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for the tropics. The hybrids have a yield
advantage of 15% to 20% over the currently
inbred high-yielding varieties. Rice hybrids were
developed in China. The increase in rice yields in
China during 1975-90 was due largely to the
diffusion of hybrid varieties to 50% of the rice
area. The Chinese hybrids are not suitable for the
tropical climates in Southeast and South Asia.
IRRI scientists have developed suitable hybrid
lines for the tropics and these are now being used
by scientists in India and Vietnam to develop
varieties for release to farmers. However, with
the high cost of seeds and low prices (because of
inferior grain quality), hybrid rice varieties do
not have an advantage over the high-yielding
varieties with regard to profitability. This will
constrain the adoption of hybrid rice by farmers
unless breeders are successful in developing better
quality hybrids with higher heterosis. Another
constraint may be that, when using hybrids,
farmers need to change seeds every season,
which is an unconventional practice.
Yields in the rainfed ecosystem have increased
only marginally, from 1.4 to 2.1 t/ha over
the last few decades. There is a vast potential for
increasing production from the rainfed system by
reducing the large yield gap. But rice scientists
have yet to succeed in developing appropriate
high-yielding varieties that can withstand prolonged
drought, temporary submergence, and
other climatic stresses common in the fragile
rainfed environments. The probability of success
in making scientific breakthroughs in this area is
low.
Growing scarcity of land and water
Natural resource constraints to increasing rice
production are becoming severe for most of the
low-income countries in Asia. The per capita
availability of arable land has been declining
rapidly with growing populations. China now
supports 17 persons per hectare of arable land,
Bangladesh 13, Vietnam 11, and India, Indonesia,
and the Philippines 8 to 10. Only Thailand,
Myanmar, and Cambodia have favorable endowments
of land, with 2 to 4 persons per hectare.
The area under rice cultivation is expected
to decline with economic prosperity and
urbanization as the demand for land for
nonagricultural uses increases. There will also be
economic pressure to release rice land in favor of
vegetables, fruits, and fodder, whose markets
become stronger with economic progress.
The scope for further irrigation of rainfed
lands is limited because of the increasing cost of
irrigation and environmental concerns regarding
its adverse effects on waterlogging, salinity, fish
production, and the quality of groundwater.
Water is also becoming a scarce commodity.
In absolute terms, annual water withdrawals are
by far the greatest in Asia, where agriculture
accounts for 86% of total annual withdrawal
compared with 38% in Europe and 49% in North
and Central America. The per capita availability
of water resources declined by 40% to 60% in
most Asian countries during 1955-90 and is
expected to decline further.
Sustaining interest in rice farming
Even if all the physical and environmental
constraints to production are overcome, many
countries of South and Southeast Asia will still
face the problem of sustaining farmers’ interest
in rice cultivation. The expansion of industry and
the services sector in urban areas, increasing
nonfarm activities in rural areas, and rapidly
rising labor productivity are contributing to a
long-term upward trend in wage rates. In Japan,
Taiwan (China), and the Republic of Korea,
rural-urban migration of the agricultural labor
force has caused a continuous decline in the
farming population, making it difficult to sustain
rural communities in some areas.
The increasing cost of rice production in
middle- and high-income countries is preventing
them from exporting surplus rice that has
resulted from declining domestic consumption.
Instead, it has lowered production. In Japan, the
rice harvest reached 18.8 million t in 1967, after
which it gradually fell to 10 million t in 1999. In
Taiwan (China), the harvest reached 3.6 million t
in 1976, whereas current production is below 2.0
million t. Meanwhile, growing scarcity of land,
labor, and water continues to drive up the cost of
rice production in spite of more efficient use of
inputs (through improved crop management
practices) and saving of labor (through mechanization).
The unit cost of production is 10 times
higher in Japan and seven times higher in the
Republic of Korea than in Thailand and Vietnam,
the major rice exporters in the world market
(Table 4). The Japanese government has encouraged
farmers to divert rice land to other crops,
but not all rice land is suitable for other crops.
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