Seeding rate and herbicides suppress weeds and affect the relative performance of rice (Oryza sativa) varieties in dry direct-sown conditions in eastern India

A field experiment was carried out during dry seasons of 2014 and 2015 at Cuttack, Odisha to investigate the effect of seeding rates and weed-control treatments on performance of rice varieties in dry direct-sown rice (Oryza sativa L.). Rice varieties CR Dhan 304 and Naveen were grown with 4 seeding rates, viz. 20, 30, 40, 50 kg/ha, and herbicide treatments, viz. single application of bispyribac-sodium and combined application of bispyribac-so- dium and azimsulfuron along with 2 controls (weed-free and weedy check). The experiment was laid in a split-split plot design. Significantly lower weed density (20 plants/m2) and dry weight (5.33 g/m2) were recorded under CR Dhan 304 than Naveen (21.06 plants/m2 and 5.61 g/m2). Seeding rate of 50 kg/ha resulted in the highest weed suppression in terms of weed density (4.63 plants/m2) and dry weight (2.82 g/m2). Among the herbicide treat- ments, the maximum grain yield was recorded with combined application of herbicides (5.8 t/ha), which was at par with weed-free treatment (5.9 t/ha) and significantly higher than the single application of bispyribac-sodium (5.4 t/ ha). CR Dhan 304 and Naveen varieties recorded net benefit: cost (B:C) ratio of 1.25 and 0.75 respectively. Among the weed-management practices, combined application of herbicides recorded the highest B : C ratio (1.52). Based on our findings, rice variety CR Dhan 304 suppressed weeds, and high seeding rate (50 kg/ha) combined with application of herbicides (bispyribac-sodium and azimsulfuron) may be recommended in dry direct- sown rice in coastal plain areas of eastern India.