Impact of reduced rate of pre-emergence herbicide with aqueous extract of mustard crop residues on different weed management indices and yield of transplanted aman rice

Effective weed management with herbicides and crop extracts boosts rice yield and growth. In this respect, a field experiment was conducted from July to December 2023 at the Agronomy Field Laboratory (AFL), Bangladesh Agricultural University (BAU), Mymensingh, to evaluate the effect of mustard crop residue extract combined with reduced herbicide doses on the yield and attributes of T. aman rice. The study involved three rice varieties BRRIdhan49, BRRI dhan87, and Binadhan-7 and seven treatments: no weeding (control), recommended dose of herbicide at pre-emergence (RDHP), mustard crop extract (MCE), 80% RDHP + MCE, 70% RDHP + MCE, 60% RDHP + MCE, and weed-free conditions. Results showed the highest weed growth in control treatment and the lowest in the weed-free treatment, with 80% RDHP + MCE showing the second-lowest weed growth. The weed-free treatment achieved the highest weed control index (WCI), weed control efficiency (WCE), and herbicide efficiency index (HEI), while minimizing weed index (WI), weed population index (WPI), weed mass index (WMI), and the Ammonia Index (AMI), followed by 80% RDHP + MCE. BRRI dhan87 produced the highest grain yield (5.36 t ha-¹), while BRRI dhan49 had the lowest (4.54 t ha-¹). The highest yield was recorded in the weed-free treatment (5.80 t ha-¹), followed by 80% RDHP + MCE (5.35 t ha-¹), and the control produced the lowest yield (2.63 t ha-¹). The study concludes that using 80% RDHP combined with MCE is an effective weed control strategy that enhances T. aman rice yield by reducing herbicide dependency.