Dynamics of Rainfed Lowland Rice Varieties in Northeast Thailand
MIYAGAWA Shuichi
Faculty of Agriculture, Gifu University, Gifu 501-1193, Japan,
Email: miya@cc.gifu-u.ac.jp
ABSTRACT
Many kinds of rice varieties with a wide range of maturities were planted according to various
topo-sequences of rainfed paddy fields in Northeast Thailand until the 1980s. Ecological
meaning of various maturities was adaptation to different availability of water resource among
paddy fields. These varieties have been replaced by two medium-maturity varieties, RD6 and
Khao Dok Mali, since the beginning of the 1990s. This change is partly because of better eating
quality and higher economic value of these varieties. The present study will discuss this change
from the ecological and economic viewpoints.