International Journal of Environment and Climate Change

Direct-seeded rice is vulnerable to early-season weed competition, making effective pre-emergence weed management important for crop growth, grain yield and soil nutrient status.  A field study was conducted at the College of Agriculture, V. C. Farm, Mandya, Karnataka, during the Kharif season of 2021. The experiment was laid out in a randomised block design comprising nine treatments, viz.: T1: Pretilachlor 30% + pyrazosulfuron ethyl 0.75% WG @ 1500, g ha^-1 at 0-3 DAS, T2: Pretilachlor 30% + pyrazosulfuron ethyl 0.75% WG @ 2000, g ha^-1 at 0-3 DAS,  T3: Pretilachlor 30% + pyrazosulfuron ethyl 0.75% WG @ 2500, g ha^-1 at 0-3 DAS, T4: Pyrazosulfuron ethyl 10% WP @ 250 g ha^-1 at 3-5 DAS, T5: pretilachlor 50% EC @ 1500 ml ha^-1 at 0-5 DAS, T6: Pretilachlor 30% EC + 10% safener @ 1000 ml ha^-1 at 3-5 DAS, T7: hand weeding (20 & 40 DAS), T8: weedy check (control), and T9: weed-free check. The experiment was replicated three times on sandy loam soil to investigate the effect of various pre-emergence herbicides on growth attributes such as plant height, leaf area, tiller count and dry matter production in direct-seeded rice. The results indicated that, among the chemical weed management treatments, pretilachlor 30% + pyrazosulfuron ethyl 0.75% WG @ 2500 (g ha^-1 ) at 0-3 DAS (T3) recorded higher plant height (25.49, 47.11, 72.13 and 78.93 cm), number of tillers per metre row length (72.20, 170.52, 248.17 and 208.30), leaf area per metre row length (1293.70, 3190.9, 7927.0 and 2665 cm² per m row length), total dry matter production per metre row length (6.58, 91.24, 226.35 and 607.60 g per m row length) at 30, 60, 90 DAS and at harvest, respectively. These results were statistically comparable with those of the (T₉) weed-free check and (T₇) hand-weeding treatment at 20 & 40 DAS. The same treatment recorded a higher grain yield (6491 kg ha^-1) and straw yield (9584 kg ha^-1), which were comparable with those under hand weeding and the weed-free check. Post-harvest soil pH, EC and organic carbon were not significantly affected by the weed management practices. However, available N, P₂O₅ and K₂O were significantly influenced by the treatments. The study indicated that pretilachlor 30% + pyrazosulfuron ethyl 0.75% WG @ 2500 g ha^-1 applied at 0-3 DAS was an effective pre-emergence mixture for improving growth and productivity while maintaining favourable post-harvest soil nutrient availability in direct-seeded rice.