Integrated Weed Management (IWM) for sunflower (Helianthus annuus L.) under modified spacing

The interaction between modified spacing and Integrated Weed Management (IWM) practices on weed dynamics, crop competitiveness and yield remains inadequately understood in sunflower cultivation particularly under diverse agro-ecological conditions. This gap necessitates systematic evaluation to develop spacing-specific IWM strategies for sustainable sunflower production. In the view of this, a three-year field study was conducted to evaluate the effectiveness of IWM practices on weed control, yield and soil health management of sunflower (Helianthus annuus L.) under modified spacing (75 cm × 25 cm) during the Rabi seasons (2021-22, 2022-23, 2023-24) at the Regional Agricultural Research Station (RARS), Nandyal, Andhra Pradesh. The study was carried out using the hybrid NDSH 1012 to assess the long-term impacts of weed management strategies on crop performance and sustainability. The experiment, laid out in a randomized block design (RBD) with seven treatments which includes integrated pre- and post-emergence herbicides, mechanical weeding, hand weeding and a weedfree check. The weed-free treatment (three hand weedings at 15, 30 and 45 days after sowing (DAS) recorded the lowest weed count (0.71-2.70 m-2), highest weed control efficiency (WCE: 89.0-98.7 %) and maximum seed yield (2307 kg ha-1). Pre-emergence pendimethalin (1.0 kg active ingredient ha-1) followed by one power weeding with inter-row rotary power weeder at 35 DAS recorded 2216 kg ha-1 comparable to the weedfree check, with 77.2-90.2 % WCE and weed index (WI) of 4.9-10.1 %. Farmer’s practice (two inter-cultivations + one hand weeding) recorded 2120 kg ha-1 with the highest net returns of ₹ 97595 ha-1 due to reduced labour cost. Soil microbial populations were unaffected by the treatments, indicating biological sustainability. Integrated weed management involving pendimethalin application with mechanical weeding is recommended as a cost-effective and eco-friendly weed control strategy for paddy-fallow sunflower cultivation in semi-arid India. This approach supports sustainable weed management while significantly reducing dependence on manual labour.