HERBICIDES in Asian rice - IRRI books - International Rice ...

Table 4. Estimated area of direct-seeded rice in 1994 in selected Asian countries.
Country
China a
India b
Japan c
Thailand d
Vietnam e
Indonesia f
Philippines g
Malaysia h
Myanmar i
Area of direct-seeded rice (%)
Of 33 milllion ha of rice area sown in China, only about 5-10% are directseeded.
More than 50% of total rice area is transplanted by hand, the
remainder is transplanted by machine.
Approximately 70% of India's 42.1 million ha sown to rice are direct-seeded,
most of the remaining 30% is transplanted by hand.
Less than 0.5% of Japan's 2.14 million ha of rice are direct-seeded, the
remaining 99.5% area are machine transplanted.
Thirty-three percent of 8.8 million ha of rice are direct-seeded.
Direct-seeded rice covers about 94% of the total rice area in the Mekong
Delta, which accounts for 50% of rice production in Vietnam.
Direct seeding is practiced on 3.5% of total rice area (on and off Java) confined
to rainfed and upland ecosystems in the wet season. There is virtually no
direct-seeded rice in irrigated areas.
About 30% of irrigated rice area is direct-seeded in the dry season.
More than 80% of total rice area in Peninsular Malaysia and more than 60%
of rice area in the country as a whole is direct-seeded.
Almost 50% of total rice area is direct-seeded in the dry season.
Sources: a K. Li, pers. commun.. 1994, Asia-Pacific Regional Research and Training Center for Integrated Fish
Farming, Wuxi City, PRC: and H. Tang, Institute for Plant Protection, Shanghai, PRC. b V.M. Bhan, pers. commun..
1994, National Research Center for Weed Science, Jabalpur, India; and D.N. Sen, Department of Botany,
University of Jodhpur, India. c H. Shibayama. pers. commun.. 1994, Marine and Highland Bioscience Center,
Saga University, Japan. d P. Vongsaroj, pers. commun., 1994, Botany and Weed Science Division, Department of
Agriculture. Bangkok, Thailand; Vongsaroj (1994); Sittisuang (1994). e D.V. Chin, pers. commun., 1994, Cuu
Long Delta Rice Research Institute; Chuong and Yamauchi (1994). f C.P. Mamaril, pers. commun.. 1994, IRRI,
Bogor. Indonesia. g Garcia et al (1994), Pandey (1994). h Supaad and Cheong (1994). Jaafar et al (1994). i Tin
and Hia Min (1994), Yamauchl et al (1994).
Philippines, and Vietnam (De Datta 1989, De Datta and Nantasomsaron 1991). The
data suggest that direct seeding is not suitable for all rice-growing regions. Direct
seeding requires effective weed control as well as efficient water control and level
fields for adequate seed germination.
Herbicides are now used extensively in Asian rice production systems primarily
because they are profitable to farmers. Experiments on weed control practices for
both transplanted and direct-seeded flooded rice indicate that the benefit-cost ratios
to farmers are most favorable when herbicides are used (Ampong-Nyarko and De
Datta 1991, De Datta 1989). The benefit-cost ratio measures net returns to rice production
with different weed control practices in relation to returns without weed control
(Naylor 1994a). The research shows that the benefit-cost ratio of controlling weeds
with herbicides in transplanted rice is 16:1; the benefit-cost ratio for hand weeding is
Herbicide use in Asian rice production 7