Book of Extended summaries ISDA

International Conference on Reimagining Rainfed Agro-ecosystems: Challenges & Opportunities
during 22-24, December 2022 at ICAR-CRIDA, Hyderabad
T4a-52P- 1137
Weedy rice: A Threat to Sustainable Rice Production under Direct Seeding
V. Anjaly
Ph.D. scholar, Department of Agronomy, Punjab Agricultural University
Rice is the staple food of more than 50% of the world’s population and the conventional method
of rice growing, which involves puddling followed by transplanting, is a labour and water
intensive process. Increased costs or decreased availability of irrigation water and labour has
forced the farmers in Asia to slowly proceed towards direct seeding of rice (Chauhan, 2012). The
absence of suppressive effect of standing water on weed emergence and similarity in seed sizes
of crop and weeds has led to the serious concern of weedy rice infestation in most of the rice
growing tracts. Weedy rice infestation raises the production costs, lowers the crop yield and
qualitatively decreases the farmer’s income, through reduced seed value at the time of harvest .
In recent years, weedy rice has emerged to be one of the major troublesome weeds in rice
growing Asian countries, including Malaysia, Thailand, Philippines, India, Republic of Korea,
Vietnam and Sri Lanka
Weedy rice (Oryza sativa f. spontanea) is believed to be evolved through the interbreeding
between cultivated rice (O. sativa) and wild rice (O. nivara/O. perennis) (Chauhan, 2013). The
physical and physiological similarities of weedy rice to cultivated rice have made the weedy seed
spread more easier through crop seed contamination. Features like faster growth, profuse tiller
production, early flowering and high competence for nutrients, light and space provide them
competitive advantage over cultivated rice. The weed is also characterized by longer seed
dormancy, easy seed shattering (enhance weed seed bank), presence of awns, red pericarp and
pigmented aleuronic layer, and the ability to thrive in adverse agro-climatic conditions
Weed management strategies such as use of clean rice seeds and machineries, regular inspection
and roguing of weedy rice plants before seed set, repeated cultivation of rice fields, stale seed
bed technique, use of transplanting technique wherever plenty of exploitable water is available,
use of high seeding rates, row seeding using seed drills, and use of weed competitive crop
cultivar with early vigour and quick canopy closure, are advocated (Chauhan, 2013). An
improved broadcasting method called ‘parachute planting’ is practiced in Vietnam and Sri
Lanka, in which the rice seedlings, grown in nursery, are thrown onto the puddled soil, with
water depth maintained at 5 to 10 cm. Chauhan et al. (2014) concluded that seedling broadcast
and transplanted rice methods are the most effective rice establishment techniques to reduce
weedy rice panicles and seed production, and to attain highest rice grain yield. Adoption of
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