Effect of integrated weed management practices on growth, yield attributes, and economics of rice fallow sunflower (Helianthus annuus L.)

Introduction

Sunflower (Helianthus annuus L.) is one of the most important edible oilseed crops cultivated worldwide because of its high-quality oil, wide adaptability, and short duration. The seed contains 38-50% oil rich in unsaturated fatty acids, making it an important component of the human diet (Skoric et al., 2007) [14] . In India, sunflower contributes significantly to the edible oil sector and offers considerable scope for enhancing domestic oilseed production (Ramesh et al., 2019) [12] . India continues to face a substantial deficit in edible oil production despite being one of the world's leading oilseed-producing countries. During 2024-25, the country produced about 42.6 million tonnes of oilseeds, yet a large proportion of edible oil demand is met through imports (Government of India, 2025) [4] . Among oilseed crops, sunflower occupied approximately 0.15 million ha with a production of 0.11 million tonnes and productivity of about 750 kg ha⁻¹ during 2023-24, indicating substantial scope for productivity improvement (Directorate of Economics and Statistics, 2024) [3] . Rice-fallow lands constitute one of the largest untapped agricultural resources in India. Approximately 11.7 million hectares of rice-fallow area exist across the country, predominantly in eastern and central India (Ramesh et al., 2019) [12] . Productive utilization of these lands can significantly increase cropping intensity and oilseed production without expanding cultivated land area. Sunflower has emerged as a promising crop for rice-fallow situations because of its short duration, deep root system, drought tolerance, and ability to utilize residual soil moisture effectively (Kulasekaran et al., 2021) [6] . However, weed infestation remains one of the major constraints limiting sunflower productivity under rice-fallow conditions. Weeds compete with crops for moisture, nutrients, light, and space, particularly during the early stages of crop establishment, resulting in severe yield losses (Narendar & Narendar 2023) [9] .

Yield reductions ranging from 30 to 70% have been reported in sunflower due to uncontrolled weed growth depending on weed flora and crop-weed competition period (Nagamani et al., 2013) [7] Manual weeding and intercultivation are effective methods of weed control; however, their adoption is increasingly constrained by labour shortages and rising labour costs (Narendar et al., 2026) [8] . Herbicides offer timely and effective weed management, but sole dependence on herbicides may lead to herbicide resistance, weed flora shifts, and environmental concerns (Sai Satish et al., 2025) [13] . Therefore, sustainable weed management requires integration of chemical, cultural, and mechanical approaches. 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 (Parameswari et al., 2025) [11] . Several studies have demonstrated that integration of pre-plant, preemergence, 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) [1] Apart from reducing weed competition, effective weed management enhances nutrient uptake and nutrient-use efficiency by minimizing nutrient depletion by weeds and increasing nutrient availability to the crop (Narendar et al., 2026) [8] . Consequently, improvements in growth attributes, yield components, seed yield, and economic returns have been reported under integrated weed management systems compared with sole herbicide or manual weed control practices (Choudhary et al., 2022) [1] . Nath et al. (2024) [10] emphasized the need for diversified and integrated weed management approaches. In this context, IWM represents the most sustainable and environmentally responsible strategy for managing weeds in sunflower. Although several studies have evaluated individual weed management practices in sunflower, information on integrated weed management strategies under rice-fallow ecosystems remains limited. Therefore, the present investigation was undertaken to evaluate the effect of integrated weed management practices on growth, yield attributes, yield, and economics of rice-fallow sunflower (Helianthus annuus L.) and to identify an efficient and economically viable weed management strategy for sustainable sunflower production.

Materials and Methods

A field experiment entitled "Effect of Integrated Weed Management Practices on Growth, Yield Attributes, and Economics of Rice Fallow Sunflower (Helianthus annuus L.)" was conducted during summer 2022 at the Instructional Farm of Odisha University of Agriculture and Technology (OUAT), Bhubaneswar (20°27 1 N, 85°79 1 E; 25.9 m AMSL). The experimental soil was sandy loam in texture (73.8% sand, 14.1% silt, and 12.8% clay) with pH 5.12, medium available nitrogen (132.16 kg ha⁻¹), low available phosphorus (2.50 kg ha⁻¹), and high available potassium (262.30 kg ha⁻¹). The experiment comprised eight weed management treatments: T₁-paraquat before sowing + one intercultivation at 35 DAS; T₂-paraquat before sowing + pendimethalin (1.0 kg a.i. ha⁻¹, PE) + quizalofop-ethyl (37.5 g a.i. ha⁻¹, PoE at 20 DAS); T₃-pendimethalin (1.0 kg a.i. ha⁻¹, PE) + one intercultivation at 30 DAS; T₄pendimethalin (1.0 kg a.i. ha⁻¹, PE) + quizalofop-ethyl (37.5 g a.i. ha⁻¹, PoE at 20 DAS); T₅-two intercultivations at 20 and 40 DAS; T₆-one intercultivation at 20 DAS followed by one hand weeding at 30-35 DAS; T₇-weed-free; and T₈unweeded control. Sunflower was sown on 30 January 2022 and harvested on 2 nd May 2022. Pre-emergence herbicides were applied within 48 h of sowing, while post-emergence application was carried out at 20 DAS. All other agronomic practices were followed as per OUAT recommendations. Biometric observations were recorded from five randomly selected plants in each treatment and the mean values were subjected to statistical analysis.

Results and Discussions Effect of Weed Management Treatments on Plant Height

Plant height of sunflower was significantly influenced by weed management practices at all growth stages (Table 1). The weed-free treatment (T₇) consistently recorded the highest plant height at 30 DAS (39.8 cm), 60 DAS (148.3 cm), and harvest (159.3 cm), and was significantly superior to all other treatments. Among the weed management practices, two intercultivations (T₅) and one intercultivation followed by hand weeding (T₆) produced taller plants and ranked next to the weed-free treatment. Among the herbicide-based treatments, T₂ (paraquat + pendimethalin + quizalofop-ethyl) recorded greater plant height than T₁, T₃, and T₄. The unweeded control (T₈) consistently recorded the lowest plant height throughout the crop growth period. Enhanced plant height under effective weed management treatments may be attributed to reduced crop-weed competition and improved availability of nutrients, moisture, and light, whereas uncontrolled weed growth adversely affected vegetative growth and plant development. The results are in confirmatively with Tadavi et al., (2017) [15] . .

Effect of Weed Management Treatments on Number of Leaves per Plant Number of leaves at 30, 60 DAS and at Harvest

The number of leaves per plant was significantly influenced by weed management practices at all growth stages (Table 1). The weed-free treatment (T₇) consistently recorded the highest number of leaves at 30 DAS, 60 DAS, and harvest, followed by two intercultivations (T₅) and one intercultivation coupled with hand weeding (T₆), which remained statistically comparable. Among the herbicidebased treatments, T₂ (paraquat + pendimethalin + quizalofop-ethyl) produced a higher leaf count than T₁, T₃, and T₄. The unweeded control (T₈) recorded the lowest number of leaves throughout the crop growth period. Increased leaf production under effective weed management treatments may be attributed to reduced crop-weed competition and improved availability of growth resources, whereas unchecked weed growth restricted leaf initiation and development, resulting in lower leaf counts. The results are in agreement with Tadavi et al., (2017) [15] .

Effect of Weed Management Treatments on Leaf Area Index (LAI)

Leaf Area Index at 30, 60 DAS and at Harvest Leaf Area Index (LAI) Leaf Area Index (LAI), an important indicator of crop growth and photosynthetic efficiency, was significantly influenced by different weed management treatments throughout the crop growth period (Table 1). The weed-free treatment (T 7 ) consistently recorded the highest LAI, followed by two inter-cultivations (T 5 ) and one intercultivation followed by hand weeding (T 6 ), indicating the effectiveness of these practices in promoting canopy development. Among the herbicide treatments, T 2 maintained comparatively higher LAI values than T 1 , T 3 , and T 4 , suggesting better weed control and improved crop growth. In contrast, the unweeded control (T 8 ) recorded the lowest LAI at all growth stages due to intense weed competition for essential resources. LAI increased from 30 to 60 DAS as a result of active vegetative growth and declined towards harvest because of natural leaf senescence. However, treatments with effective weed management maintained higher LAI throughout the crop growth period. Overall, the results indicate that efficient weed control enhanced canopy development and sustained crop growth, resulting in improved photosynthetic potential [ (Nagamani et al., 2013); Kalaiyarasan et al., (2019)] [7,5]

Effect of Weed Management Treatments on Relative Growth Rate (RGR) Relative Growth Rate (RGR)

Relative Growth Rate (RGR), which reflects the efficiency of dry matter accumulation per unit of existing biomass, was significantly influenced by different weed management treatments throughout the crop growth period (Table 2). However, the variation among treatments was relatively narrow compared to other growth parameters. During the early growth stage, comparatively higher RGR values were observed in T 4 , T 8 , and T 3 , while the remaining treatments recorded similar values. As the crop advanced from vegetative growth to reproductive development, RGR declined progressively across all treatments. This reduction is a normal physiological phenomenon associated with crop maturation, as the rate of new biomass production decreases relative to the accumulated plant biomass. During the later growth stages, treatments such as T 1 , T 2 , T 5 , and T 6 maintained relatively higher RGR, whereas weed-free and mechanically managed treatments sustained marginally greater growth efficiency up to harvest. Despite these differences, the overall declining trend in RGR was evident across all treatments. The results indicate that while weed management practices influenced RGR to some extent, crop age had a greater effect on this parameter. The progressive decline in RGR from 30 DAS to harvest conforms to the well-established concept of ontogenic drift, where relative growth efficiency decreases as the crop matures. (Devendra Kumar 2015) [2]

Effect of Weed Management Treatments on Crop Growth Rate (CGR) Crop Growth Rate (CGR)

Crop Growth Rate (CGR), an important indicator of dry matter accumulation per unit area, was significantly influenced by different weed management treatments throughout the crop growth period (Table 2). Effective weed control generally enhanced CGR by improving resource availability and promoting better crop growth. The weedfree treatment (T 7 ) consistently recorded higher CGR values, particularly during the early and later stages of crop growth, followed by two inter-cultivations (T 5 ) and one inter-cultivation combined with hand weeding (T 6 ). Among the herbicide treatments, T 1 and T 2 exhibited comparatively higher CGR during the active vegetative phase, indicating efficient dry matter production under these treatments. In contrast, the unweeded control (T 8 ) generally recorded lower CGR, reflecting the adverse effects of weed competition on crop growth. CGR increased from 30 to 60 DAS across treatments, corresponding to the grand growth phase characterized by rapid canopy expansion and biomass accumulation. Thereafter, CGR declined towards harvest as the crop shifted from vegetative growth to reproductive development and grain filling. Nevertheless, weed-free and mechanically managed treatments maintained relatively higher CGR up to harvest, demonstrating their ability to sustain dry matter production throughout the crop growth period. Overall, the results highlight the importance of effective weed management in enhancing crop growth and biomass accumulation, thereby improving the productive potential of rice-fallow sunflower (Devendra Kumar 2015) [2] .

Effect of Weed Management Treatments on Economics of Sunflower Cultivation Economics

The economics of sunflower cultivation was markedly influenced by different weed management practices (Table 3). The cost of cultivation varied depending on the intensity and type of weed control measures adopted. The weed-free treatment (T 7 ) incurred the highest cost of cultivation due to repeated hand weedings, whereas the unweeded control (T8) recorded the lowest cost owing to the absence of weed management operations. Weed management practices significantly improved gross returns, net returns, and benefit-to-cost (B:C) ratio over the unweeded control. The highest gross returns (₹1, 29, 844 ha⁻¹), net returns (₹61, 641 ha⁻¹), and B:C ratio (1.90) were recorded under the weed-free treatment (T 7 ), reflecting its superior yield performance. Among the managed treatments, T 2 (paraquat + pendimethalin + quizalofop ethyl) emerged as a highly profitable option, recording gross returns of ₹1, 12, 200 ha⁻¹, net returns of ₹52, 277 ha⁻¹, and a B:C ratio of 1.87. Similarly, two inter-cultivations at 20 and 40 DAS (T5) also resulted in higher economic returns with a B:C ratio of 1.84. In contrast, the unweeded control (T8) recorded the lowest gross returns (₹50, 727 ha⁻¹), net returns (₹4, 876 ha⁻¹), and B:C ratio (0.91), indicating poor economic viability due to severe yield reduction caused by weed competition. Overall, effective weed management substantially enhanced the profitability of rice-fallow sunflower, with the weed-free treatment proving most remunerative, while T 2 offered a cost-effective and economically attractive alternative under practical farming conditions. The results are in line with Tadavi et al., (2017) [15] and Thambiyannan et al., (2024) [16] . Paraquat spray before sowing pendimethalin 1.0 kg a.i ha -1 as preemergence spray + Quizalofop ethyl 10EC @ 37.5 g ai ha -

Conclusion

The present investigation conclusively establishes that weed competition exerts a severe and economically devastating impact on rice fallow sunflower, significantly suppressing plant height, leaf number, leaf area index, stem girth, and crop growth rate at all stages of crop development. Among all treatments evaluated, the weed-free treatment consistently delivered the highest biological and economic performance; however, its dependence on repeated hand weeding makes it labour-intensive and less practical under large-scale farming conditions.The integrated herbicide treatment T 2 (paraquat spray before sowing + pendimethalin 1.0 kg a.i. ha⁻¹ as pre-emergence + quizalofop ethyl 37.

References

1. Choudary VK, Dubey RP, Mishra JS. Weed management in oilseed crops: A review. Indian J Weed Sci. 2022;54(4):411-420.
2. Dewangan DK. Effect of various moisture regimes, nutrient sources and weed management practices on growth, yield and weed dynamics of sunflower-rice cropping system [Ph.D. thesis]. Raipur: College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya; 2015.
3. Directorate of Economics and Statistics. Agricultural statistics at a glance. New Delhi: Government of India; 2024.
4. Government of India. Ministry of Agriculture and Farmers Welfare. Oilseed production statistics. New Delhi: Government of India; 2025.
5. Kalaiyarasan C, Vaiyapuri V, Suseendran K, Jawahar S. Response of sunflower to integrated nutrient and weed management practices on weeds, growth, yield, quality and nutrient uptake. Plant Arch. 2019;19(1):526-533.
6. Ramesh K, Mahapatra A, Roy A, Bhaskar S. Reviving horizontal area expansion of sunflower (Helianthus annuus L.) in rice fallow ecosystems: A relook. J Oilseeds Res. 2021;38(2).
7. Nagamani C, Muneendra Naidu SM, Subramanyam D. Nutrient uptake, yield and economics of rabi sunflower as influenced by plant density and weed management practices. Andhra Agric J. 2013;60(2):255-259.
8. Narendar G, Jannu N, Dash R, Kar I, Balairsingh A, Parameswari YS. Technological advances in weed management for suitable crop production. AMA Agric Mech Asia Afr Lat Am. 2026;57(1):21897-21908.
9. Jannu N, Narendar G. Weed management in direct seeded rice in Indian perspective: A review. Pharma Innov J. 2023;12(1):2522-2532.
10. Nath CP, Singh RG, Choudhary VK, Datta D, Nandan R, Singh SS. Challenges and alternatives of herbicidebased weed management. Agronomy. 2024;14(1):126.
11. Parameswari YS, Narendar G, Tejashree M, Krishna Chaitanya A. Optimizing weed control in onion cultivation for higher yield and returns: Techniques and effectiveness. AMA Agric Mech Asia Afr Lat Am. 2025;56(11):21575-21585.
12. Kumar R, Mishra JS, Upadhyay PK, Hans H. Rice fallows in eastern India: Problems and prospects. Indian J Agric Sci. 2019;89(4):567-577.
13. Sai Satish D, Narendar G, Mounika T, Prameela G. Innovations in agriculture-smart solutions for sustainable food production. 2025;8(6):1028-1033.
14. Skoric D, Jocic S, Lecic N, Sakac Z. Development of sunflower hybrids with different oil quality. Helia. 2007;30(47):205-212.
15. Tadavi AG, Chorey AB, Gaikwad GS, Swadhakar SM. Integrated weed management in sunflower. Int J Curr Microbiol Appl Sci. 2017;6(9):1080-1088.
16. Thambiyannan S, Lingan R, Ramasamy S, Ramasamy K, Rajendhiran N, Kaliyannagounder S, et al. Sustainable integrated weed control strategies to reduce herbicide use in sunflower production. Plant Sci Today. 2024;11(4):570-579.