Abstract
Yield losses caused by low temperatures at the booting stage are a critical factor for producing rice in northern Japan. There is little information available on the spatial distribution of temperature at the booting stage that takes into account rice growth stages. The present study analyzed the spatial distribution of air temperatures not only at (1) the critical stage of the booting stage, but also at the two other stages that affect cold tolerance of (2) the early reproductive growth stage and (3) the late vegetative growth stage to produce a risk map for cold damage to rice in the Tohoku region of Japan. Regions that have lower temperatures at the booting stage are located to the north and east sides of Tohoku. Regression analysis using residual with temperature data at the booting stage and other two stages, respectively, highlighted the regions that carry a higher risk for suffering cold damage due to low temperatures at the booting stage; lower temperatures at the early reproductive growth stage and also at the late vegetative growth stage under temperatures identical to the booting stage. To reduce the risk for cold damage, manipulation of the cropping schedule is a powerful option. Delaying the heading date by one week can increase the critical temperature at the booting stage and also at the other two stages by up to 1°C.
