Abstract
Cool weather is a serious climatic constraint for rice cultivation in hilly and mountainous regions. Deep-flood irrigation is known as the most effective method to protect rice plants from cool weather damage. Therefore, we examined its effects on the growth and yield characteristics of rice in hilly and mountainous regions. Three water management regimes were designed: DF-I (deep-flood irrigation from rooting stage to heading), DF-II(deep-flood irrigation from just before maximum tiller number stage to heading), and CWM (conventional water management). In 1999 and 2000, the maximum tiller number per m2 in the DF-I plot was smaller than those in the CWM plot. In contrast, the maximum tiller number per m2 in the DF-II plot was comparable to that in the CWM plot in both years. The panicle number per m2 in the DF-I plot was significantly lower than that in the DF-II plot in 1999 and the CWM plot in 2000. The rice yield in the DF-I plot was significantly lower than that in the CWM plot in 2000. However, the yield in the DF-II plot was the same as that in the CWM plot in both years. We conclude from these results that deep-flood irrigation from just before the maximum tiller number stage to heading is the most effective water management regime for avoiding cool weather damage and obtaining a stable rice yield in hilly and mountainous regions.
