Paddy Field Characteristics in Water Use: Experience in Asia - Water and Agriculture: Sustainability, Markets and Policies - page 217

Australia. Maize is the dominant crop in South America, while wheat and maize account
for the majority of grain cultivation in North and Central America.
Paddy rice has a large physiological water requirement on the one hand, but is also
highly tolerant to inundation. Moreover, it has a higher ratio of production for food and a
lower ratio of use in international trade. Of the big three grain crops, therefore, rice could
be said to offer the greatest potential for human self-sufficiency. In contrast, maize has a
lower ratio of use for food, and is more important as a fodder grain (Table 3).

Table 2. Proportion of calories supplied by rice

Country/
region

Bangla-
desh

Cam-
bodia

Indo-
nesia

Korea
Rep.

Myan-
mar

Viet-
nam

Non-
Asia

Japan Laos Asia World

Pro-
portion of
calories
supplied
by rice (%)

72 75 50 23 31 66 71 66 31 3 20

Population
(mill.)

138 13 212 127 47 5 48 78 3,680 2,391 6,071

Source : IRRI's homepage, [Atlas of Rice & World Rice Statistics], www.irri,org/science/ricestat/index.asp FAO's homepage
[FAOSTAT], http://faostat.fao.org/faostat/collections?version=ext&hasbulk=0 .

Table 3. Comparison of world's three major grains

Water
required to
produce 1g
of dried
foodstuffs

Ability to
withstand
immersion

Consumption of
A as food

Amount of A
exported

Area under
cultivation
(2000)
(mill. ha)

Annual
production
(2000)
(A)
(mill. tons)

Name

B B/A C C/A

(%)
Rice paddy 154 600 682 High 521 87 36 6
Wheat 214 585 557 Low 419 73 138 24
Maize 138 593 349 Low 115 19 85 14
Notes: Rice production is based on unhulled rice. The amount of water required to produce 1g of dried foodstuffs has a degree of
latitude, depending on the reference.

(mill.
tons) (%)

(mill.
tons)

Source: Statistical Databases (UN Food and Agriculture Organization) / Black, C. C., T. M. Chen and R. H. Brown, Biochemical
basis for plant competition. Weed Soc. 17, 10-20, 1969.

Each year, the world uses about 3,572 km 3 of fresh water (or 641 cubic metres per
capita of population). About 60% of this total is used in Asia. Of the world's annual water
usage, about 70% or 2,504 km 3 is used by agriculture, and of this about 70% is used in
Asia alone. In Asia, the Middle East and North Africa, there are many countries in which
the use of water for agriculture has reached about 90% of all water extracted. Japan's
annual water use is about 88 km 3 or 691 cubic metres per capita of population, with about
two-thirds taken up by agriculture.