INFLUENCE OF WEED CONTROL METHODS ON THE GROWTH AND YIELD OF AROMATIC AMAN RICE VARIETIES

Abstract

A field experiment was conducted in medium fertile soil at Sher-e-Bangla Agricultural University (90º33´ E longitude and 23º77´ N latitude), Dhaka, Bangladesh during July to December, 2011 in aman season with a view to find out the performance of transplant aromatic rice varieties under different weed control methods. The experiment was carried out with four varieties i.e. BRRI dhan34, BRRI dhan37, BRRI dhan50 and Chinigura in the main plot and five weed management methods viz. control (no weeding), one hand weeding at 15 DAT, two hand weeding 15 DAT + 40 DAT, Topstar 400SC (Oxadiargyl 400 g L -1 ) @ 100 g ha -1 as post-emergence and Sunrice 150WG (Ethoxysulfuron 150 g kg -1 ) @ 185 ml ha -1 as pre-emergence herbicide in the sub plot in split plot design. Twenty three different weed species infested the field among which Echinochloa crussgalli (51.79%) at 15 DAT, Cyperus michelianus (56.14%) at 30 DAT, Cyperus esculentus (24.93%) and Cyperus difformis (24.54%) at 45 DAT, Cyperus esculentus (33.6%) at 60 DAT and Ludwigia octovalvis (21.88%) at 75 DAT were dominant. BRRI dhan34 gave highest (3.16 t ha ) and BRRI dhan50 produced lowest grain yield (1.88 t ha -1 ). The result showed that pre-emergence herbicide Sunrice 150WG controlled weeds very significantly which showed highest growth and yield contributing characters of rice. Application of Sunrice 150WG showed highest weed control efficiency at 30 DAT 95.28% and 78.95% at 60 DAT. The grain yield produced by Sunrice 150WG was 50.73%, 32.07%, 11.95% and 5.25% higher than the yield obtained from control, one hand weeding, two hand weeding and Topstar 400SC treated plots, respectively. Considering weed control cost, Sunrice 150WG was found more economic for controlling weeds in transplant aromatic aman rice and benefit cost ratio was 2.26 whereas, 1.17, 1.30, 1.46 and 2.14 were found from control, one hand weeding at 15 DAT, two hand weeding at 15 DAT + 40 DAT and Topstar 400SC, respectively. The interaction showed that BRRI dhan34 in combination with Sunrice 150WG produced the highest grain yield (4.10 t ha ) while lowest grain yield (1.44 t ha -1 ) was obtained from BRRI dhan50 in control treatment. -1 -1