Integrated weed management in rabi sunflower (Helianthus annuus L.)

Abstract

The field experiment was conducted during the rabi season of 2020-21 at the Experimental Farm of the Agronomy Section, Oilseed Research Station, Latur, with the objective of evaluating integrated weed management practices in rabi sunflower (Helianthus annuus L.). The experimental soil was clay loam in texture with a neutral reaction (pH 7.02), moderate organic carbon content (0.30%), very low available nitrogen (231 kg ha⁻¹), low available phosphorus (8.57 kg ha⁻¹), and very high available potassium (580 kg ha⁻¹). The experiment was laid out in a Randomized Block Design comprising three replications and seven weed management treatments: T₁ - unweeded control; T₂ - one hand weeding at 20 DAS followed by one hand hoeing at 30 DAS; T₃ - three hand weedings at 15, 30, and 45 DAS; T₄ - Propaquizafop 10% EC @ 62 g a.i. ha⁻¹ applied at 20 DAS (post-emergence); T₅ - Propaquizafop 10% EC @ 62 g a.i. ha⁻¹ at 20 DAS (POE) combined with one hand weeding at 35 DAS; T₆ - Quizalofop-ethyl 10% EC @ 40 g a.i. ha⁻¹ at 20 DAS (POE); and T₇ - Quizalofop-ethyl 10% EC @ 40 g a.i. ha⁻¹ at 20 DAS (POE) along with one hand weeding at 35 DAS. Each experimental plot measured 5.4 m × 4.8 m (gross) with a net plot size of 4.2 m × 4.2 m. Sowing was carried out on 13 November 2020 using the dibbling method at a spacing of 60 cm × 30 cm. The recommended dose of fertilizers (90:45:45 kg NPK ha⁻¹) was applied, with half of the nitrogen and the full dose of phosphorus and potassium applied as basal, while the remaining nitrogen was top-dressed at 30 DAS. The crop was harvested on 17 February 2021. The results of the field experiment revealed that the weed-free treatment (T₃) recorded significantly superior growth and yield attributes, including plant height (195.54 cm), number of functional leaves per plant (24.85), leaf area per plant (73.95 dm²), stem girth (9.54 cm), head diameter (20.92 cm), and dry matter accumulation per plant (114.69 g), compared to all other treatments. Higher yield parameters such as number of filled seeds per plant (731), seed yield per plant (41.11 g), seed yield per hectare (2047 kg), and 100-seed weight (6.22 g) were also observed under weed-free conditions. However, these values were statistically comparable with treatments T₇, T₅, and T₂. The maximum net monetary returns (₹47,612 ha⁻¹) and benefit-cost ratio (2.29) were obtained with the application of Quizalofop-ethyl 10% EC @ 40 g a.i. ha⁻¹ at 20 DAS (POE) followed by one hand weeding at 35 DAS (T₇). Among the chemical weed management practices, treatment T₇ also resulted in the lowest weed index and dry weed biomass, along with the highest weed control efficiency.