119 2(3):119-134 (2013) Review article Management of direct seeded rice for enhanced resource - use efficiency Ekta Joshi 1 , Dinesh Kumar 1 , B. Lal 2*, V. Nepalia 3 , Priyanka Gautam 2 and A. K. Vyas 1 1 Division of Agronomy, Indian Agricultural Research Institute, New Delhi, India-12 2 Crop Production Division, Central Rice Research Institute, Cuttack, Odisha, India-753006 3 Department of Agronomy, Rajasthan College of Agriculture, Udaipur-313001, India *Corresponding author: blaliari9404@gmail.com Abstract Rice (Oryza sativa), the staple food of more than half of the population of the world, is an important target to provide food security and livelihoods for millions. Imminent water crisis, water-demanding nature of traditionally cultivated rice and climbing labour costs ramble the search for alternative management methods to increase water productivity, system sustainability and profitability. Direct seeded rice (DSR) technique is becoming popular nowadays because of its low-input demanding nature. It offers a very exciting opportunity to improve water and environmental sustainability. It involves sowing pre-germinated seeds into a puddled soil surface (wet seeding), standing water (water seeding) or dry seeding into a prepared seedbed (dry seeding). The development of short duration, early-maturing cultivars and efficient nutrient management techniques along with increased adoption of integrated weed management methods have encouraged many farmers to switch from transplanted to DSR culture. This technology is highly mechanized in some developed nations like U.S, Europe and Australia. This shift should substantially reduce crop water requirements and emission of greenhouse gases. The reduced emission of these gases helps in climate change adaptation and mitigation, enhanced nutrient relations, organic matter turnovers, carbon sequestration and also provides the opportunity of crop intensification. However, weed and nematode infestation are major problems, which can cause large yield losses in DSR. Other associated problems with DSR are increased incidences of blast disease crop lodging impaired kernel quality, increased panicle sterility and stagnant yields across the years. Based on the existing evidence, the present paper reviews the integrated package of technologies for DSR, potential advantages and problems associated with DSR, and suggest likely future patterns of changes in rice cultivation. Keywords: Direct seeded rice, Greenhouse gas emission, Resource conservation, Seed priming, Water saving, Zero tillage, Weeds. Abbreviations: AWD_alternate wetting and drying; CE_Crop establishment; CEM_Crop establishment methods; CRF_controlled release fertilizers; CT_Conventional tillage; DAS_Days after seeding/sowing; DSR_Direct seeded rice; IGP_Indo-gangetic plains; MG_Meloidogyne graminicola;RKN_root-knot nematode; TPR_Transplanted puddled rice; ZT_zero tilled/ tillage. Introduction Direct seeding of rice refers to the process of establishing the crop from seeds sown in the field rather than by transplanting seedlings from the nursery (Farooq et al., 2011). Direct seeding avoids three basic operations, namely, puddling (a process where soil is compacted to reduce water seepage), transplanting and maintaining standing water. There are three principal methods of (Table 1) establishing the direct seeded rice (DSR): dry seeding (sowing dry seeds into dry soil), wet seeding (sowing pre-germinated seeds on wet puddle soils) and water seeding (seeds sown into standing water). Wet- DSR is primarily done under labour shortage situation, and is currently practiced in Malaysia, Thailand, Vietnam, Philippines, and Sri Lanka (Pandey and Velasco 2002; Weerakoon et al., 2011). But with the elevating shortages of water, the incentive to develop and adopt dry-DSR has increased. Dry-DSR production is negligible in irrigated areas but is practiced traditionally in most of the Asian countries in rainfed upland ecosystems. Water seeding is widely practiced in the United States, primarily to manage weeds such as weedy rice, which are normally difficult to control. Prior to the 1950s, direct seeding was most common, but was gradually replaced by puddled transplanting (Pandey and Velasco 2005; Rao et al., 2007). In Asia, rice is commonly grown by transplanting one month-old seedlings into puddled and continuously flooded soil (land preparation with wet tillage). The advantages of the traditional transplanted puddled rice (TPR) system of crop establishment include increased nutrient availability (e.g. iron, zinc, phosphorus), weed suppression (Surendra et al., 2001), easy seedling establishment, and creating anaerobic conditions to enhance nutrient availability (Sanchez 1973). The transplanted puddled rice (TPR), leads to higher losses of water through puddling, surface evaporation and percolation (Farooq et al., 2011). Repeated puddling adversely affects soil physical properties by dismantling soil aggregates, reducing permeability in subsurface layers, and forming hard- pans at shallow depths (Sharma et al., 2003), all of which can negatively affect the following non-rice upland crop in rotation (Tripathi et al., 2005a). Excessive pumping of water for puddling in peak summers in north west Indo-gangetic plains (IGP) causes problems of declining water table and poor quality water for irrigation on one hand, whereas, in Plant Knowledge Journal Southern Cross Publishing Group ISSN: 2200-5390 Australia EISSN: 2200-5404