Presumption of Herbicide Resistant Weeds and Yield of Boro Rice as Influenced by Pre- and Post-emergence Herbicides

In Bangladesh, weed infestation is a leading problem in rice cultivation and the sole dependency on post-emergence herbicides is ineffective. Therefore, a field experiment was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh from December 2021 to May 2022. The study was done to determine the relative effectiveness of different pre-emergence herbicides and to presume the herbicide-resistant weeds and yield of boro rice as influenced by pre-and post-emergence herbicides. Four rice varieties: BAU dhan3 (V1), BRRI dhan28 (V2), BRRI dhan81 (V3), BRRI dhan96 (V4) and six herbicide managements: Control (H1), Hand Weeding at 30 DAT (H2), Bensulfuron methyl @ 980 g ha-1 (H3), Pretilachlor @ 2 L ha-1 (H4), Carfentrazon ethyl @ 208 mL ha-1 (H5), Ethoxisulfuron @ 200 g ha-1 (H6) were used in a randomized complete block design (RCBD) with three replications. The most dominant weed species in the experimental plots were Echinochloa crussgalli, Scirpus mucronatus, Monochoria hastata, Enhydra fluctuans and Oxalis europaea. This study found Ethoxisulfuron (H6) and Carfentrazon ethyl (H5) were the most effective weed management treatments for weed suppression and grain yield at twice the recommended doses. In this study, the highest grain yield (5.40 t ha-1), straw yield (6.80 t ha-1) and biological yield (12.20 t ha-1) were obtained from BRRI dhan81 (V3) with hand weeding (H2) and highest harvest index (45.60%) were obtained from BAU dhan3 (V1) with Pretilachlor (H4). Therefore, this result is useful for farmers at field level cultivation of boro rice.