Evaluation of Herbicides Efficacy to Control the Complex Weed Flora of Dry Direct Seeded Rice (Oryza sativa L.)

Abstract

First thing which strike in researcher’s mind whenever they talk about dry direct seeded rice (DSR) is weed, no doubt Dry DSR is a promising resource conservation technology (RCT) but its acceptance among rice growers is obstructed due to heavy weed conquest. A field study was conducted at GBPUAT, Pantnagar to evaluate the efficacy of herbicides to control the complex weed flora of Dry DSR (Oryza sativa L.). Total ten herbicides were evaluated in the experiment which were consisted application of Pyrazosulfuron 25, Pretilachlor 750, Chyhalofop butyl 90, Fenoxaprop 60, Cyhalofop butyl +(chlorimuron + metsulfuron) 90+20, Fenoxaprop +(chlorimuron + metsulfuron) 60+20, Azimsulfuron 35, Bispyribac sodium 25, Fenoxaprop +Ethoxysulfuron 60+15 and Oxyflurofen + 2,4-D 300+500 g ha-1 respectively. Grassy weeds dominant the field throughout the growing season. Up to 60 days after sowing (DAS) sedge share 25-30% in total weed population in weedy plot, but later on grassy weeds surpass and maintain above 85% of total weed share up to harvest. Among different herbicides Fenoxaprop +Ethoxysulfuron 60+15 recorded highest weed control efficiency (91.9%) followed by Fenoxaprop +(chlorimuron + metsulfuron) 60+20 (85.6%) and Bispyribac sodium 25 g ha-1 (85.4%) at 60 DAS. Pre-emergence herbicides like Pyrazosulfuron 25, Pretilachlor 750 and Oxyflurofen + 2,4-D 300+500 g ha-1 were not found effective to control weeds and face heavy weed infestation from very early stage of crop. Post-emergence herbicides like as Fenoxaprop +(chlorimuron + metsulfuron) 60+20 recorded the highest grain yield (34.01 q ha-1) followed by Fenoxaprop +Ethoxysulfuron 60+15 (31.78 q ha-1) and Bispyribac sodium 25 g ha-1 (31.75 q ha-1) which were at par with two hand weeding (32.63 q ha-1) and Pyrazosulfuron at 25 (4.42 q ha-1) Pretilachlor 750 g ha-1 (4.38 q ha-1) gave non-significant yield increase over the weedy (4.16 q ha-1) plot.