Abstract

Weeds, crop residues, bispyribac sodium, penoxsulam, weed suppression, grain yield.

Dry seeding of rice offers potential to be opted as a resource conservation technology but its sustainability is endangered by heavy weed infestation. Experiments were conducted during summer season of 2009 to look for effective and economically viable weed control method(s) in dry seeded rice. Four mulching materials of natural origin as sorghum, sunflower and wheat residues each soil incorporated at 8 t ha-1 and black polyethylene sheet strips as artificial origins were used. A weedy check and manual weeding were included for comparison. Label doses of post emergence herbicides, bis-pyribac sodium and penoxsulam, at 30 and 15 g a.i. ha-1 were also used. Manual weeding accounted for maximum (99%) inhibition in weed density and dry weight. Bispyribac sodium suppressed weed count and dry weight by ≈ 80%. Among non-chemical weed management strategies, sorghum residues scored over 50% reduction in weed density and dry weight. Plastic sheet strips were least effective against weeds. Manual weeding scored highest paddy yield of 4.17 t ha-1 . Bispyribac sodium with 3.51 t ha-1 paddy yield appeared superior to penoxsulam. Sorghum, sunflower and wheat residues resulted in statistically similar paddy yields of 2.85, 2.80 and 2.58 t ha-1 , respectively. Bispyribac sodium exhibited maximum marginal rate of return of 23076%. Chemical control proved to be a viable strategy with higher economic returns.