Trifamone + Ethoxysulfuron @ 67.5 g/ha on fb Hand weeding on 40 DAS, T₅- EPoE Trifamone + Ethoxysulfuron @ 67.5 g/ha fb Power weeding on 40 DAS, T₆- EPoE Trifamone + Ethoxysulfuron @ 67.5 g/ha fb Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha, T₇- PE Pretilachlor @ 500 g/ha on fb Hand weeding on 40 DAS, T₈- Power weeding @ 20 DAS and 40 DAS, T₉- Hand weeding @ 20 DAS and 40 DAS and T₁₀- Control.
       
The rice variety CO 55 was sown using the drum seeder (Fig 1 and 2). Pre emergence herbicide was applied at 3 DAS mixed with sand by maintaining a thin film of water. The early post-emergence and post-emergence were applied at 10 DAS and 25 DAS respectively, through a knapsack sprayer (Fig 3). The mechanical weeding was carried out as per the schedule using a two-row paddy power weeder (Fig 4). Hand weeding takes place as per the treatment schedule (Fig 5). All the package of practices were followed based on CPG (2020).










               
The observation on weeds viz. total weed density and weed control efficiency were recorded at 20, 40 and 60 DAS using a (0.5 × 0.5 m) quadrant randomly in 4 places in a plot. The growth parameters viz., plant height (cm), number of tillers and the yield attributes viz., the number of productive tillers, filled grains panicle^-1, grain yield (kg/ha) and straw yield (kg/ha) was recorded. For the observations related to weeds, a transformation of square root (√x+0.5) was applied to the values prior to performing analysis statistically to achieve normalization of their distribution. The statistical evaluation was conducted based on the mean values obtained. The statistical package used for analysis was R studio. A significance level of P = 0.05 was utilized for the ‘F’ and ‘t’ tests. Whenever the ‘F’ test was found to be significant, critical difference values were computed following the methodology described by Gomez and Gomez (1984).

Weed density
 
The total weed density was significantly reduced among the various weed control treatments. In the treatments, hand weeding twice at 20 and 40 DAS recorded the lowest weed density (5.38 no./m²) at 20 DAS. This was followed by PE Bensulfuron methyl + Pretilachlor @ 660 g/ha fb PoE Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha with 6.12 no./m². The highest weed density was observed in control with 12.30 no/m².
       
At the 40 and 60 DAS, PE Bensulfuron methyl + Pretilachlor @ 660 g/ha fb PoE Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha (Fig 6 and 7) consistently showed the least amount of weed density of 6.07 and 6.64 no./m², respectively. This shows the effectiveness of both pre-emergence and post-emergence herbicides for weed management. This was followed by EPoE Trifamone + Ethoxysulfuron @ 67.5 g/ha fb Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha (Table 1). Control plot recorded the highest weed density with 14.02 and 15.17 no/m² respectively (Fig 8). These findings correlate with Singh et al., 2018. Grasses were strong competitors, depleting a larger share of the available nutrients and leading over sedges and broad-leaved weeds (Suaganya, 2024). As pre-emergence application of bensulfuron methyl at less dosage found to be effective in controlling the broad leaves and sedges effectively. On other hand, application of pretilachlor at early stages reduces the grasses. Thus, pre mix combination of these chemicals-controlled weeds effectively (Negalur and Halepyati, 2016). The increased effectiveness of herbicides observed with drum seeding could be attributed to the quick emergence of weeds, during which the majority of these weeds were impacted by the herbicides (Singh and Singh 2010 and Mullaivendhan et al., 2024).








 
Weed control efficiency
 
The effectiveness of weed control (WCE) showed significant variations among the different treatments (Table 2). The highest WCE was obtained in treatment of hand weeding @ 20 and 40 DAS with 82.87%, which was closely followed by PE bensulfuron methyl + pretilachlor @ 660 g/ha fb PoE florpyrauxifen-benzyl + cyhalofop-butyl @ 150 g/ha with a WCE of 77.31%, indicating strong early-stage weed suppression achieved through manual or well-timed chemical interventions. In contrast, power weeding at 20 and 40 DAS showed the lowest weed control efficacy (WCE) at 46.36%, indicating that mechanical weeding alone has had limited effectiveness during this initial stage of crop growth.


       
In the final phases of crop development (40 and 60 DAS), PE Bensulfuron methyl + Pretilachlor @ 660 g/ha fb PoE Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha consistently achieved the most effective weed control hitting 83.04% at 40 DAS and 82.40% at 60 DAS (Table 3). EPoE Trifamone + Ethoxysulfuron @ 67.5 g/ha fb Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha on 25 DAS also showed high efficiency (76.65% and 74.99%), indicating that the consecutive use of both pre-and post-emergence herbicides had the efficient weed management. The consistent effectiveness of these treatments can be linked to the sequential use of herbicides aimed at various weed flushes, providing extended residual effects and minimizing weed competition over the season. These findings were in line with Hia et al. (2017) and Mullaivendhan et al. (2024). The greatest effectiveness in weed control was noted in plots treated with pre-emergence followed by post-emergence applications.


 
Crop growth and yield
 
Among the different treatments, applying PE Bensulfuron methyl + Pretilachlor @ 660 g/ha on fb PoE Florpyrauxifen-benzyl + Cyhalofop-butyl @ 150 g/ha on resulted in the taller plant height (78.80 cm), significantly outperforming all other treatments. The control plot had the shortest plant height at 57.40 cm. The combination of PE bensulfuron methyl + pretilachlor at 660 g/ha followed by PoE Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha also recorded the highest number of tillers (506/m²), with EPoE Trifamone + Ethoxysulfuron at 67.5 g/ha followed by Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha (473/m²). The control plot showed the lowest tiller count at 220/m², which was significantly lower than that of all other treatments. The highest number of grains per panicle was noted with the treatment of PE Bensulfuron methyl + Pretilachlor at 660 g/ha followed by PoE Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha (115.6), followed by EPoE Trifamone + Ethoxysulfuron at 67.5 g/ha followed by Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha (106.4). The control plot recorded the lowest grains, at 88.2. The higher grain output was attained through the use of PE Bensulfuron methyl + Pretilachlor at 660 g/ha followed by PoE Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha (5,550 kg/ha), which was notably higher than that of the other treatments. A yield of 5,128 kg/ha was also noted for EPoE Trifamone + Ethoxysulfuron at 67.5 g/ha followed by Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha, which also performed well. The control recorded the least yield at 1,246 kg/ha. Straw yield reflected a similar pattern, with PE Bensulfuron methyl + Pretilachlor at 660 g/ha followed by PoE Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha achieving the highest straw yield (7215 kg/ha), while EPoE Trifamone + Ethoxysulfuron at 67.5 g/ha followed by Florpyrauxifen-benzyl + Cyhalofop-butyl at 150 g/ha yielded 6720 kg/ha (Table 3). The control plot had the lowest straw yield at 2055 kg/ha. The presence of weeds adversely affected the growth and yield characteristics of the crop, ultimately leading to a decrease in the grain yield of direct-seeded rice (Saravanane, 2020 and Saravana Perumal et al., 2025). Lower weed density in the plots treated with chemicals enabled the crops to grow more effectively due to the reduced competition from weeds. Enhanced crop growth resulted from reduced competition for water, sunlight, nutrients and space in a weed-free setting. These findings align with the observations of Brar and Bhullar (2017) and Kaur and Singh (2015).

Efficient weed management is crucial for enhancing the yield of drum-seeded rice, particularly in situations with limited water and labor availability. Among the various methods evaluated, the sequential treatment of PE Bensulfuron methyl + Pretilachlor (660 g/ha) followed by PoE Florpyrauxifen-benzyl + Cyhalofop-butyl (150 g/ha) was the most effective in controlling weed density as well as increasing weed control efficiency. This approach also led to the greatest plant height, number of tillers, grain yield (5,550 kg/ha) and straw yield (7215 kg/ha). Ultimately, the integration of strategic herbicide applications provides a sustainable and profitable approach for managing weeds in drum-seeded rice.

All authors declared that there is no conflict of interest.