Abstract
A field experiment was conducted at Ludhiana, during kharif 2008 to study effects of sowing time, variety and weed control on weed dynamics and productivity of dry/direct seeded rice. Six sowing dates (dry seeding on 0 (June 5), 7, 14, 21, 28 days after nursery sowing (DANS) and transplanting 28 DANS) in main plots and combinations of two varieties (PR 115 and PAU 201) and two weed control treatments (3 hand hoeings at 20, 40, 60 days and pendimethalin 0.75 kg pre-emergence followed by bispyribac-sodium 0.030 kg/ha as post emergence) in sub plots were evaluated in a split plot design with three replications. Transplanted crop recorded the lower population of all weeds sp and similar in dry seeding on 0 DANS. Population of all weed sp was lower under early sowing of crop on 0, 7 and 14 DANS as compared to delayed sowings. Population of Echinochloa sp, Leptochloa chinensis, Digitaria sanguinalis, Cyperus rotundus and Cyperus iria did not vary among seeding dates; Ammania baccifera and Caesulia axillaris intensity was significantly higher in 21 and 28 DANS as compared to early seeding dates. Weed density did not vary among rice varieties. Sequential application of herbicides effectively controlled Echinochloa sp and D sanguinalis while control of Eragrostis sp and L chinensis was very poor. Herbicides control broad leaf weeds and sedges except Cyperus rotundus. Transplanted crop recorded the highest rice grain yield and was at par to dry seeding 0 DANS but significantly higher than dry seeding on later dates. The grain yield of transplanted crop was 11.9, 22.1, 20.8, 41.7 and 71.4% higher as compared to dry seeding on 0, 7, 14, 21 and 28 DANS, respectively. Rice varieties recorded similar grain yield. Three hand hoeings gave significantly higher grain yield than herbicides. Rice seeding directly on 0, 7 and 14 DANS produced similar grain yield under herbicides and three hand hoeings; further delay in seeding significantly reduced grain yield under herbicides as compared to hand hoeings.
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