Optimization of weed management measures for enhanced growth and profitability of summer sesame in red and lateritic soils of West Bengal

Introduction

India still is one of the largest vegetable oil importing countries. The oil extracted from oilseeds forms an important item of human diet. Oilseeds are the source of energy and nutrition. India is among the largest vegetable oil economies in the world next only to USA and China. The country has launched a promising national scheme on oilseeds named, "National Food Security Mission on Oilseeds and Oilpalm (NMOOP)" to meet the demand and supply gap in edible oil production in the country (Mathur et al., 2023) [8] . Amongst oilseeds, sesame (Sesamum indicum L.) plays a vital role in meeting oilseed production due to its quality oil and protein rich seeds. It is also a successful rainfed crop with resilience to drought and adaptability to diverse agro-climatic conditions. Farmers of states like West Bengal, grow sesame as a major oilseed crop and its cultivation contributes significantly to the state's agricultural economy (Debnath et al., 2022) [3] . The red and lateritic soils of West Bengal pose a set of challenges for sesame cultivation due to poor nutrient retention capacity, low water-holding capacity and high susceptibility to erosion in such soils (Ghosh, 2019) [5] . This necessitates development of specialized agricultural practices to optimize crop production and productivity. Despite these challenges, sesame remains a promising crop for farmers in these regions due to its climate resilience and potential for high benefit to cost ratio. However, weeds in sesame result in extreme crop losses if not managed properly (Dawar et al., 2025) [2] . This is due to severe crop-weed competition for soil nutrients, moisture, space and light under the given agro-climate and poor soil conditions. Thus, development of research based effective, efficient and replicable integrated weed management strategies is pivotal for not only enhancing sesame productivity and production but also ensuring sustainable development agriculture through reduced reliance on chemical herbicides that can cause harmful damage to environment in these areas. While various weed management approaches have been studied in different crops, there is a knowledge gap regarding effective weed management tactics in summer grown sesame in red and lateritic soil of West Bengal. There is a need for location-specific research to develop effective weed management strategies that account for regional soil characteristics, climate, and crop-specific requirements (Fatima et al., 2020) [4] . Investigating the performance of summer sesame under diverse weed management practices in this region could help lakhs of farmers of the region to sustain their livelihood thorough improvement in sesame production and productivity. It would also help the policymakers to adopt and enact more productive and environmentally friendly practices. The current study aims to assess the efficacy of different weed management practices on summer sesame in West Bengal's red and lateritic soils and to find the most effective weed management approach.

Materials and Methods

A field experiment was carried out during summer 2019 in the Agricultural Farm, Institute of Agriculture (PSB), Visva-Bharati, Sriniketan, West Bengal characterised by tropical savanna climate. The experiment was laid out in a randomized block design with eight treatments and three replications. The weather parameters and soil conditions were suitable for growth of the sesame. The treatments comprised pendimethalin 750 g ha -1 as PE (T₁), butachlor 1000 g ha -1 as PE (T₂), pendimethalin 750 g ha -1 as PE fb HW at 30 DAS (T₃), butachlor 1000 g ha -1 as PE fb HW at 30 DAS (T₄), hand weeding at 15 DAS (T₅), hand weeding at 15 and 30 DAS (T₆), weed free check (T₇) and weedy check (T₈). The sesame variety, Rama was sown on 4 th March, 2019 @ 7.5 kg ha -1 in rows 30 cm apart with continuous sowing in rows. After sowing, the rows were covered with soils. The fertilizers were applied at the recommended dose of 80, 40 and 40 kg ha -1 of N, P₂O₅ and K₂O, respectively through Urea, SSP and MOP, respectively. Half of total N along with full dose of P₂O₅ and K₂O were applied basal at final land preparation and rest half of N was applied at 30 DAS (days after sowing), just before first irrigation. The crop was harvested on 4 th June, 2019. All other recommended package of practices were followed uniformly in all the plots except weed management practices which were applied as per the treatments of the experiment. The herbicidal treatments viz., pendimethalin @ 750 g ha -1 and butachlor @ 1000 g ha -1 were applied at 3 DAS as PE before the emergence of weeds in the field. Spraying of the herbicides was done at 4 pm (congenial time with maximum stomatal openings for quick transportation of herbicidal molecules into the plant system) with manually operated knapsack sprayer fitted with flat fan nozzle. Weeds were manually uprooted and removed from the plots in case of hand weeding. In case of weed free treatment, five hand weedings were done. The weed count/ population and dry matter of different categories of weeds were recorded separately at 30 and 60 DAS. The weed population was recorded by counting the number of weeds using a quadrate of 0.5 m x 0.5 m and were converted to population m -2 . For recording dry matter, these weeds were removed separately category wise, cleaned thoroughly, sun dried initially and then oven dried at 65 °C for 72 hours till constant weight was obtained. The data on weed population and dry matter were subjected to statistical analysis after square root transformation with the formula, √ (X + 0.5) before statistical analysis. Weed index is the measure of the efficiency of a particular treatment when compared with a weed free treatment. It is expressed as percentage of yield potential under weed free. Higher weed index means greater loss. Weed Index was calculated using the following formula:

Weed Index (%) = Yield from weed free plot -Yield from treated plot Yield from weed free plot × 100

The plant height, number of branches per plant, dry matter accumulation of the plants were recorded at harvest from five plants randomly selected for each plot. Net return is obtained by subtracting cost of cultivation from gross return.

Results and Discussion

Weeds Different categories of weeds infested the experimental field of sesame and are presented in Table 1. Similar observation was reported by (Ambika & Sundari, 2019) [1] . The lowest population of all categories of weeds was noticed in weed free treatment whereas, the weedy check treatment recorded the highest population at both 30 and 60 DAS (Table 2). At 30 DAS, hand weeded plots (T₅ and T₆) were at par and recorded significantly lower population of grass, sedge and broadleaved weeds than pendimethalin and butachlor treated plots (T₁ to T 4 ) but the herbicides could not lower the population of sedges significantly than weedy check (T 8 ). However, these herbicides were found effective against grasses and broadleaved weeds. T 3 was statistically at par with T 5 regarding broadleaved weed population. At 60 DAS, T₃, T₄ and T 6 , where one more hand weeding was done at 30 DAS, were at par and significantly reduced the population of grasses, sedges and broadleaved weeds than T₁, T₂ and T₅. Similar observation was reported by Singh et al., 2018 [11] . Sole application of pendimethalin and butachlor (T 1 and T 2 ) failed to reduce the sedge weed population than weedy check. According to the data recorded at 30 and 60 DAS, weed free (T₇) recorded the minimum dry weight of all categories of weeds and weedy check (T₈) resulted the maximum values. At 30 DAS, T₅ and T₆, where one hand weeding was done at 15 DAS, were statistically at par and recorded significantly lower dry weight of grasses, sedges and broadleaved weeds than the herbicide treated plots (T₁, T₂, T₃ and T₄). The dry weight of sedges was not significantly reduced by the application of the preemergence herbicides, pendimethalin and butachlor (T₁ to T₄). However, at 60 DAS T₃ and T₄, where one hand weeding was carried out at 30 DAS after pre-emergence application of pendimethalin and butachlor, respectively, were at par with T 6 (two hand weedings at 15 and 30 DAS) and recorded significantly lower dry weight of all categories of weeds than the sole application of the herbicides (T₁ and T₂). Kamini were also of the similar observations. The dry weight of sedges was not reduced significantly by the sole application of pendimethalin and butachlor as preemergence over weedy check.

Crop growth and economics

The lowest plant height, number of branches plant -1 , dry matter accumulation and net return was observed under weedy check. It might be due to severe crop-weed competition between weeds and sesame crop for growth resources. The highest values of plant height, number of branches plant -1 and dry matter accumulation these parameters were recorded by the weed free treatment which did not vary significantly from pendimethalin @ 750 g ha -1 as PE fb HW at 30 DAS, butachlor @ 1000 g ha -1 as PE fb HW at 30 DAS and hand weeding at 15 and 30 DAS.

Integrating of one hand weeding at 30 DAS after preemergence application of the herbicides, pendimethalin (T₃) and butachlor (T₄) or hand weeding at 15 DAS (T₆) resulted the higher growth parameters than their sole or single application (T 1 , T 2 and T 5 ). All the weed management treatments significantly increased the growth parameters than weedy check. It might be due to controlling weeds effectively and thereby making growth resources more available to the sesame crop. This corroborates with the findings of Rekhasree, et al., 2025 [9] . Uncontrolled weed growth resulted yield reduction of summer sesame by 62.66% (Table 4). The lowest weed index was found under pendimethalin @ 750 g ha -1 as PE fb HW at 30 DAS (8.27%) which was closely followed by hand weeding at 15 and 30 DAS (10.74%) and butachlor @ 1000 g ha -1 as PE fb HW at 30 DAS (12.92%). Weeds resulted 19.79, 26.94 and 37.15% yield loss in summer sesame in the treatments receiving pendimethalin and butachlor or hand weeding at 15 DAS i.e., T 1 , T 2 and T 5 , respectively. Similar results were revealed by Mane et al., 2017 [7] . The lowest net return was observed under weedy check (Rs.9348 ha -1 ). The highest net return was recorded by sole application of pendimethalin 750 g ha -1 as PE (Rs. 43570 ha -1 ) which was statistically at par with T 2 , T 3 and T 4 but was significantly higher the treatments where hand weeding was used for weed management in summer sesame (T 5 , T 6 and T 7 ). Similar findings were obtained by Sangeetha et al., 2019 [10] .

Conclusion

It may be concluded from the experiment that sole application of pendimethalin as pre-emergence is promising for effective and more remunerative weed management of summer grown sesame in the red and lateritic soil of West Bengal, India.

References

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