Weed Management Improves Yield and Quality of Direct Seeded Rice (Report‪)‬

Introduction Rice is the staple food for billions of people worldwide. Rice is the second most important cereal crop of Pakistan grown on an area of 2.96 m [ha.sup.-1] with total production of 6.95 m tons and average yield of 2.3 t [ha.sup.1] (Govt. of Pakistan, 2008-09). Fine grain rice named as 'Basmati' is an important brand of Pakistan fetching special price in the international market and has a major share in the rice export earnings of Pakistan. Total export value of rice in Pakistan is 1150.1 million US $ (Govt. of Pakistan, 2008-09). Pakistan exports quality rice to countries of West Africa, Malaysia, Bangladesh, Iran, Indonesia, United Arab Emirates and Saudi Arabia. Conventional method of rice growing in Pakistan is the raising of rice nursery in a nursery bed and transplanting one month old nursery seedlings in a puddled and flooded field (Ehsanullah et al. 2007). This method not only effectively suppresses the rice weeds by preventing the light to reach the weeds through a layer of the standing water and also provides the rice plants with a better growing environment (Rao et al. 2007; Begum et al. 2006; Chauhan and Johnson, 2009; Farooq et al. 2011). However, immense labor and water is required to grow rice by conventional flooded method (Bouman et al. 2007; Bhushan et al. 2007). In the backdrop of the declining water resources and reduced availability of the labor, the conventionally flooded rice system is losing its sustainability and economic viability (Guerra et al. 1998; Bhushan et al. 2007). Declined water table, increasing costs of diesel and electricity and climatic changes have further aggravated the problem (Vorosmarty et al. 2000; Rosegrant et al. 2002). Due to these reasons there is a need to shift from the conventionally flooded transplantation to direct seeding of rice in Pakistan. Direct seeding of rice is an alternative option to cope with the problems of water and labor scarcity associated with conventionally flooded rice (Weerakoon et al. 2011). Direct seeding of rice is accomplished by either of the methods as water seeding, wet seeding and dry seeding (Ehsanullah et al. 2007; Bouman et al. 2007; Farooq et al. 2011). Direct seeded rice is being cultivated successfully in many parts of the world like China, Australia, Malaysia, United States, and Sri Lanka etc. (Tabbal et al. 2002; Farooq et al. 2011; Weerakoon et al. 2011). Weeds are the serious constraint to the productivity of direct seeded rice (Caton et al. 1999; Zhao et al. 2006; Singh et al. 2006; Rao et al. 2007; Sanusan et al. 2010). There is abundance of weeds of diverse nature in fields under direct seeded rice (Sharma et al. 1977; Chin, 2001; Tomita et al. 2003; Singh et al. 2008a; Kamoshita et al. 2010). Weeds grow quickly in direct seeded rice compared with the weeds growth in transplanted flooded rice and other crops (Karim et al. 2004; Begum et al. 2006; Chauhan and Johnson, 2009; Kamoshita et al. 2010). These weeds severely disturb the growth of rice and sometimes result in the failure of the crop (Phuong et al. 2005). Different weed control practices have been evaluated to minimize the weed pressure in direct seeded rice (Phuong et al. 2005; Chauhan et al. 2010). Application of weedicides effectively suppress the weeds and provide the direct seeded rice a weed competition free environment (Gitsopoulo and Froud-Williams, 2004). Pendimethalin, butachlor, oxadiazon and nitrofen are among the herbicides which have been tested worldwide for controlling weeds and improving the yield of direct seeded rice (Rao et al. 2007; Farooq et al. 2011). Mechanical weed control and hoeing may also suppress the weeds and increase grain yield in direct seeded rice (Rao et al. 2007). As weeds are the main hindrance in the direct seeded rice in Pakistan so an urgent solution is needed to suppress weeds and enhance yield of direct seeded rice. This study was planned to determine the effectiveness of different weed control measures to enhance the yield