57 Indian Journal of Agricultural Sciences 80 (9): 815–9, September 2010 Efficacy of herbicides under different methods of direct-seeded rice (Oryza sativa) establishments MANDHATA SINGH 1 and R P SINGH 2 Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh 221 005 Received: 19 August 2009; Revised accepted: 1 June 2010 ABSTRACT A field experiment was conducted during rainy (kharif) season of 2006 and 2007 to study the efficacy of herbicides under different methods of direct-seeded rice (Oryza sativa L.) establishment. Establishment of rice by drum seeding significantly reduced the weed density and their dry weight and increased the yield-attributing characters finally led to 0.28 and 0.64 tonnes/ha higher rice yield over the wet (4.27 tonnes/ha) and dry seeding (3.91 tonnes/ha) of rice. Application of pretilachlor fb 2,4–D (0.75 fb 0.5 kg/ha) was most effective in lowering the weed density of grassy and non-grassy weeds and their dry weight, and thus enhancing yield attributes and yield (4.73 tonnes/ha) of rice. Weed control efficiency (84.23%) was maximum under this treatment compared with the other sequential application of herbicides, ie butachlor (71.90%) and pendimethalin (73.85%), followed by 2,4–D as well as their alone applications. Key words: Direct-seeded rice, Herbicides, Rice, Weeds Rice (Oryza sativa L.) is grown in different ecosystems and physical conditions of soil. Cultivation of rice by transplanting in rice–wheat (Triticum aestivum L. emend. Fiori & Paol.) cropping system is most popular in north India but it is highly labour-intensive and expensive method of cultivation, as well as it requires large quantity of water for puddling, transplanting and establishment of rice seedlings. Most of the farmers are marginal, unable to bear the cost in carrying out these operations. In addition, long turn-around time and unpredictable monsoon rain delays the sowing of succeeding crop (Maity and Mukherjee 2008). Direct seeding either in puddled or in non-puddled conditions eliminates the need of raising, maintaining and subsequent transplanting of seedlings, which is labour-intensive. Besides, it is cost- effective can save water through earlier rice crop establishment and allows early sowing of wheat (Singh et al. 2007). However, the crop is subjected to greater weed competition for various growth resources, viz nutrients, light and space than transplanted rice because both crop and weed seeds emerge at the same time and its yield is reduced up to 50–100% (Rao et al. 2007). Uncontrolled weeds reduce the yield by 96% in dry direct-seeded rice, 61% in wet direct- seeded rice and 40% in transplanted rice (Kim and Pyon 1998). Therefore, control of weeds is important to reduce the weed competition as well as to maximize the efficient utilization of resources to raise the productivity of the crop. Herbicides are considered to be an economical alternative to manage weeds against age-old practice of hand weeding, which is costlier and also becomes impracticable due to non- availability of labourers during critical period of weeding. Herbicides are used to manage either grassy or non-grassy weeds in rice, and none of the herbicide is available to manage both the types of weeds. Further, weeds emerge in direct- seeded rice in different flushes, and pre-emergence application of herbicides fails to manage later emerging weeds after 3 weeks due to short persistence. Therefore, the present study was undertaken to evaluate the comparative performance of different methods of rice establishment and to evaluate efficacy of herbicides alone and in combination in different methods of direct-seeded rice establishment on weed density, weed dry weight, weed control efficiency and yield of rice. MATERIALS AND METHODS A field experiment was conducted during rainy (kharif) seasons of 2006 and 2007 at the research farm of the University, Varanasi. The soil was Gangetic alluvial having sandy loam in texture with pH 7.4. It was moderately fertile, being low in available organic carbon (0.43%), available N (197.02 kg/ha), and medium in available P (23.41 kg/ha) and K (210 kg/ha). The experiment was laid out in split-plot design with 3 sowing methods, viz wet seeding (broadcasting of sprouted seeds under puddled condition), dry seeding in 1 Research Scholar (email_ mandhataa@gmail.com), 2 Professor (email: rpsingh.bhu@yahoo.com), Department of Agronomy