FOOD SECURITY - Science for Agriculture and Rural Development in Low-income Countries - page 43

production decline, as was observed in 2004. Increasing competition for water
between industrial and domestic use and rice cropping in China may be an
additional reason to replace wetland rice by dryland crops.

Rice yields
Rice yields in all countries in Asia were about 2000 kg/ha in the period around 1960.
From then on, yields rapidly increased as a result of adoption of improved rice
varieties (hybrids, short-straw varieties) and improved crop management (i.e., increased
fertilizer nutrient supply, improved irrigation management, crop protection, soil tillage,
and later also more mechanized farm operations). The yield increase started earliest
(around 1960) in China, leading to a tripling in 30 years to about 6000 kg ha -1 in the
1990s and then to stabilization (Figure 5). In Indonesia, yields increased rapidly
from about 1975 to about 2.5 times the 1960 level in the 1990s. Yield increase in
India and in particular in Thailand (only 55% higher than in 1961) was more limited
due to less favourable growing conditions (large areas with poor soils and with uncer-
tain water supply and rainfall). In Vietnam, yield increase started later (second half
of the 1980s), and recently, yields attained values exceeding 4500 kg ha -1 . It already
surpasses mean yields in all other countries in Asia, except for China (Figure 5).

While increases in rice production and yields in the last 50 years have been

spectacular, there are major constraints to further increasing food supply in Asia.
One of these constraints is presented by stagnating cereal yields on intensively used
agricultural lands. Others include strong competition between agriculture and other
sectors for scarce land and water resources, and possible yield reductions as a
consequence of climatic change. Associated research challenges are presented at the
end of this chapter.

Yield (kg/ha)

8000

China
India
Indonesia
Thailand
Viet Nam

6000

4000

2000

0

1960 1970 1980 1990 2000 2010

Yea r

Figure 5. Development of rice yields in selected Asian countries: 1961-2004