Growth and Development of Upland Rice at Three Altitudes in the Highlands of Northern Thailand

Abstract

SUMMARYA number of upland rice varieties were grown in the highlands of northern Thailand at altitudes of 800, 1200, and 1450 m in 1978 and 1979. Growth rate declined and growth duration was extended as altitude increased. At the 1200 and 1450 m sites yield was severely restricted by spikelet sterility, probably induced by cool temperatures. Some varieties were completely sterile at the highest altitude, where yields ranged up to 2.6 t ha−1. At 800 m several varieties yielded more than 5 t ha−1 in 1978, but yields at this lower site were reduced by about 20% in 1979. Translocation to the grain of assimilates stored in the vegetative parts appeared to have been restricted. Lodging was a problem at all sites.