Optimizing weed management in summer sunflower (Helianthus annuus L.) in east and south eastern coastal plain zone of Odisha

Introduction

Sunflower (Helianthus annuus L.) is an important oilseed crop cultivated widely for its high-quality edible oil and nutritional value. The crop is valued for its oil rich in unsaturated fatty acids, particularly linoleic and oleic acids, besides containing proteins, vitamins (E, B, folate and niacin), minerals and antioxidant compounds (Petaru et al.,2021; Islam et al., 2016) [1,2] . In India, sunflower contributes significantly to the India's edible oil sector and offers considerable scope for enhancing domestic oilseed production (Ramesh et al., 2021) [3] . Globally, sunflower occupies an important position among edible oilseed crops, while in India it is cultivated over 1.94 lakh hectares with an annual production of around 2.36 lakh tones with an average productivity of 1214 kg ha -1 (Annual report, sunflower, 2025-26) [4] and predominantly grown in Karnataka, Andhra Pradesh, Maharashtra and Tamil Nadu, with increasing adoption in non-traditional sunflower-growing regions including Odisha. The crop also has considerable potential in Odisha because of its suitability for rabi and summer cultivation and its importance as a source of edible oil. Despite its adaptability and economic importance, sunflower productivity is considerably constrained by weed infestation (Adhikary et al., 2024) [5] . Weed problem in sunflower is considered a serious problem because weeds not only compete for water, nutrients, light and space but also serve as alternate host for several insect pests and diseases which reduce crop growth and yield (Sumathi et al., 2009; Pannacci et al., 2007) [6] . Hence, managing weed population below the economic threshold level is the basic need to optimize the productivity (Hatti et al., 2018) [7] . Manual weeding and intercultivation are effective methods of weed control widely practised in India; however, their adoption is increasingly constrained by labour shortages and rising labour costs. Herbicides offer timely and effective weed management, but sole dependence on herbicides may lead to herbicide resistance, weed flora shifts, and environmental concerns. Integrated Weed Management (IWM) has been recognized as an environmentally sound and economically viable strategy for maintaining weed populations below economic threshold levels while reducing dependence on any single weed control method (Swanton et al., 2008) [8] . Several studies have demonstrated that integration of pre-plant, pre-emergence, and post-emergence herbicides with mechanical weed control significantly improves weed suppression, crop growth, nutrient uptake, and yield in oilseed crops (Choudhary et al., 2022) [9] . However, the effectiveness and economic viability of a particular weed-management programme are strongly influenced by the prevailing weed flora, environmental conditions, crop variety and production system. Hence, location-specific evaluation of alternative combinations of pre-emergence, post-emergence, manual and mechanical weed-control practices is necessary. This is particularly relevant for sunflower production under the agro-ecological conditions of Odisha, where information on effective and economically feasible integrated weed-management schedules for sunflower remains comparatively limited. The study was therefore undertaken to identify an effective and economically viable weed-management strategy capable of minimizing cropweed competition, improving sunflower growth and productivity and increasing profitability under the summer growing conditions of Bhubaneswar.

Materials and methods

A field experiment was carried out at Instructional Farm of Odisha University of Agriculture & Technology (OUAT), Bhubaneswar during summer season of 2024-25. The soil of the experimental field was sandy loam in texture, slightly acidic (pH 6.05), medium in organic carbon (0.58%), low in available nitrogen (172 kg ha -1 ), medium in available phosphorous (22.5 kg ha -1 ) and low in available potassium (92.00 kg ha -1 ). The experiment was laid out in randomized block design with eight treatments and three replications viz, T 1pendimethalin 1 kg ha -1 as pre-emergence, T 2 -quizalofop-p-ethyl 5% EC @ 50g ha -1 as PoE at 18 DAS, T 3 -pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS, T 4 -quizalofop-p-ethyl 5% EC @ 50g ha -1 as PoE at 18 DAS fb one HW at 30 DAS, T 5pendimethalin 1 kg ha -1 as pre emergence fb quizalofop-p-ethyl 5%EC @ 50g ha -1 as PoE at 18 DAS, T 6 -two intercultivations at 20 and 40 DAS, T 7 -weed free (three HW at 15, 30 and 45 DAS) and T 8unweeded control. The management practice is kept constant for all the treatments except the weed management. Throughout the cropping periods, different species of weeds that were observed in the experimental field were recorded at a regular interval. At 30 DAS, 60 DAS and at harvest, the number of weeds in a square meter of each plot was counted. These weeds were than categorized into grasses, sedges and broad-leaved weeds, and their respective densities as well as total density were recorded. Dry weight of weeds was recorded at 30 DAS, 60 DAS and at harvest. The weeds were uprooted from the destructive sampling area of one square meter and were oven dried at 70 °C for obtaining a constant weight and the dry weight of weeds was expressed in g m -2 . Weed control efficiency was calculated by the help of formula given by Mani et al., 1973 [10] .

Where, X: Weed dry matter production in weedy plot Y: Weed dry matter production in treated plot.

Weed index indicates the extent of reduction in yield due to crop weed competition which was worked out for different treatments by adopting the formula given by Gill and Kumar,1969 [11] .

Weed index = 𝐴 -𝐵 𝐴 × 100

Where, A: Seed yield of the weed free treatment, B: Seed yield of the particular treatment for which the index is computed. LAI is the ratio between leaf area to ground area and is calculated by the following formula:

Total leaf area is calculated by multiplying the actual leaf area per plant with number of plants per m 2 . Crop growth rate indicates the increase in dry weight of plant per unit area of land per unit change in time and expressed as g d -1 m -2 and is calculated by the formula:

Where, W 1 and W 2 are dry matter at times t 1 and t 2 respectively, and P is land area. The oil content in seed for each treatment plot was estimated by using Nuclear Magnetic Resonance (NMR) spectrometer (Tiwari et al., 1974) [12] . The oil yield (kg ha -1 ) was calculated based on seed yield (kg ha -1 ) and corresponding oil content (%).

Results and discussion

Weed flora

The most common weeds (grasses, sedges, and broadleaves) associated with the sunflower crop found in the experimental field are listed in Table1. [14,13,15] .

Weed density

Grass population was significantly influenced by weed management treatments. Lowest grass population was found in weed free treatment at 30 DAS (4.38 m -2 ), 60 DAS (5.33m -2 ) and at harvest (6.28m -2 ) and highest weed population was found in weedy check treatment (8.35m -2 , 9.26m -2 ,10.35m -2 at 30, 60 DAS and at harvest respectively. The sedge population was lowest in weed free treatment (three hand weeding at 15, 30 and 45 DAS) at 30 DAS, 60 DAS and harvest (3.29m -2 , 3.98m -2 , 5.37m -2 respectively) followed by pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS (3.97 m -2 , 4.70 m -2 , 5.68 m -2 respectively). Weed free treatment recorded lowest broad leaf weed population throughout the growth stages. At harvest the lowest broadleaf weeds were found in weed free treatment (6.52 m -2

) followed by pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS (7.37 m -2 ). Throughout the growth period of the crop, weedy check treatment has shown highest number of broad leaf populations (8.17m -2 , 9.17m -2 and 10.78m -2 at 30, 60 DAS and at harvest respectively). The total weed population at 60 DAS was lowest in weed free (8.65m -2 ) followed by the treatment two intercultivations at 20 and 40 DAS (10.17m -2 ) which was found at par with pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS (10.40m -2 ). At harvest stage, weed free treatment showed lowest number of total weed population (10.48/m 2 ) followed by pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS (11.38m -2 ). Throughout the crop growth stage, highest numbers of weeds were found in Weedy check. This can be attributed to efficiency of manual weeding in reducing weed populations (Meti et al., 2016; Tripathy et al., 2026) [15] .

Dry weight of weeds

Weed dry weight increased from initial growth stage to harvest stage and was significantly affected by different weed management practices. At 30 DAS, weed dry weight per square-meter was minimum in Weed free (2.78 g m -2

) followed by the treatment two intercultivations at 20 and 40 DAS (3.76g m -2 ). The highest weed dry weight was found in weedy check (8.70g m -2 ). At 60 DAS, lowest weed dry weight was found in Weed free (3.81g m -2 ) followed by pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS(4.60g m -2

) which is at par with two intercultivations at 20 & 40DAS (4.80 g m -2 ), whereas highest weed dry weight was found in weedy check (10.50 g m -2 ). At harvest, weed free treatment gave lowest weed dry weight (4.51 g m -2 ) followed by pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS (5.27g m -2

) which was at par with the treatment two intercultivations at 20 and 40 DAS (5.61g m -2 ) (Shylaja et al., 2008; Mahapatra et al., 2025a) [17,16] .

Weed control efficiency (WCE) and weed index (WI)

The weed free treatment showed higher weed control efficiency throughout the growth stages as the weeds are controlled in a timely, effective manner. At 30 DAS, the next best WCE was found in the treatment two intercultivations at 20 and 40DAS whereas at 60 DAS and at harvest pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS resulted in better WCE than two intercultivations at 20 and 40DAS, which was closely followed by pendimethalin 1 kg ha -1 as pre-emergence fb quizalofop-p-ethyl 5% EC @ 50g ha -1 as PoE at 18 DAS. This can be attributed to mechanical weeding at early stage which help in reducing initial weed load, but application of herbicide followed by one hand weeding or application of one pre-emergence herbicide followed by one post-emergence herbicide that help in preventing weeds which escape the pre-emergence herbicide or emerged later provide a long term weed control, thus improving WCE at later growth stages (Shylaja and Sundari, 2008; Nagmani et al.,2011) [18,17] . After weed free treatment, the lowest WI was observed in pendimethalin 1 kg ha -1 as PE fb one HW at 30 DAS (5.81 %) followed by two intercultivations at 20 & 40 DAS (6.79%) fb pendimethalin 1 kg ha -1 as pre-emergence fb quizalofop-p-ethyl 5% EC @ 50g ha -1 as PoE at 18 DAS (7.98 %) (Selvakumar et al., 2018, Mahapatra et al.,2024a, Mahapatra et al., 2025b) [14] .

Growth and yield

Growth parameters were significantly influenced by weed management treatments. The highest plant height (175 cm) at harvest, stem girth (8.1 cm), LAI (3.02) at 60 DAS, dry weight (111.0g plant -1 ) at harvest and CGR (17.92 g day -1 m -2 ) was observed with the weed free treatment and the lowest values for all the growth parameters were observed with weedy check. After weed free, the treatments, pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS, pendimethalin 1 kg ha -1 as pre-emergence fb quizalofop-p-ethyl 5% EC @ 50 g ha -1 as PoE at 18 DAS and two intercultivations at 20 and 40 DAS remained statistically at par with respect to plant height, stem girth, LAI, dry weight of plant and CGR. This can be attributed to timely weed management by intercultivations or both pre-emergence and post-emergence herbicides, which helps in hindering nutrient and moisture uptake by weeds, leading to robust growth of the crop whereas poor weed management, as reflected in the weedy check, resulted in stunted plant growth (Karkanis et al., 2022; Mahapatra et al., 2024b) [19,20] . The highest seed yield was obtained with weed free (1858 kg ha -1 ), which remained at par with pendimethalin 1 kg ha -1 as pre-emergence fb one HW at 30 DAS, pendimethalin 1 kg ha -1 as pre-emergence fb quizalofop-p-ethyl 5% EC @ 50 g ha -1 as PoE at 18 DAS and two intercultivations at 20 and 40 DAS. The lowest seed yield (834 kg/ha) was recorded in weedy check. The highest seed yield in the weed free treatment may be due to regular manual weeding that helped in removal of all weed flushes, minimizing competition throughout the crop's growth cycle. While weed free yields the best results, integrated weed management practices, especially those com-bining pre-emergence herbicides with either manual or post-emergence interventions, are nearly as effective and more feasible for large scale operation (Nagamani et al.,2011; Baskaran and Kavimani, 2014; Narender et al.,2017) [18,21,22] . Stover yield varied from 2438 to 3938 kg ha -1 among the treatments. The highest stover yield (3938 kg ha -1 ) was recorded with pendimethalin 1 kg ha -1 as preemergence followed by one hand weeding at 30 DAS, closely followed by weed-free with 3934 kg ha -1 . Two intercultivations at 20 and 40 DAS and pendimethalin 1 kg ha -1 as pre-emergence fb quizalofop-p-ethyl 5% EC @ 50 g ha -1 as PoE at 18 DAS recorded 3868 and 3781 kg ha -1 , respectively. The lowest stover yield (2438 kg ha -1 ) was recorded under the weedy check . The greater stover production under effective weed control can be attributed to reduced weed competition, which allowed sunflower plants to utilize available nutrients, moisture, light and space more efficiently, resulting in greater vegetative growth and dry-matter accumulation (Sumathi et al., 2010; Narender et al., 2017) [23,22] . Harvest index ranged from 25.3 to 32.2%. The highest harvest index (32.2%) was recorded in T 7 (weed-free), followed by T 6 (31.3%), T 5 (31.1%) and T 3 (30.8%). The lowest harvest index (25.3%) was observed under the weedy check. The relatively high harvest index under T 5 , T 6 and T 3 also indicates efficient translocation and partitioning of assimilates towards seed formation. In contrast, severe weed competition under weedy check restricted crop growth and reduced seed production, resulting in a lower harvest index (Meti et al., 2017) [24] . Oil yield showed a clear response to weed management and ranged from 307 to 697 kg ha -1 . The maximum oil yield (697 kg ha -1 ) was recorded under T 7 (weed-free), followed by T 3 (656 kg ha -1

), T 6 (646 kg ha -1 ) and T 5 (638 kg ha -1 ). The minimum oil yield (307 kg ha -1 ) was recorded under the weedy check. The substantially higher oil yield under effective weed management was mainly associated with higher seed yield, as oil yield is directly influenced by seed production and oil content (Parmar et al., 2014; Tadavi et al., 2017; Mahapatra et al., 2025b) [25,26,13] .

Economics

Weed-management practices considerably influenced the economics of sunflower cultivation. The cost of cultivation ranged from ₹61,304 ha -1 under the weedy check (T 8 ) to ₹75,384 ha -1 under the weed-free treatment (T 7 ). The highest gross return (₹1,35,279 ha -1 ) was obtained with weed free(T 7 ), followed by T 3 (₹1,27,424 ha -1

), T 6 (₹1,26,090 ha -1 ) and T 5 (₹1,24,488 ha -1

). The highest net return of ₹59,895 ha -1 was recorded under weed free(T 7 ), closely followed by T 5 (₹58,916 ha -1 ) and T 3 (₹57,520 ha -1 ). However, the B:C was highest under T 5 (1.90), followed by T 3 (1.82) and T 6 (1.80), whereas, weed free (T 7 recorded a B:C ratio of 1.79. The relatively lower B:C ratio under weed free(T 7 ) despite its higher gross and net returns, was due to the greater cost involved in three hand weedings. In contrast, pendimethalin 1 kg ha -1 as pre-emergence fb quizalofopp-ethyl 5% EC @ 50 g ha -1 as PoE at 18 DAS recorded higher B:C due to lower cost of cultivation, resulting in a higher B:C. The weedy check recorded a negative net return (-₹589 ha -1 ) and a B:C ratio of only 0.99, indicating that uncontrolled weed competition substantially reduced the economic viability of sunflower cultivation (Parmar et al.,2014 and Tadavi et al.,2017, Mahapatra et al., 2025a&b) [25] .

Conclusion

Weed management had a pronounced influence on growth, productivity and economic returns of sunflower. Weed-free (three hand weedings at 15, 30 and 45 DAS) sunflower resulted in lowest weed density, dry weight, highest weed control efficiency, plant height, leaf area index, stem girth, dry matter accumulation, crop growth rate, seed yield (1858 kg ha -1 ), harvest index (32.2%), oil yield (697 kg ha -1 ), gross return (₹1,35,279 ha -1 ) and net return (₹59,895 ha -1 ). However, the higher cost associated with repeated hand weeding resulted in a B:C of 1.79. Sequential application of pendimethalin 1 kg ha -1 as pre-emergence fb quizalofop-p-ethyl 5% EC @ 50 g ha -1 as PoE at 18 DAS resulted in high sunflower productivity with the high est B:C (1.90), which can be adopted in case of large-scale sunflower farming.

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30. How to cite this article: Mahapatra A, Patra J, Nayak BR, Bhandari A, Das SS, Mohanty S. Optimizing weed management in summer sunflower (Helianthus annuus L.) in east and south eastern coastal plain zone of Odisha. International Journal of Research in Agronomy. 2026;9(9):1119-1126. doi: https://www.d oi.org/10.33545/2618060X.2026.v9.i9o.6657