Effects of Seeding Time and Weed Control Methods in Direct Seeded Rice (oryza Sativa L.)

Field experiments were conducted during the 2 year period from 2008 and 2009 to determine the effects of three seeding dates and seven weed control methods in DSR. The results suggested that seeding in the first week of July reduced weed density and biomass, increased kernel weight, leaf area index, and kernel yield compared to seeding rice in the first week of July. Amongst weed control methods, penoxsulam followed by hand-hoeing at 30 days after seeding (DAS) reduced weed density as low as ≤ 6 and ≤ 28 plants m at 35 DAS and at harvest, respectively during both the years which was comparable with hand-hoeing at 15, 30 and 45 DAS. In addition, rice yield attributes including number of tillers, kernel weight, leaf area index, leaf area duration were higher, while kernel yield in this treatment was 70 and 61% higher compared to nontreated control during 2008 and 2009, respectively. A foliar spray of sorghum and sunflower water extract at 20 and 40 DAS and sorghum mulch at 6 t ha were effective for weed control and secured kernel yield respectively, > 33% and 27% higher compared with the non-treated control. However, they were not as effective as penoxsulam, bispyribac-sodium, and/ or hand-hoeing treatments. The interaction effect of seeding time and weed control methods was significant for most of the variables. It is concluded that penoxsulam would be an additional chemical tool if integrated with hand-hoeing for weed control in DSR. Nomenclature: Bispyribac-sodium; penoxsulam; Rice, Oryza sativa L.; sorghum, Sorghum bicolor (L) Moench.; sunflower, Helianthus annus L.