Influence of Chemical Weed Management Strategies on Enhancing Growth and Yield of Quinoa

This study evaluated the effect of herbicidal treatments on growth components, weed dynamics and yield in quinoa through a pot experiment conducted during the rabi season 2025 at the Instructional North Farm of Karunya Institute of Technology and Sciences, Coimbatore. The experiment followed a Completely Randomized Design (CRD) with twelve treatments and three replications, comparing different pre-emergence herbicides alone and in combination with post-emergence herbicides, along with weed-free check and unweeded control treatments. The results indicated that crop growth attributes varied significantly between treatments at later growth stages. At 30 DAS, the weed-free check (T11) recorded the highest plant height (39.28 cm), which was statistically similar to pretilachlor at 750 g a.i. ha-1 applied as pre-emergence (T3) and butachlor (pre-emergence) @ 1000 g a.i. ha-1 at 3 DAS + Metamifop @ 1000 ml ha-1 as post-emergence at 25 DAS (T9). At 60, 90 DAS and at harvest, the weed-free check (T11) consistently recorded superior plant height (95.3, 136.0 and 158.9 cm) and dry matter production (18.9, 27.9 and 36.2 g plant-1). Among the treatments sequential application of pretilachlor (pre-emergence) @ 750 g a.i. ha-1 at 3 DAS + halosulfuron-methyl (post-emergence) @ 70 g a.i. ha-1 at 25 DAS (T10)  recorded lower total weed density (2.38, 8.74, and 8.46 nos. pot-1), total weed dry weight (0.54, 4.86 and 4.19 g pot-1) and higher weed control efficiency (78.32%, 68.79% and 74.96%) at 15, 30 and 45 DAS, respectively. The weed-free check(T11) produced higher grain (39.5 g plant-1) and straw yields (45.05 g plant-1), which were statistically comparable to pretilachlor (pre-emergence) @ 750 g a.i. ha-1 at 3 DAS + halosulfuron-methyl (post-emergence) @ 70 g a.i. ha-1 at 25 DAS (T10). In contast, the unweeded control (T12) recorded the highest total weed density and weed dry weight, reduced crop growth and yield due to severe crop-weed competition. This study suggests that the sequential application of pretilachlor followed by halosulfuron-methyl has potential for effective weed management in quinoa under controlled conditions; however, further validation through field experiments is necessary before making broader agronomic recommendations.