Abstract: The establishment of process rainfall indices for waterlogging damage to rice in cold region is important for coping with climate change, preventing and mitigating natural disasters, and ensuring production safety. Based on historical data of waterlogging damage and phenophase of japonica rice from 1961 to 2000, combined with daily precipitation data of 73 meteorological stations, we inverted rainy days and process rainfall of waterlogging at the key growth period of rice and established the process precipitation sequence of cold rice waterlogging samples, with japonica rice in Heilongjiang Province as the research object. The precipitation level index of waterlogging process of rice in cold regions was constructed by using K-S distribution fitting test and the lower limit value of confidence interval to determine the threshold value. The indices were verified with the reserved disaster samples. The results showed that under the condition of poor drainage of cropland, when rainy days were within 1-3, the lower limits of rainfall for rice with mild, moderate and severe waterlogging were 48, 89 and 136 mm at tillering stage, and 44, 87, 102 mm at heading stage, respectively. When rainy days were within 4-7, the lower limit values of rainfall were 68, 97 and 142 mm at tillering stage, and 66, 103, 127 mm at heading stage, respectively. The calculated results of the indices were well consistent with the historical waterlogging damage records. Our results can provide support for quantification of rice waterlogging damage in cold regions.

Key words: melon root exudates, phenolic compounds,  allelopathic effects,  Fusarium oxysporum f. sp. melonis, Fusarium wilt.