Journal of Natural Disaster Science

COOL WEATHER DAMAGE IN RICE IN NIIGATA PREFECTURE, 1993

Hajime ARAKI, Toshiei SATO and Michiaki ITO
University Farm, Niigata University, Muramatsu, Niigata 959-17, Japan

(Received 1 December, 1995 and in revised form 10 April, 1996)

Abstract

Rice production in Japan suffered from severe type of cool weather; decreased temperature, decreased sunshine, and heavy rainfall, during the cropping season of 1993. Historical change in the main rice cultivars in Niigata Prefecture and their characteristic yields in cool weather therefore were investigated. Early maturing cultivars mainly were cultivated until ca.1975. Thereafter, the cultivation area of the middle maturing 'Koshihikari' gradually increased, being more than 60% of the total paddies in Niigata Prefecture in 1985 and, in the Uonuma area more than 85%. The 1993 yield of early maturing varieties was 85 to 93% of the normal yields due to the decrease in the ripened grain percentage. In contrast, the percentage of ripened grain and l,000 grain weight of 'Koshihikari', one of the most common cultivars, decreased 3 to 10% as compared with a normal year, resulting in ca. a 10% decrease in brown rice yield. The heading of 'Koshihikari' was delayed in paddies more than 400 m above sea level, and the yield decreased because of the reduction in the percentage of ripening. Thus, 'Koshihikari' appears to require careful cultivation techniques in order to avoid cool weather damage.

Key words

cool weather damage, rice cultivar, brown rice yield, cultivation area, sea level