Bio-efficacy of Different Herbicides against Cyperus spp. in Wet-Seeded Rice (WSR) and their Effect on Rice Growth Parameters

Abstract

Direct-seeded rice (DSR) is emerging as a promising alternative to conventional puddled transplanted rice due to its lower labour, water, and energy requirements. However, severe weed infestation, particularly by Cyperus rotundus and other sedges, remains a major constraint limiting productivity under DSR systems. A field experiment was conducted at the Faculty of Agriculture, Wadura, SKUAST-Kashmir, to evaluate the bio-efficacy of different herbicides against Cyperus spp. and their influence on rice growth parameters and economic returns. The experimental soil was slightly acidic (pH 5.9), medium in available nitrogen (327 kg ha⁻¹), phosphorus (17.3 kg ha⁻¹), and potassium (248 kg ha⁻¹), with high organic carbon content (0.98%). The study was laid out in a randomized block design with nine treatments, comprising various pre- and post-emergence herbicides along with weedy check and weed-free controls, each replicated thrice. The treatments included halosulfuron (75 WG) @ 35 g ha⁻¹, bensulfuron-methyl (60 DF) @ 60 g ha⁻¹, cyhalofop-butyl (10 EC) @ 100 g ha⁻¹, bispyribac-sodium (10 SC) @ 30 g a.i. ha⁻¹, ethoxysulfuron (15 WDG) @ 45 g ha⁻¹, pretilachlor @ 700 g ha⁻¹, and pendimethalin (30 EC) followed by 2,4-D (58 SL) (0.75 + 1.0 kg ha⁻¹). Results revealed that weed management treatments significantly influenced crop growth parameters, except at early growth stages. Among the herbicidal treatments, post-emergence application of bispyribac-sodium @ 30 g a.i. ha⁻¹ proved most effective in suppressing mixed weed flora, including sedges, grasses, and broad-leaved weeds. This resulted in significantly higher plant height, leaf area index (LAI), and dry matter accumulation compared to other treatments. The weed-free treatment recorded the highest growth values; however, it was less economical due to higher labour costs. Economic analysis indicated that bispyribac-sodium @ 30 g a.i. ha⁻¹ achieved the highest net returns and benefit–cost ratio (1.49), demonstrating superior economic efficiency among herbicidal treatments. In contrast, the weedy check recorded the lowest growth and economic performance due to severe crop–weed competition. Overall, the study highlights that appropriate selection and timely application of herbicides, particularly bispyribac-sodium, can effectively manage Cyperus spp. and associated weed flora, improve crop growth, and enhance economic returns, thereby contributing to sustainable rice production under labour- and water-limited conditions.