~ 742 ~ Journal of Pharmacognosy and Phytochemistry 2021; 10(2): 742-748 E-ISSN: 2278-4136 P-ISSN: 2349-8234 www.phytojournal.com JPP 2021; 10(2): 742-748 Received: 19-12-2020 Accepted: 08-02-2021 Jimni Phukan Department of Agronomy, College of Agriculture, Assam Agricultural University, Jorhat, Assam, India Sontara Kalita Department of Agronomy, College of Agriculture, Assam Agricultural University, Jorhat, Assam, India Priyanki Bora Department of Agronomy, College of Agriculture, Assam Agricultural University, Jorhat, Assam, India Corresponding Author: Jimni Phukan Department of Agronomy, College of Agriculture, Assam Agricultural University, Jorhat, Assam, India Weed management in direct seeded rice: A review Jimni Phukan, Sontara Kalita and Priyanki Bora Abstract Rice (Oryza sativa L.) is one of the staple food crops for more than half of global population and is mostly grown as transplanted crop. Recently, there has been a shift from transplanting to direct-seeding due to scarcity of water and labour. The transition towards direct seeded rice saves water, reduces duration to maturity as well as labour required. But weeds pose a serious threat in direct seeded rice compared to transplanting due to alternate wetting and drying. Thus, the success of direct seeded rice depends on effective weed management. Though manual weeding is the best but due to higher labour requirement, there is a need to use herbicide but the use of herbicides alone does not provide effective and sustainable weed control. Therefore, there is a need to integrate herbicide with alternate weed management approaches or pre-emergence herbicide followed by a post-emergence herbicide for effective weed management in direct seeded rice. In this review, we examine the extent of weed infestation, losses in direct seeded rice and earlier work on different weed management approaches in direct seeded rice. Keywords: Direct seeded rice, herbicide, hand weeding, integrated weed management Introduction Rice (Oryza sativa L.) is one of the leading cereals of the world and two-third of the Asian people receives their daily calories from rice (Rahman and Masood, 2012) [53] . Asia accounted for 60% of the global population, about 92% of the world’s rice production and 90% of gl obal rice consumption (FAO, 2012) [18] . Rice provides 30–75% of the total calories to more than 3 billion Asians (Khush, 2004) [32] . Rice is mostly grown by manual transplanting of seedlings into puddled soil which creates a hard pan below the plough layer and reduces soil permeability and deteriorates soil structure and soil quality for the subsequent upland crops. Puddling and transplanting operations consume a significant quantity of water; in some cases, up to 30 per cent of the total rice water requirement (Chauhan, 2012) [11] . This triggers the farmers to shift from manual transplanting to direct seeded rice systems. The advantages offered by direct seeded rice are early maturity, easy mechanization, less labour and water requirement. But, weeds are the number one biological constraint and major threat to the production and adoption of direct seeded rice systems and can cause rice yield losses of up to 50 to 91 per cent (Rao et al., 2007) [57] . In direct seeded rice, weeds could be managed by hand weeding (manual means). However, chemical weed management is replacing manual weeding due to meagre labour availability, escalating labour costs and drudgery involved. Sole use of herbicides may lead to the development of resistance in weeds, changes in the weed density and composition. Moreover, a single weed control approach may be unable to keep weeds below the economic threshold level. Therefore, adoption of integrated approach is essential for weed management in direct seeded rice to get targeted yield. Weed flora associated with direct seeded rice The extent of damage on crop growth and yield caused by weeds depend on weed species and their densities occurring in a crop community. The type of weed species and their persistence in a locality are highly influenced by crop, season, method of cultivation, date of sowing, climate, edaphic and biotic factors which limit their occurrence, density, range and distribution. Studies on the weed species and their densities competing with rice are more relevant to develop efficient weed control measures. Direct seeding results in change in the relative abundance of weed species. In particular, Echinochloa spp., Ishaemum rugosum, Fimbristylis miliacea and Cyperus difformis were widely adapted to the conditions of direct seeded rice (Rao et al., 2007) [57] . The major weed floras associated with direct seeded rice were Echinochloa colona, Echinochloa crussgali, Digitaria sanguinalis, Cyperus iria, Eleusine indica and Eclipta alba etc. (Mahajan and Timsina, 2011) [39] .