Abstract: The frequency of chilling injury during the soybean growing season in Heilongjiang province was higher, and the impact was severe. The index for delayed-type chilling injury on soybean in Heilongjiang province was calculated. It was important to prevent and mitigate disasters and ensure safe production of soybeans. In this paper, the soybean yield data of 73 cities and counties in Heilongjiang province from 1961 to 2020, and the daily temperature data of 73 weather stations in the research area were used. Anomalies value of the sum of monthly average temperatures from May to September were taken as hazard factors, respectively. The threshold was determined by regression, which used hazard factors and yield variability to calculate the threshold, which passed the test, and then established an index for delayed chilling injury on soybeans in Heilongjiang province. The results showed that, total monthly average temperature anomaly indicators for delayed chilling injury of soybeans in the study area from May to September correspond to five planting areas, the mild chilling injury thresholds were −1.8 ℃, −1.9℃, −1.9℃, −2.0℃, −2.0℃, moderate chilling injury thresholds were −2.0℃, −2.2℃, −2.3℃, −2.4℃, −2.6℃, and severe chilling injury thresholds were −2.2℃, −2.5℃, −2.7℃, −2.9℃, −3.1℃. After testing, the average accuracy rate of identifying the occurrence trend of delayed-type chilling injury in soybean was 83%, the average accuracy rate of identifying the level of cold damage occurrence was 62%, and the average accuracy rate of identifying cold damage in typical cold damage years was 93%. In summary, the definition and evaluation of the delayed chill injury indicator for the soybean growing season in Heilongjiang province has a high accuracy rate, easy access to the indicator, and strong practicality.

Key words: Soybean, Delayed-type chilling injury, Indices, Heilongjiang province